CHAPTER 4 FOOD MICROBIOLOGY - · PDF fileCHAPTER 4 FOOD MICROBIOLOGY 3/2/2005 1901(4a) 1 ... in cereals and grains. ... contamination of foods

CHAPTER 4 FOOD MICROBIOLOGY

3/2/2005 1901(4a) 1

Vegetative bacteria: Salmonella, E. coli, Vibrio, Shigella, Streptococcus, etc.100,000-to-1 kill; 145°F, 3 minutes; 150°F, 1 minute; 155°F, 15 seconds.Double wash fruits and vegetables (100-to-1 reduction). Spores: Clostridium perfringens, Bacillus cereus, Clostridium botulinum,

hot foodSurvive pasteurization. Hold ≥135°F.

Bacteria

Noroviruses, hepatitis A, rotavirusFrom human feces and vomit.Double wash fingertips.

Viruses

Aspergillus spp., Fusarium, penicillin on wholesale, stored grain and peanutsMost molds are spoilage. Cut off.Molds on grains and nuts can form toxins. Keep grains and nuts dry.

Throw out.

Molds

Trichina spp., Anisakis, beef tapeworm, Toxoplasma gondiiLive within animals and fish (in muscle, intestinal tract).1 to 10 will cause illness.Killed by freezing according to government-specified temperatures and times. Killed by cooking to 145ºF, 15 seconds.

Parasites

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FOOD MICROORGANISMS

Food Microorganisms

Introduction In order to develop sound safety standards and operating procedures, a basic understanding of microbiology is necessary. Microbiology is the study of small living systems (i.e., microorganisms), which include bacteria, yeasts, molds, viruses, and parasites. Some of these microorganisms are beneficial in food production and food processing. However, some microorganisms are pathogenic (cause disease and illness) and must be controlled or destroyed in food processing and preparation.

Parasites Parasites are organisms that live at the expense of the hosts (humans, animals, fish, and birds). In this text, parasites refer to protozoa (microscopic, single-celled animals with a defined nucleus) and helminths (small worms and their larvae).

Protozoa of common concern are Giardia lamblia and Entamoeba histolytica. Both of these protozoa cause diarrheal illness and intestinal discomfort of varying severity. They are often found in untreated or in inadequately chlorinated water supplies. They can become foodborne if water containing these protozoa is used to irrigate plants or wash food prior to service. Infected people and animals can also pass these protozoa in their feces to infect others, as with Toxoplasma gondii, a parasite whose original hosts are cats.

Helminths are parasitic worms. These worms are usually large enough to be seen without the aid of a microscope. However, a microscope is needed to detect their cysts and eggs. The parasitic worms of most concern in food are Trichinella spiralis, Taenia (tapeworms), and Anisakis spp.

Parasites are unique in that they can be destroyed by freezing according to government-specified temperatures and times. For example, Anisakis spp. in fish will be destroyed if the fish is held at -4ºF (-20ºC) for 7 days.

Molds Molds are larger than bacteria. Their presence can be seen as a cottony, powdery, or fuzzy patch on the surface of food and may be white or gray or highly colored.

Most molds are considered to be a spoilage problem. Examples of mold spoilage include: mold on cheese, fruits and vegetables, and bread. The mold growth alters the flavor and texture of the food products. If the mold growth is not extensive, the moldy part of the food can be trimmed and the food can be consumed.

Some types of mold are beneficial and are used to produce characteristic flavor in cheeses (e.g., Roquefort cheese) or produce soy sauce. Some types of mold are harmful and produce aflatoxins (carcinogenic compounds) when they grow in cereals and grains. The government tests for mold toxins in food and controls this hazard.

Viruses Viruses are not true living cells. They are acellular and have no cytoplasm, nucleus, cell wall, or cell membrane. Viruses are much smaller than bacteria and are composed of a protein coating around genetic material (DNA or RNA). Viruses are not able to reproduce unless inside a living cell (e.g., the Hepatitis A virus multiplies within human liver cells). Diseases and illnesses caused by viruses include colds, flu, and norovirus gastroenteritis.

Bacteria There are three basic forms of bacteria. These include: bacilli or rods, cocci, and spirilla. Cocci are round in shape and can be found as single cells, as chains (streptococci), in clusters (staphylococci, and in pairs (diplococci), or tetrads (sarcinae).

Bacterial cells are very small and measure approximately 0.05-2.0 x 2.0-10.0 microns or micrometers. One micron is 1/1,000 millimeter or 1/1,000,000 meter (10-6 m). A micron is also 1/25,400 inch. This means the length of 25,000 bacteria aligned end to end would be approximately one inch. The human eye can only resolve or see objects that are approximately 75 microns. Bacteria are 75 times smaller than the eye can see. Microscopes are needed to magnify bacteria so that they can be seen by the eye.

When millions of bacteria are present in a solution of clear broth, the broth becomes cloudy. In the same way, when bacteria multiply to numbers of 10,000,000 per gram of food, the food becomes slimy and is considered to be spoiled. Food with 10,000,000 spoilage bacteria per gram usually has off-flavor and odor and people judge it to be spoiled.

Yeasts Yeasts are much larger than bacteria. With a couple of rare exceptions, yeasts are not pathogenic (do not cause foodborne disease or illness).

Yeasts are used in food processing to produce bread, beer, and wine. When yeast grow in foods where their growth is not desired they cause changes in flavor, odor, and texture (e.g., yeast growth in fresh fruit juices and in ketchup).

Pathogenic vs. Non-pathogenic Microorganisms Pathogenic microorganisms cause disease or illness. The multiplication of pathogenic bacteria in foods does not usually change the odor or flavor of food.

Non-pathogenic microorganisms do not cause disease or illness and can be used to produce desirable changes in food (e.g. production of cheese and wine). The growth of non-pathogenic microorganisms causes food to spoil when they

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grow in food products where their growth is not desired. Non-pathogenic microorganisms produce acid, carbon dioxide, and other by-products that alter the texture, flavor and odor of food.

Primary Sources of Food Pathogens The intestinal tract of colonized humans and animals is a source of many pathogenic bacteria, which include: Escherichia coli, Salmonella spp. Shigella spp., Campylobacter spp., Staphylococcus aureus, Streptococcus, and Clostridia. Humans and animals also transmit viruses (e.g., hepatitis A virus and norovirus) through fecal contamination of foods. Parasitic infections are also spread through the fecal contamination of food products and water supplies. These include giardiasis and amoebic dysentery.

Soil and water are sources of molds, viruses, bacteria, and parasites. The following bacteria are commonly found in soil: Listeria monocytogenes, Clostridium botulinum, Clostridium perfringens, and Bacillus cereus. Water is a source of Vibrios, viruses, (e.g., hepatitis A virus and norovirus), and parasites (e.g., Giardia). Mold. can be found in both water and soil and they include Aspergillus, Penicillium, Fusarium, and others. Foods grown in soil and watered with river or lake sources will contain these pathogens, depending upon the contamination level of the water. Fish and seafood taken from rivers, lakes, and oceans may contain varying amounts of pathogenic microorganisms due to sewage treatment plant effluent as well as marine life contaminants.

Plants and plant products (e.g., fruits, vegetables, grains, and cereals) carry most of the same pathogens that are found in soil and water. Plants and plant products are also sources of molds and parasites.

Food utensils such as serving utensils, knives, cutting boards, slicing and chopping equipment will contain various kinds of microorganisms, depending on the food handled, the food handler, and the sanitization and storage of this equipment. For example, if a chicken containing Salmonella spp. is cut on a cutting board, the knife, cutting board, and hands of the food handler will all carry or become contaminated with this bacterium. These utensils (and the food handler's hands) must be thoroughly washed and sanitized to prevent the spread of this pathogen. Utensils that are stored in the open should be expected to contain airborne bacteria and molds.

Other sources of human contamination include the microflora on the hands, nasal cavities, and mouth of food handlers. Staphylococcus aureus is found in the nasal cavity (nose) and in infected cuts and wounds. Food handlers should never work with food if they have an open infected cut or boil.

Animal feeds may contain any one of a number of pathogenic microorganisms that include bacteria, molds, and viruses. It is well documented that animal feeds have been a source of Salmonella spp. in animals and poultry. The meat from these animals and poultry was then a source of Salmonella contamination and foodborne illness. Rodents and birds transmit microorganisms through their fecal contamination of grains and animal feed.

Air can carry many types of bacteria, viruses, and molds. Bacillus spp. and Micrococcus are able to endure dryness and can be carried in the air for many miles.

Control of Pathogens Table 4-1 (next page) lists some of the potential microbial pathogens in food. Note that all foods are a potential source of pathogens. There will never be a zero pathogen level in raw foods. However, they can, and must, be reduced to a safe level by the cook. Managers and food handlers must know the different types of pathogenic microorganisms of concern in food and food production. They must know their sources, conditions for optimal multiplication, and ways of preventing or inhibiting the presence and multiplication of these pathogens in foods to prevent foodborne illness outbreaks from occurring.

References: Frazier, W.C. and Westhoff, D.C. 1988. Food Microbiology.

3rd edition. McGraw-Hill, New York, NY. Jay, J. M. 2000. Modern Food Microbiology. 6th ed.

Chapman & Hall. New York, N.Y. Mossel, D.A.A., Corry, J. E. L., Struijk, C. B., and Baird, R.

M. 1995. Essentials of the Microbiology of Foods. John Wiley & Sons. New York, NY.

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Table 4-1 Potential Pathogens in Food

PATHOGENS

FOOD Infective Toxin and/or Spore

Producers Meat, Poultry, and Eggs Salmonella spp.

Campylobacter jejuni Escherichia coli Yersinia enterocolitica

Listeria monocytogenes Hepatitis A virus Trichinella spiralis Tapeworms

Staphylococcus aureus Clostridium perfringens Clostridium botulinum Bacillus cereus

Fin Fish

Salmonella spp Vibrio spp. Yersinia enterocolitica

Hepatitis A virus Anisakis Tapeworms

Staphylococcus aureus Clostridium botulinum Microbial by-products (Histamine poisoning)

Shellfish

Salmonella spp Vibrio spp. Shigella spp. Yersinia enterocolitica

Norovirus Hepatitis A virus

Staphylococcus aureus Clostridium botulinum Microbial by-products (Paralytic shellfish poisoning)

Fruits and Vegetables

Salmonella spp. Listeria monocytogenes Shigella spp. Escherichia coli

Hepatitis A virus Norovirus Giardia lamblia

Staphylococcus aureus Clostridium botulinum Bacillus cereus

Cereals, Grains, Legumes, and Nuts

Salmonella spp. Aflatoxins (mold)

Staphylococcus aureus Clostridium botulinum Bacillus cereus

Spices

Salmonella spp.

Staphylococcus aureus Clostridium botulinum Bacillus cereus Clostridium perfringens

Milk and Dairy Products Salmonella spp. Yersinia enterocolitica Listeria monocytogenes Escherichia coli

Campylobacter jejuni Shigella spp. Hepatitis A virus Norovirus

Staphylococcus aureus Clostridium perfringens Bacillus cereus

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Hold-serve-leftoversCook 130 to 212°FFood receiving

THE SPORE CYCLE (CLOSTRIDIA AND BACILLUS)

The Spore Cycle

Spores Some rod-shaped pathogenic bacterial cells, such as Clostridium perfringens, Clostridium botulinum, and Bacillus cereus, have the ability to form spores. The spore state is a period of no growth, similar to hibernation, in which the vegetative cell dries up. The reproductive system becomes encapsulated in a tough shell or membrane and the outer part of the old vegetative cell sloughs off. Spore capsules are very resistant to heat, chemicals, etc. The tough outside coat or membrane of spores is a survival mechanism brought on by some environmental stress or removal of nutrients necessary for multiplication. Spores have survived thousands of years in the tombs of Egypt and in the Antarctica.

Spores can change into vegetative bacterial cells when environmental conditions are present to support bacterial multiplication. When conditions are less than optimum, the vegetative cells again form spores, which are dormant until conditions are conducive to cell multiplication.

The Spore Cycle Both vegetative cells and spores are present in raw foods (e.g., fresh meat, fish, poultry, vegetables). Vegetables that have any contact with the ground will have Clostridium botulinum. These include onions, garlic, beans, tomatoes, cabbage, mushrooms, and potatoes. Meat can become contaminated during slaughter by the dirt on the hide. Fish found near shores or in bays consume sludge and have Clostridium botulinum in their intestinal contents. Rice and grain may be contaminated with Bacillus cereus. Meat and poultry are often contaminated with Clostridium perfringens because it is part of the normal intestinal flora of most warm- blooded animals.

During slow heating of food [i.e., taking longer than 6 hours to reach a temperature of 130°F (54.4°C)] vegetative cells can multiply. Cooking food to over 130°F (54.4°C) supplies sufficient heat, given adequate time, to pasteurize (i.e., inactivate to safe numbers) the vegetative cells of pathogenic bacteria and viruses. Vegetative cells are inactivated by most cooking processes, but spores survive and are actually activated by the heating process.

The activated spores germinate into vegetative cells and multiply during cooling or improper holding of food

especially rapidly at 85 to 120°F (29.4 to 48.9°C). These temperatures allow rapid bacterial multiplication. The spores, which have turned into vegetative cells, multiply rapidly, possibly producing toxic by-products (e.g., Clostridium botulinum, Bacillus cereus). When people eat the food containing the vegetative cells or toxin of these pathogens, they become ill with diarrhea, vomiting, or neurological symptoms and death, depending on the specific pathogen or toxin consumed. The vegetative cells and/or spores are eliminated in fecal material and return to the environment through waste disposal and sludge, to cycle again.

References: Frazier, W.C., and Westhoff, D.C. 1988. Food Microbiology,

3rd ed. McGraw Hill Inc., New York, NY. International Commission of Microbiological Specifications

for Foods. 1996. Microbial Ecology of Foods. Vol.5. Microorganisms in Food. Microbiological Specifications of Food Pathogens. Blackie Academic & Professional, New York, NY.

Jay, J. M. 2000. Modern Food Microbiology. 6th ed. Chapman & Hall. New York, N.Y.

Mossel, D.A.A., Corry, J. E. L., Struijk, C. B., and Baird, R. M. 1995. Essentials of the Microbiology of Foods. John Wiley & Sons. New York, NY.

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You control the process.Food Spoilers

Do not cause illness.Change the flavor, odor, and appearance of food.Inhibit growth of pathogens.

Food Process "Spoilers"?Used in the production of food products

(e.g., vinegar, bread, sauerkraut, cheese).They "spoil" the food.

Food PathogensCause illness.Often do not change the flavor, odor, and appearance

of food to indicate that the food is hazardous.If in doubt about how food was handled after cooking,

throw it out.854

HOW DO YOU KNOW IF FOOD IS HAZARDOUS OR SAFE?

Food Microorganisms - Spoilers, Process

Organisms, and Pathogens Microorganisms in Food There are useful as well as harmful microorganisms in food. Useful microorganisms are used to produce food products such as bread, cheese, wine, and soy sauce. Harmful microorganisms are those that cause spoilage in food products and pathogenic microorganisms that cause illness and disease.

Spoilers Food spoilage microorganisms do not cause illness. Spoilage organisms do, however, produce changes in the flavor, odor, color, and texture of food and food products. For thousands of years, spices have been used to mask the effects of spoilage microorganisms in order to make the food edible.

In raw food, spoilage microorganisms are usually present in much higher numbers than pathogens. Spoilage bacteria are able to grow more rapidly than pathogenic bacteria at temperatures below 80°F (26.7°C). Spoilage bacteria are also able to stop or inhibit the growth of many pathogens by competitive inhibition. Spoilage bacteria compete with pathogenic bacteria for nutrients and excrete by-products that discourage the growth of pathogens.

Spoilage microorganisms are a critical safety factor, especially in cooked food. When food is cooked, particularly for a long period of time or to the well-done condition, most of the spoilage microorganisms are destroyed. If a few pathogens remain in the food or if the food is recontaminated from utensils or hands, pathogens will be able to multiply to levels that make people ill, if given enough time at a favorable temperature.

Food Process Organisms Food process organisms are purposely cultured in food to produce desired flavors and textures. They are used to produce many food products such as: beer, wine, bread, cheese, soy sauce, and salami. The multiplication of food process microorganisms produces by-products such as acids, carbon dioxide, and alcohol, which help to preserve the food. If these same microorganisms are allowed to grow in foods where their presence is not desired, they are called spoilage microorganisms. Refrigeration and processing are often not required for these foods because the acidity or alcohol content of the products prevents the multiplication of pathogens.

Examples of foods produced by process microorganisms include: pickles, sauerkraut, yogurt, vinegar, cottage cheese, beer, wine, and bread. See Table 4-2 (next page).

Note: Histamine may also be produced during the multiplication of some process microorganisms. The presence of substantial amounts of histamine in food can cause adverse reactions in both sensitized and healthy individuals.

Pathogens Pathogenic microorganisms cause illness and disease. In many instances, they have no effect on the odor, taste, or appearance of the food. Many people even claim that the roast beef, cake icing, tuna salad, or other food that made them ill was the best they ever tasted.

References Frazier, W.C., and Westhoff, D.C. 1988. Food Microbiology.

4th ed. McGraw-Hill, Inc., New York, NY. Jay, J. M. 2000. Modern Food Microbiology. 6th ed.



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Table 4-2 Examples of Microorganisms Used In Processing Food

Organisms Substrates Products

Lactic acid bacteria, species of Leuconostock, Lactobacillus, Pediococcus, and /or Streptococcus.

Cabbage Cucumber Olives Vanilla beans Red Meat Milk and cream Milk Milk Milk

Sauerkraut Pickles Olives (green and ripe) Vanilla Sausages, (salami, Thuringer. Lebanon bologna, Cervelat, summer sausage, pepperoni) Sour cream, cultured butter, ghee Cultured milk, acidophilus, yogurt Cheese-unripened (cottage, pot, cream) Cheese-ripened (Cheddar, American, Edam, Cheshire

Penicillium roqueforti Unripened cheese Cheese (Roquefort, blue, Stilton, Gorgonzola

P. camemberti Unripened cheese Camembert cheese

Lactic acid bacteria Flour (dough) Sour dough bread and sour dough pancakes

Yeasts Malt Fruit Molasses Grain mash Flour (dough

Beer, ale, stout, lager, bock, porter, Pilsner Wine, vermouth Rum Whiskey Bread

Yeast with Acetobacter or Gluconobacter

Sugar, fruit, potatoes, honey, malt, grain alcohol

Vinegar

Halophilic bacteria Fish Nuoc-mam-ngapi

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The quality problem

SPOILAGE MICROOGRANISMS

Spoilage Microorganisms – The Real

Problem Spoilage Microorganisms There are many spoilage bacteria. Spoilage bacteria present an economic problem to the foodservice industry because of food losses.

As bacteria multiply and utilize protein, they break down its components, frequently producing unstable, volatile by-products. These compounds contribute to off-flavors and off-odors in food. Common by-products are ammonia and sulfur compounds.

Yeasts produce carbon dioxide, alcohol, and acids from fermentable sugars. If catsup is stored at room temperature after it is opened, it may become contaminated with yeast. When yeasts grow in catsup, the flavor changes due to the production of alcohol. Visible gas bubbles of carbon dioxide may appear in the catsup.

Mold growth causes spoilage of many foods, which include fruits, vegetables, meats, cheese, and cereals. The color, texture, flavor, and odor of foods are changed as a result.

Some spoilage bacteria, notably Proteus morganii, produce chemicals such as histamines that can cause a rapid onset of foodborne illness. Histamine is a bacterial breakdown product of proteins, particularly in fish and shellfish. Multiplication Requirements Some spoilage bacteria begin to multiply at approximately 23 to 25°F (-5 to -3.9°C). Meat thaws at about 28.5°F (-2°C). The significance of this is that spoilage microorganisms begin to multiply when the food is still frozen and some multiply actively at 32°F (0°C). Optimum multiplication occurs at 85 to 90°F (29.4 to 32.2°C). Multiplication of most bacteria stops at about 115°F (46.1°C), and bacterial cells are slowly inactivated as temperatures rise above this point.

Some pathogenic bacteria can begin to multiply at 29.3°F (-1.5°C), (Hudson et al., 1994). The USDA recommends that food storage refrigerators be maintained at 40°F (4.4°C) or below. The FDA recommends a temperature of 41°F (5°C) or below to prevent pathogenic bacterial multiplication. When refrigerators or coolers are set at 40 to 45°F (4.4 to 7.2°C), spoilage bacteria and bacterial pathogens (e.g., Listeria

monocytogenes, Yersinia enterocolitica, Aeromonas hydrophila, and Clostridium botulinum Type E) can multiply. Foodservice owners/managers who are concerned about both food safety and spoilage set their refrigeration systems to operate at 32 to 35°F (0 to 1.7°C), in order to slow bacterial spoilage and prevent multiplication of all pathogenic bacteria. Food spoils three to five times faster at 45°F (7.2°C) than at 32°F (0°C).

In order to maintain high quality and product safety, fresh seafood, poultry products, and fresh meat must be stored at 30°F (-1.1°C) in packaging material or closed containers to prevent surface drying and cross-contamination. If this temperature cannot be maintained during shipping and refrigerated storage, these products must be iced.

Enzyme Activity Enzymes are organic catalysts that increase the rate of chemical reactions. Enzymatic activity is slower as temperatures are decreased. However, they are still active at freezing temperatures over long periods of freezer storage.

Below 25°F (-3.9°C), food quality deteriorates due to enzymatic action. Food is not considered stable unless stored below -40°F (-40°C). Between 25 to -40°F (-3.9 to -40°C), natural enzymes are capable of causing nutrient losses (e.g., oxidation of ascorbic acid), changes in flavor and odor due to the oxidation of fat in food, and changes in protein components of food.

When meat is frozen at 28.5°F (-3.9°C), there are still tiny pockets of water in the food that gradually freeze as the temperature is reduced to -40°F (-40°C). Enzymatic reactions occur within these tiny pockets over a period of months to produce adverse effects in meat quality, primarily flavor.

Some raw foods are heated prior to freezing in order to inactivate enzymes, maintain quality, and extend the shelf life of the products. For example, most frozen vegetables are blanched (i.e., heated in steam or water just long enough to inactivate enzymes) prior to freezing. If vegetables are frozen unblanched, their quality decreases rapidly.

Freezer Temperature The quality retention of frozen products is maintained for longer periods of time if freezer units are set at -10°F (-23.3°C) or below. Freezer storage units should maintain stable temperatures. Fluctuations of temperature ±5°F (±2.8°C) are detrimental to the food quality due to the formation of large ice crystals that form when small ice crystals thaw and recrystalize during refreezing.

References: Hudson, J.A., Mott, S.J., and Penney, N. 1994. Growth of

Listeria monocytogenes, Aeromonas hydrophila, Yersinia enterocolitica on vacuum and saturated carbon dioxide controlled atmosphere-packaged sliced roast beef. J. Food Protect. 57 (3): 204-208.

International Commission of Microbiological Specifications for Foods. 1998. Microbial Ecology of Foods. Vol. 6. Microbial Ecology of Food Commodities. Blackie Academic & Professional, New York, NY.


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Mossel, D.A.A., Corry, J. E. L., Struijk, C. B., and Baird, R. M. 1995. Essentials of the Microbiology of Foods. John Wiley & Sons. New York, NY

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HACCP process control vs. finished product sampling

1339

• Commercial sterilization: destruction of Clostridium botulinum spores• Foodservice pasteurization: reduce infective microorganisms to a safe

level• Raw or rare food must have supplier certification• Refrigeration holding: 41ºF, 7 days (or 10 multiplications equivalent• Heating: 41 to 130ºF in <6 hours• Salmonella 5D pasteurization: 130ºF, 86.45 minutes; 140ºF, 8.65 minutes;

150ºF, 51.9 seconds; 160ºF, 5.19 seconds• Hot holding: 130ºF (safety); 135ºF (FDA)• Cooling:

USDA - 120 to 55°F, <6 hours; continue to 40°F to prevent spore outgrowth and multiplication of Clostridium perfringens; FDA - 135 to 70°F within 2 hours, followed by cooling to ≤41°F, ≤6 total hours

• Thermally resistant microorganisms

FOOD SAFETY MICROBIOLOGY

Food Safety Microbiology

Microbiological Foundations for HACCP-Based Process Control When food is purchased, raw, unprocessed food must be assumed to be contaminated with low levels of infective and spore-forming pathogens. Periodically, there may be levels of pathogen contamination that can cause an immediate hazard. Most foodservice cooking processes do not heat food long enough to reduce spore contamination, but do provide sufficient thermal energy to inactivate the vegetative cell forms of pathogens to a safe level.

Process Control vs. Finished Product Microbiological Control In the past, the food microbiologist has relied on finished product sampling procedures to assure the safety of the food. HACCP principles require that the pathogen level in the finished product should be below normal microbiological detectable limits. To assure the safety of a product (i.e., an infective pathogen level of 1 microorganism per 100 grams of food) through microbiological testing, the total output of the process would need to be evaluated. This is impractical. The commercial canning industry has determined times necessary for thermal destruction of spores of Clostridium botulinum in cans of food. (Processing times and temperatures are based on reducing the number of spores of C. botulinum from 1012 to 1.) When commercial canning processes operate according to these recognized safety guidelines, the safety of unopened cans of foods stored at room temperature is assured.

Pasteurization in Foodservice vs. Processing D-value is the time at a specific temperature for the reduction of the microbiological population by 1 log or a factor of 10 to 1. In designing a HACCP-based safety-assured process, the object is to identify the approximate incoming load of pathogens and then apply sufficient heat to reduce this population of pathogens by a specified amount. In chilled food processing plants, the USDA has identified D-values (i.e., times at specified temperatures) required for preparing meat and meat products. Salmonella spp. has been used as the test or control organism; times and temperatures for processing are based on reducing a population of 100,000 Salmonella cells to 1.

It is important not to set processing standards that force foods to be over-processed without really reducing the risk. The highly heat-resistant Salmonella senftenberg 775 W, which is very difficult to inactivate, is not included as a test organism. S. senftenberg has only been implicated in one foodborne illness, as far as is known, and is therefore not considered to be a threat on which food process standards should be based.

The USDA has also identified that the process should be able to reduce the population of Listeria monocytogenes by 10,000 to 1. Listeria monocytogenes is slightly more heat resistant than Salmonella. However, the required 105 Salmonella cell reduction process will inactivate 104 cells of Listeria monocytogenes. It is therefore possible for processing operations to continue using existing processing standards based on Salmonella spp. reduction.

Foodservice Food Pasteurization Food used or prepared in foodservice units usually has very low levels of pathogens and is not subjected to the same degree of mishandling that occurs when commercial processors of food release their products for distribution and sale in the retail marketing system. In foodservice, it is very unlikely for processed food to have more than 1,000 Salmonella spp. Under most conditions, healthy people can eat 1,000 Salmonella and not become ill. If cooking/heat processing times for destruction of 100,000:1 Salmonella are used, pasteurization should be adequate. Temperatures and times necessary for this 100,000:1 Salmonella reduction are: 130°F (54.4°C) for 86.43 min.; 140°F (60.0°C) for 8.64 min.; 150°F (65.6°C) for 0.864 min.; and 160°F (71.1°C) for 0.0864 min. The reason that food must be cooked at the retail level is basically a result of HACCP failures by persons who grow, harvest, and process raw ingredients.

Serving Rare or Raw Food When raw food, such as fruits and vegetables, are washed, there is some reduction in the microbial population. If water alone is used, the population can be reduced 10 to 1 or more. If the products are washed in a 200-ppm chlorine solution or 5% acetic acid at a temperature of 130 to 140°F (54.4 to 60°C), there will be a 100 to 1 reduction. While chemical disinfectants are used in the food processing industry, they should not be used in the retail sector. If these foods have an unacceptable microbial population, the source of supply should be changed.

If rare and raw food is served in foodservice establishments, suppliers must be required to provide microbiological certification that indicates the pathogen level of the products is below that which is hazardous to the health of people.

Other Process Controls In addition to thermal inactivation, there are other controls that must be in place. These include the following:

1. The sanitizing process must reduce the pathogen population to a low enough level to avoid a cross-contamination problem. The sanitation process provided by reputable chemical supplies must meet the government requirement of 100,000-to-1 microorganism reduction (99.999% reduction).

2. The multiplication rate of microorganisms at refrigeration and elevated temperatures must be

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understood so that the food will not be held too long at hazardous temperatures. It is not possible to totally halt pathogen multiplication unless food is stored below 29°F (-1.5°C). It is reasonable to limit multiplication to no more than 10 generations.

3. Prevent multiplication of Clostridium perfringens during heating by cooking food from 41 to 130°F (5 to 54.4°C) in less than 6 hours.

4. Provide adequate pasteurization for the number of microorganisms present in the food (as mentioned above).

5. Hold hot food above 130°F (54.4°C) to prevent the multiplication of pathogens. [The FDA Food Code recommends holding food at or above 135°F (57.2°C).]

6. Cool food continuously from 120 to 55°F (48.9 to 12.8°C) in less than 6 hours, then continue to cool food to 40°F (4.4°C) to prevent spore outgrowth and multiplication of Clostridium perfringens (according to USDA Guidelines). [The FDA Food Code recommends cooling potentially hazardous food from 135 to 70°F (57 to 21°C) within 2 hours; followed by cooling to 41°F (5°C) or below within with in a total time of 6 hours or less.]

Infective and Spore Control Process Design It is not necessary to check a process for all the pathogenic microorganisms. The following organisms represent the control standards at various temperatures at which to base process design:

1. Growth at refrigeration temperature: Listeria monocytogenes is the organism of choice because it is very common in the environment and will multiply under all types of environments beginning at a temperature of 29°F (-1.5°C). Clostridium botulinum Type E, which begins to multiply at 38°F (3.3°C), is also a potential hazard if food, particularly vacuum packaged fish, is kept for a long time (over 21 days at above 38°F (3.3°C) after it has been cooked.

2. Control of growth at 60 to 127.5°F (15.6 to 53.1°C): Clostridium perfringens is the microorganism of choice for control in this temperature range. The reason for this is that it multiplies faster than any other microorganism in this range.

3. The organism of choice for destruction in a temperature range of 130 to 160°F (54.4 to 71.1°C) is Salmonella, because if Salmonella is reduced 100,000 to 1, all of the parasitic and vegetative cells will also be controlled. There is some speculation that viruses may be more thermally resistant than Salmonella. However, it appears that viruses can be partially controlled by correct hand washing and prevention of cross-contamination of the food.

Thermally Resistant Organisms Staphylococcus aureus and Streptococcus spp. are more resistant than Salmonella spp. to thermal inactivation. It can be expected that low levels will survive the cooking process, if there are more than 100 cells per gram in the raw product.

If food is properly refrigerated below 41°F (5°C), then neither of these organisms can multiply, and low numbers of these

microorganisms can be tolerated in the final product without becoming a hazard to the health of consumers.

Summary 1. Any food can become hazardous. 2. The sources of the hazard(s) must be assessed. 3. It is important that suppliers have HACCP programs and

pathogen certification so that only very low levels of pathogens are present in incoming food products.

4. Critical process controls must be used to prevent hazards from causing a foodborne illness.

5. Measurement of processing time and temperature must be used to assure that processing and preparation procedures are sufficient to ensure safety.

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BACTERIA

Bacteria

Bacterial Structure, Identification, and Classification Bacteria are so small that they can be seen only by using a microscope. They measure 0.05-2.0 by 2.0-10.0 micrometers. Bacteria are structurally simple cells that contain a nuclear region in place of a true nucleus. The shape and size of a bacterial cell is one of the first clues to its identification. Bacteria can have the shape of a rod, a sphere, a comma (Vibrio), or a spiral. Some bacteria are pleomorphic and can assume more than one shape. Some types of bacterial cells contain flagella or tail-like structures, which give the cells mobility. When viewed through a microscope, the shape of bacteria and their cellular association in chains, clusters, and tetrads is important for their identification and classification.

Most bacteria multiply by a process called binary fission, a division process that results in two equal cells forming when one bacterial cell divides. Some bacteria divide by budding. Budding results in cells of unequal size.

Spore-Forming Bacteria The Clostridium and Bacillus, which are members of the family Bacillaceae, are capable of forming spores (endospores) when subjected to adverse conditions. The process is called sporogenesis. Spores have no detectable metabolic activity, and are able to survive for thousands of years as a resting form of the cell. Bacterial spores are more resistant to heat, drying, and chemicals than their viable cell forms.

Spores in food become activated when food is cooked. For example, the standard laboratory procedure for activating spores of Clostridium perfringens is to heat the spore culture in a beef broth media to 176°F (80°C) and hold the culture at this temperature for 20 minutes. Activated spores then undergo a process of germination to form viable (living) cells when cooled to suitable growth temperatures of 80 to 120°F (26.7 to 48.9°C).

In order to destroy the thermally resistant forms of Clostridium botulinum Types A and B, the standard inactivation procedure for spores, used by the canning industry, is to heat can contents of low-acid food to a temperature of 250°F (121.1°C) for 3 minutes at the coldest spot within the can.

Toxin-Producing Bacteria Some bacteria produce toxins as a waste product when they multiply. The toxins may be excreted into the surrounding medium or food (exotoxins), or retained within the cell (intracellular toxins). They are released when the cells disintegrate in the human intestine after contaminated food is eaten. Exotoxins produced by Staphylococcus aureus and Bacillus cereus are heat resistant and require temperatures above 212°F (100°C) for many minutes for their destruction or inactivation. Fortunately, the toxins of Clostridium botulinum, which are extremely lethal, are relatively easily destroyed by heat. If these toxins are heated to 185°F (85°C) for 5 minutes, they are inactivated. When foods are cooked, toxins may not be destroyed and their production in food must be prevented.

Toxins are also classified as to their physiological effect (i.e., effect on humans or animals if consumed). For example, toxins that cause gastroenteritis or inflammation of the lining of the stomach and intestines, such as the toxin produced by Staphylococcus aureus, are called enterotoxins. Toxins that affect the central nervous system, such as those produced by Clostridium botulinum, are termed neurotoxins.

Growth Requirements All bacteria have relatively specific requirements for growth. These include food or nutritional requirements, temperature, moisture, atmosphere (i.e., ability to multiply with or without oxygen), and acidity. Requirements for growth vary with the kind of bacteria and within strains of a species of bacteria.

Methods of Control Bacteria can be killed with heat, chemicals, or ionizing radiation. High temperatures denature proteins and nucleic acids by breaking their hydrogen bonds. When this happens, the proteins unfold and the double stranded nucleic acids (DNA) separate. The bacterial cells are no longer capable of reproduction. Ionizing radiation inactivates vegetative cells by causing chemical changes within the nitrogenous bases (units) of nucleic acids.

Groups of Bacteria Important in Food Microbiology Bacteria are often grouped according to temperatures of growth. Table 4-3 tabulates these different growth temperatures.

Table 4-3 Groupings of Microorganisms Based on Temperatures of

Growth *

Type Minimum Temp.

°F

OptimumTemp.

°F

MaximumTemp.

°F Psychrophiles 32 50 68 Psychrotrophs 41 77 95 Mesophiles 1-50 36-99 113 Thermotrophs 59 107-115 122 Thermophiles 104 113-131 140-176

* Adapted from Essentials of Microbiology of Foods by

D.A.A. Mossel. Bacteria are sometimes grouped according to their metabolic by-products and other conditions that either support or allow their growth. Many bacteria possess more than one of these

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common characteristics, as is indicated by the following types or groups.

Acid-forming bacteria are capable of metabolizing sugars, other carbohydrates, and alcohol to form organic acids. Acid-forming bacteria include: lactic acid-forming bacteria (e.g., Lactobacillus acidophilus, Streptococcus lactis), acetic acid-forming bacteria (e.g., Acetobacter, Gluconobacter), butyric acid-forming bacteria (e.g., Clostridium), and proprionic acid-forming bacteria (e.g., Proprionibacterium).

Proteolytic bacteria produce enzymes that are capable of decomposing proteins into foul-smelling compounds such as hydrogen sulfide, amines, indole, and amino acids. Clostridium putrefaciens and Clostridium botulinum Type A are examples of proteolytic bacteria.

Lipolytic bacteria produce enzymes that are capable of splitting fats into fatty acids and glycerol. Pseudomonas fragi and Staphylococcus aureus, if present in raw milk, produce heat-resistant lipases, which may survive pasteurization [161°F 72.2°C)] and cause development of off-flavors in milk during distribution.

Saccharolytic bacteria produce enzymes that split complex sugars and starches into simple sugars or smaller carbohydrates. Examples of saccharolytic bacteria are Bacillus subtilis and Clostridium butyricum.

Pectolytic bacteria produce enzymes that cause pectin to hydrolyze or split into smaller molecules. As a result there is softening of plant tissues and loss of gelling capability of fruit juices. Erwinia carotovora causes raw fruits and vegetables to have a water-soaked appearance, a soft, mushy consistency, and often, bad odor.

Thermophilic bacteria, or thermophiles (i.e., high-temperature-loving bacteria), have an optimum temperature for growth of 113°F (45°C), but can grow at 132°F (55.6°C) and above. Bacillus stearothermophilus is an example of a thermophilic bacteria that causes flat sour spoilage of canned foods stored at high temperatures. These spoilage bacteria will multiply in food held at hot holding temperatures [135 to 150°F (57.2 to 65.5°C)].

Thermotrophic bacteria, or facultative thermophiles, are bacteria that are tolerant of high temperatures. An example of a thermotrophic bacteria is Bacillus coagulans, which causes flat sour spoilage of acid foods such as tomatoes and tomato juice. The spore forms of both thermophilic and thermotrophic bacteria can survive ordinary cooking and cause food to spoil, even if held at 140°F (60°C)

Mesophilic bacteria are bacteria that grow in the middle temperature range. Their optimal temperature for growth is 86 to 99°F (30 to 37°C). Most foodborne pathogens (e.g., Shigella spp., Staphylococcus aureus, Salmonella spp.) grow rapidly in this temperature range.

Psychrophilic bacteria are those bacteria whose optimum temperature for growth is 50°F (10°C) or lower. Vibrio parahaemolyticus, Vibrio cholerae, and Vibrio vulnificus are examples of psychrophilic bacteria that may be found on fish and seafood.

Psychrotrophs have an optimal temperature for growth of 77°F (25°C) but can grow at 41°F (5°C) or lower. Examples

of psychrotrophic bacteria include Pseudomonas spp. which cause spoilage in meat and poultry.

Halophilic bacteria or halophiles require certain minimal concentrations of dissolved salt (sodium chloride) for growth. Salt requirements vary from as low as 2% to as high as 30% salt. Halobacterium require salt for growth.

Halotolerant bacteria are salt tolerant and can grow with or without salt. Staphylococcus aureus can grow well without salt, but it can grow well in 7 to 10% concentrations of salt. Some strains grow in 20% salt concentrations.

Osmophilic and saccharophilic bacteria are bacteria that grow in high concentrations of sugar. Most bacteria that are called osmophilic are merely sugar tolerant (e.g., some Leuconostoc spp.).

Pigmented bacteria produce various colors on or in foods as a result of their growth in foods. An example of a pigmented bacteria is the rust-colored Lactobacillus plantarum, which discolors cheese.

Slime- and rope-forming bacteria cause ropiness in milk and beer and produce a slimy surface growth on various foods. Enterobacter aerogenes causes ropiness in milk. Bacillus mesentericus causes rope in bread, and the bread smells like ripe cantaloupe.

Gas-forming bacteria produce carbon dioxide or both carbon dioxide and hydrogen. Some genera of Leuconostoc, Lactobacillus, Escherichia, Enterobacter, Proteus, Bacillus, and Clostridium are gas-forming bacteria.


Fourth edition. McGraw-Hill, New York, NY. Jay, J.M. 2000. Modern Food Microbiology. 6th edition.

Chapman & Hall Inc., New York, NY. Prescott, L. M., Harley, J. P., and Klein, D. A. 1996.

Microbiology. W. C. Brown. Dubuque, IA. Mossel, D.A.A., Corry, J. E., Struijk, C. B., and Baird, R.

1995. Essentials of the Microbiology of Foods. John Wiley and Sons, New York, NY.

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YEASTS

Yeasts

General Characteristics Yeasts have been defined as fungi with a unicellular form. There are over 350 species of yeast, which are classified into 39 genera. Yeasts are microscopic organisms that are differentiated from bacteria by their larger cell size, and by their production of buds during the process of division. Yeast cells may be oval, elongated, elliptical, or spherical in shape. Their size varies from 5 to 8 millimicrons in diameter. Some yeasts may be as large as 100 millimicrons in length. Older yeast cells tend to be smaller than young multiplying cells.

Most yeasts are not pathogenic. They are important in food manufacturing (e.g., bread, beer) but can cause foods to spoil when their multiplication is not desired (e.g., fermentation of catsup and fresh fruit juices).

Candida albicans is a pathogenic yeast. It can invade the epidermis (skin) and mucous membranes of the body, particularly those of the mouth, intestinal, urinary and reproductive tract. It is of concern for infants (a cause of thrush) and for immune-compromised individuals.

Some yeasts are pigmented or colored. When these pigmented yeast multiply in food, streaks of color provide evidence of their presence (e.g., red, pink, black, or yellow streaks of color) in food products.

Reproduction On the basis of reproduction, yeasts can be separated into four groups. Only two of these groups contain yeasts involved with foods. One group of yeasts found in food is called Ascomycetes, or true yeasts. True yeasts reproduce by sexual reproduction. True yeasts produce asexual spores and chlamydospores. Chlamydospores are very durable and are produced when yeasts find environmental conditions unfavorable for multiplication.

The other group of yeasts found in food is asporogenes yeasts (i.e., false, or wild yeasts) because they do not display sexual reproduction and form no spores. Vegetative reproduction refers to asexual reproduction. All yeasts can reproduce asexually, and this is the only method for asporogenes yeasts.

The usual vegetative (asexual) reproduction is by budding. Some yeasts reproduce by fission or by an intermediate system called bud fission. If a new cell or bud appears at the short

end of the mother cells, it is called polar budding. If the bud forms at both ends, it is bipolar budding. When buds appear any place on the mother cell this is called multilateral budding.

Yeasts can change in their physiological characteristics, especially the true yeasts, which have the sexual method of reproduction. These types of yeast can mutate or be bred to new forms. Most yeast can adapt to conditions, which previously would not have supported their multiplication. For example, there are a large number of strains of Saccharomyces cerevisae that are best suited for different uses (e.g., bread strains, beer strains, wine strains and high-alcohol-producing strains).

Multiplication Requirements Yeasts multiply over a wide range of pH, alcohol, and sugar concentrations. In general, yeasts require sugar as a source of energy. As a result of this metabolism by-products of carbon dioxide and alcohol are produced. This process is called fermentation. Other yeasts, such as film yeasts, oxidize organic acids and alcohol. Yeasts also have nutritional requirements for a source of nitrogenous compounds and minerals. This requirement varies with the type and strain of yeasts.

Most yeasts multiply best with a plentiful supply of water or moisture. Some yeasts are capable of multiplying in high concentrations of salt and sugar. Yeasts are classified as ordinary yeasts if they do not multiply in high concentrations of sugar and salt and as osmophilic yeasts if they are capable of multiplication in these conditions. The lower limits of water activity (aw) range from 0.88 to 0.94 for ordinary yeasts. Osmophilic yeasts can multiply in media such as syrups with an aw as low as 0.62 to 0.65. Each type of yeast has its own characteristic optimal aw and range of aw for multiplication.

The range for optimal temperature for multiplication of most yeasts is 77 to 86°F (25 to 30°C). The maximum multiplication temperature ranges from 95 to 117°F (35 to 47°C). Some kinds of yeast multiply at 32°F (0°C) or less.

The pH for optimum multiplication of most yeasts is in the acid range of 4 to 4.5 pH. Yeasts do not multiply well in alkaline conditions, unless they adapt to these conditions. Most yeasts multiply best under aerobic conditions, but some types can multiply slowly, anaerobically.

Methods of Control Yeasts are destroyed when heated to temperatures of 131 to 149°F (55 to 65°C) for a few minutes. Most cooking procedures and pasteurization procedures reach temperatures and times that are sufficiently high enough and long enough to inactivate yeasts. However, yeasts can recontaminate food products. Care must be taken to prevent this from occurring. After products have received these treatments, they should be covered and sealed in containers to prevent recontamination, and stored at refrigerator or freezing temperatures.

Yeasts in Food Products Yeasts are associated with nearly all types of food products. Yeasts cause spoilage of various food products, particularly those containing sugars, brined foods, and fruits. Yeasts are also important in processing of foods: in the fermentation of alcoholic beverages, the baking industry (i.e., bread production), and as a single-cell protein source.

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Fresh vegetables, meat, poultry, and cheese often contain yeasts, but usually bacteria in these foods out-number and out-multiply the yeasts. If bacteria are destroyed or their multiplication is inhibited, yeasts can dominate. For instance, products with high concentrations of sugar such as honey and molasses will not support the multiplication of most bacteria, but will support the multiplication of some yeasts such as Saccharomyces rouxii, which is known to cause spoilage in these products.

Groups of Yeast Important in Food Microbiology True Yeasts Saccharomyces reproduce by budding and ascospore formation. The most important species of this group is Saccharomyces cerevisiae has many uses in food production. Special strains are used to leaven bread, to produce wine and beer, and for the production of alcohol and glycerol (i.e., glycerine). Other species of Saccharomyces include: S. carlbergensis, which is used to make beer; S. fragilis and S. lactis, which ferment lactose in milk; and S. rouxii and S. mellis, which are osmophilic and multiply in high sugar solutions such as maple syrup and honey.

Schizosaccharomyces reproduce by fission and ascospore formation. This group of yeast has been found in tropical fruits, molasses, soil, and honey.

Zygosaccharomyces are capable of multiplication in high concentrations of sugar, and cause spoilage of honey, syrups, and molasses. Strains of this group are also used in the production of soy sauce and some wines.

Pichia oxidize alcohol to form films on wine and beer (e.g, P. membranaefaciens).

Hansenula oxidize alcohol and organic acids and form films on beer, sauerkraut, and other brined products.

Debaryomyces are very salt tolerant and form films on meat brines. D. kloeckeri causes spoilage when it multiplies on cheese and sausage.

Hanseniaspora are lemon-shaped yeasts that multiply in fruit juices and wine to produce compounds, which give these products off-flavors. Nadsonia is one of these species.

False Yeasts Torulopsis are round or oval, fermentative yeasts that reproduce by budding. T. sphaeric causes spoilage in milk and dairy products due to its ability to ferment lactose. Other species cause spoilage of sweetened condensed milk, fruit-juice concentrates, and acid foods.

Candida form films and are capable of causing spoilage in foods high in acid and salt. C. lipolytica can spoil margarine and butter. Some strains have benefit in food production. For instance, C. utilis is grown for food and feed, and C.krusei is sometimes grown with dairy starter cultures to maintain activity and increase longevity of lactic acid bacteria.

C. albicans is pathogenic and has the potential of being spread by foodservice personnel who are carriers and who use poor personal hygiene. A typical mode of transmission would be failure to wash hands after using the toilet and then touching food items that receive no heat treatment prior to consumption (e.g., salads and cold hors d'oeuvres).

Brettanomyces produce high amounts of acid and are used in the late fermentation of some beers and wines in order to produce characteristic flavor. B. bruxellansis and B. lambicus are typical of this species.

Trichosporon multiply best at low temperatures. These yeasts are found on various foods such as fresh shrimp, crab, beef, butter, cheese, fruit, fruit juice and rice. T. pullulans is a common species.

Rhodotorula multiply on foods to produce red, pink, or yellow spots (e.g., colored spots on meats or pink areas in sauerkraut).

References: Chin, J. ed. 2000. Control of Communicable Diseases in

Man. 17th edition. American Public Health Assoc. Washington, D.C.

Frazier, W.C. and Westhoff, D.C. 1988. Food Microbiology. Third edition. McGraw-Hill, New York, NY.

Jay, J.M. 2000. Modern Food Microbiology. 6th edition. Chapman & Hall Inc., New York, NY.

Mossel, D.A.A., Corry, J. E., Struijk, C. B., and Baird, R. 1995. Essentials of the Microbiology of Foods. John Wiley and Sons, New York, NY.

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MOLD

Mold

General Characteristics Mold is a term that is applied to certain multicellular, filamentous fungi whose growth on food is readily recognized by its fuzzy or cottony appearance. Molds grow rapidly and can cover several inches of area in a few days. Mold growth commonly appears white but may be colored or smoky grey. Reproduction The total mass of the mold or any large single portion is called the mycelium. The mycelium is composed of branches or filaments called hyphae. The hyphae may be submerged (i.e., growing within the food), or aerial (i.e., growing into the air above the food). Molds are divided into two groups on the characteristics of their hyphae. Septate molds have cross walls that divide the hypha into cells. Nonseptate molds have hyphae that consist of cylinders without cross walls. The nonseptate hyphae have nuclei scattered throughout their length and are considered multicellular.

Reproduction of molds is chiefly by means of asexual reproduction. At the time of asexual reproduction, sporangiophores or conidophores are formed, which produce sporangiaspores or conidia at their tips. Molds also produce other asexual spores. Chlamydospores are formed when a thick wall develops around any cell of the mycelium. Arthrospores are formed by some molds that produce septate mycelium. (Septate mycelium are capable of separating into units or segments.) Chlamydospores and arthrospores are more resistant to changes in environmental conditions. Molds also reproduce by sexual means when they form either ascospores, oospores, or zygospores.

Growth Requirements Most molds require less available moisture than most yeasts and bacteria. (See Table 4-4.) A total moisture content below 14-15% in foods such as flour or dried fruits prevents mold growth.

Most molds grow well at ordinary temperatures. The optimal temperature for growth is 77 to 86°F (25 to 30°C). A number of molds are psychrotrophic and grow well at refrigeration temperatures. Some molds grow at temperatures below freezing [i.e., at 14 to 23°F (-10 to -5°C)]. A few molds are thermophilic and have a high optimal temperature.

Table 4-4 Approximate Minimum Water Activity (aw) Values for the

Growth of Microorganisms in Foods *

Organism aw Most spoilage bacteria 0.90 Most spoilage yeasts 0.88 Most spoilage molds 0.80 Halophilic bacteria 0.75 Xerophilic molds 0.61 Osmophilic yeasts 0.61

* Adapted from Jay, J.M. 2000. Modern Food Microbiology. Molds are aerobic. They require oxygen for growth. Molds grow over a wide pH range (i.e., pH 2 to 8.5). Molds grow on many foods. Molds grow on moist and dry foods, acid and non-acid foods, and in foods that are high or low in sugar and salt.

Mycotoxins Although most molds are not considered to be pathogenic, some produce mycotoxins that are very toxic and are a health hazard. Mycotoxins produced by molds generally have an effect on liver and kidney functions. Some mycotoxins can have an effect on the central nervous system. A mycotoxin of current concern is aflatoxin. Aflatoxin is produced when Aspergillus flavus grows in grains, nuts, and legumes that contain higher levels of moisture. Aflatoxin is a liver carcinogenic compound. Aflatoxins are destroyed in grains and cereals by heat processing products at high temperatures above 250°F (121.1°C).

Methods of Control Certain chemical compounds are mycostatic (i.e., inhibit mold growth). Sorbic, proprionic, and acetic acids are used in food products for this purpose. Initiation of mold growth is slow when compared to bacteria or yeasts, and the growth of these microorganisms competitively inhibit mold growth. If cooked, pasteurized, or other heat-processed foods are contaminated by molds, their growth in foods will be quite rapid. Care must be taken to prevent moldy food products from contaminating fresh foods.

Equipment surfaces, refrigeration units, and freezers must be cleaned and sanitized regularly to prevent mold growth and contamination.

Vegetative molds are destroyed during cooking and heat processing, but some mold spores can survive heat processing. Food that is excessively moldy should be discarded. If there is any doubt about the safety of molded food, it should be discarded.

The FDA has specified that if there is mold on cheese, the mold on the cheese must be cut off. An additional 1/2 inch of cheese beneath the mold should also be cut off and discarded.

Molds in Food Products Molds are considered to be spoilage organisms in food products where their growth is not desired. The appearance of mold on products is an indication of spoilage, but molds can degrade food products before growth is evident.

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Molds are also useful in the processing of many foods such as cheese and soy sauce. Their enzyme systems have been isolated and used for food processing (e.g., isolation and extraction of amylases, pectinases, proteinases, and lipases). Some molds are used to convert waste products into usable animal food products. Some molds are a source of vitamins. Some molds are a source of antibiotics such as penicillin.

Groups of Molds in Food Products This is a partial list of molds of importance in food products.

Aspergillus appear yellow to green to black on a large number of foods. They have septated mycelia and produce conidia (i.e., free spores). The growth of Aspergillus flavus in cereals, grains, legumes, and nuts produces aflatoxin. Other species of Aspergillus are used to produce citric acid and proteases. Aspergilli are found on cakes, fruits, vegetables, meats, and other products. Aspergillus glaucus is a common cause of mold on hams and sausage.

Cladosporium are composed of septated mycelium and produce conidia. One species, C. herbarum, grows on connective tissue or fat covering of meat when refrigerated for several days, producing black spots on meat.

Fusarium (Gibberella) The mycelium produced by the growth of these molds produces a cottony growth that has tinges of pink, purple, and yellow. They cause spoilage of many fruits and vegetables, including "neck rot" of bananas. Some Fusarium produce T-2 toxin (a neurotoxin) and vomitoxin.

Geotrichum are yeastlike fungi that are usually white. They have septated mycelium and reproduction occurs by fragmentation of the mycelium into arthrospores. They are sometimes referred to as "dairy mold" since they produce flavor and odor in many types of cheese. They are also referred to as "machinery molds" since they build up on food-contact equipment in food-processing plants. The mold is killed during thermal processing of the food, but the hyphae can be determined by microscopic examination. The presence of mold in canned foods is considered to be an adulterant and indicates inadequate sanitation during processing. Geotrichum also infect ripe fruits.

Penicillium produce septate mycelia and form conidia. The growth of this species of mold produces blue to blue-green colors on food. P. digitatum causes green mold rot, and P. italicum causes blue mold rot of citrus fruits. Penicillium expansum causes soft, blue mold rot of apples, peaches, and pears. Species of Penicillium are found growing on the fat and connective tissue of meat stored in the refrigerator and in moldy bread. Other species of Penicillium are used to produce Camembert and Brie cheese. P. Roqueforti is used to produce Roquefort, Gorganzola, and other blue-veined cheeses. Some species of Penicillium are used to produce antibiotics such as penicillin. Some people are allergic to this mold.

Rhizopus have nonseptated mycelia and produce spores. They are very widespread in nature and can be found growing on bread, cakes, preserves, and fruits. Rhizopus stolonifer is often called bread mold. Some species of Rhizopus are used to convert starch to alcohol.

Thamnidium have nonseptated mycelia and produce spores. They are sometimes found on refrigerated meats, especially hind quarters that have been refrigerated for a long period of time, where they cause "whiskering" of the meat. They are also found in decaying eggs.

Byssochlamys produce ascospores. The ascospores of these molds are heat resistant and produce spoilage in high-acid canned foods as this organism can grow at low oxygen levels. They exist in soils and can be recovered from ripening fruits, especially grapes. They are the most heat resistant of all spoilage molds.


Third edition. McGraw-Hill, New York, NY. Jay, J.M. 2000. Modern Food Microbiology. 6th edition.

Chapman & Hall Inc., New York, NY. Mossel, D.A.A., Corry, J. E., Struijk, C. B., and Baird, R.


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VIRUSES

Viruses

General Characteristics Viruses are much smaller than bacteria. They are too small to be seen with a light microscope but can been seen with an electron microscope. They vary in size from 0.01 to 0.45 micrometers. Virus particles contain a nucleic acid (either DNA or RNA, which are genetic information), and a protein coat. Viruses are not capable of multiplying outside a host cell. If not present in a host cell, viruses will retain or lose their infectious potential.

When a virus particle attaches to and invades a susceptible host cell, the nucleic acid core and the protein coat separate. The nucleic acid from the virus then directs the host cell's "machinery" to make hundreds to thousands of virus particles. In this way, viruses multiply and are able to destroy host cells. If a significant number of cells stop or cease their special functions for any length of time as a result of the virus infection, illness may result. If enough cells in a vital organ cease to function, as with hepatitis A virus and liver cells, death results.

Immunity Most viruses transmitted in foods seldom kill their hosts. Instead, the host throws off the infection by means of nonspecific immunity and antiviral antibodies. Antibodies are slow to develop and often do not take effect until after the viral infection has run its course. The biggest effect of the antiviral antibody is to usually prevent recurrences of infection by the same virus. This is called immunity.

Methods of Transfer Viruses that cause foodborne illness can be transferred on food, usually by fecal contamination caused by foodservice workers who do not wash their hands properly after using the toilet, and by water polluted with raw sewage. Rotavirus, Norwalk agent, echo- and coxsackieviruses have all been shown to cause gastroenteritis. As few as 1 to 5 virus organisms can cause foodborne illness.

Methods of Isolation It is much easier to isolate viruses from fecal and vomit material than from foods. Hepatitis A virus and poliovirus have been studied extensively. However, it has been difficult to study the norovirus, snow mountain agent and other viruses

that cause enteric illnesses because it is yet impossible to culture them in a laboratory.

Methods of Control Foodservice workers must wash their hands, using a fingernail brush by the double hand wash method in order to assure that all fecal pathogens, which include viruses, are removed from their hands and fingernails. Only a safety-assured source of water should be used in food preparation and foodservice facilities.

Foodborne viruses can be inactivated by heat. Thorough cooking of food destroys viruses. The pasteurization of milk [161°F (72°C) for 15 seconds) is sufficient to destroy high levels of viruses. Ultraviolet light and hypochlorite (bleach) are effective against viruses on exposed surfaces, but do not reach viruses below the surface.

Seafood from contaminated waters often harbors fecal viruses. Seafood should be cooked well or it should be obtained from sources that certify safety of their seafood products. Any food can contain viruses.

It is important to remember that viruses do not grow on or in food, but can be transferred to another host (human or animal) by food or water. Viruses can survive refrigeration and freezing temperatures for months. They can be fairly resistant to heat. Peterson et al., (1978) reported that hepatitis A virus was not inactivated after thermal treatment of oysters at 140°F (60°C) for 19 minutes.

Foodborne Viruses of Significance Table 4-5 lists some of the enteric viruses of man that can be transmitted by food and water.

Table 4-5 Enteric Viruses of Man*

Virus Disease caused

Poliovirus Meningitis, paralysis, fever Hepatitis Type A Infectious hepatitis Norovirus Diarrhea, vomiting, fever Snow mountain agent Gastroenteritis

* Adapted from Gerba, 1988. Poliovirus has been transmitted in contaminated water and milk that was inadequately pasteurized. This virus is easily inactivated by heat. Poliovirus affects the central nervous system and can cause paralysis. A vaccine has been developed for this virus and the incidence of this disease has declined since the 1950s. However, when people are not immunized with the vaccine, the virus can cause a debilitating illness (e.g., when unvaccinated people drink raw milk from an infected cow).

Rotaviruses can cause life-threatening gastroenteritis in humans and animals. They can cause severe diarrhea and vomiting in children and adults. Rotaviruses are excreted in large numbers in the feces from infected persons, and have been isolated from water contaminated with sewage. Crops that are irrigated with raw or treated wastewater can transmit rotaviruses to humans, since rotaviruses can survive conventional sewage treatment. When vegetables such as

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radishes and lettuce are produced in this manner, they can carry rotaviruses.

Noroviruses (Norwalk virus) (caliciviruses) are small, round virus (.027 micrometers in diameter). Symptoms of the illness are nausea, vomiting, diarrhea, and abdominal cramps, which may last 2 to 3 days. Outbreaks of the illness have occurred in recreational camps, on cruise ships, in schools, and in nursing homes. Sources of these viruses have been attributed to contaminated water, ingestion of raw shellfish and other uncooked foods, and cake frosting handled in an unsanitary manner. Noroviruses are transmitted by the fecal-oral route and can be transferred by person to person contact. These viruses are resistant to the amount of chlorine (3.75 ppm) used in most water treatment facilities but can be inactivated by sanitizing solutions containing an adequate amount of chlorine.

Hepatitis A virus has been responsible for many documented foodborne illness outbreaks. Illness occurs when people eat contaminated food or drink contaminated water. The onset of symptoms is 10 to 50 days. Symptoms include jaundice, loss of appetite, and gastrointestinal disturbances. A lifetime immunity is developed as a result. However, hepatitis A virus affects the liver and serious long-term complications may result in some people. The virus is transmitted by human carriers, in contaminated food and water, and by shellfish taken from contaminated waters.

Other viruses. Snow mountain agent, a small round virus similar to norovirus, has been demonstrated to be the cause of both food and waterborne disease outbreaks. Astroviruses, calciviruses, and rotaviruses have been recognized as causing human gastroenteristis, and are undergoing study at this time.

References: Badawy, A.S., Gerba, C.P., and Kelley, L.M. 1985.

Development of a method for recovery of rotavirus from the surface of vegetables. J. Food Prot. 48(3): 261-264.

Cliver, D.O. 1988. Virus transmission via Foods. Food Technol. 42(4): 241-248.

Cliver, D.O. 1990. Foodborne Diseases. Academic Press, Inc. San Diego, CA.

Frazier, W.C. and Westhoff, D.C. 1988. Food Microbiology. Third edition. McGraw-Hill, New York, NY.

Gerba, C. P. 1988. Viral disease transmission by seafoods. Food Technol. 42(4): 99-103.



Peterson, D.A., Wolfe, L.G., Larkin, E.P., and Deinhardt, F.W. 1978. Thermal treatment and infectivity of hepatitis A virus in human feces. J. Med. Virology 2:201.

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Protozoa (single-celled animals with a nucleus)• Giardia lamblia

Control with filter or boiling• Toxoplasma gondii

Control with hand washing, food contactsurface sanitizing, heat >145ºF, 15 seconds

• Entamoeba histolyticaControl with heat >122ºF

Helminths• Trichinella spiralis• Taenia• Anisakis spp.• Control with:

Freezing according to government-specified temperatures and times

Heat >145ºF, 15 seconds

PARASITES

Parasites

Parasites in Foods Humans may consume infective forms of foodborne parasites when they eat raw or inadequately cooked food that contains these parasites, or drink water from an unsafe source. In this text, parasites of concern in food and water include protozoa and helminths (worms).

Protozoa Protozoa are single-celled animals that have a defined nucleus. They are larger than bacteria and can be seen with a microscope. Protozoa often feed on bacteria. Protozoa differ in size, shape, and their mobility by means of flagella, cilia, and pseudopodia.

There are many types of protozoa. They all have defined needs for growth, which include temperature, nutrients, atmosphere, and a supply of moisture. Some types of protozoa are beneficial, some are of no harm, and some can cause a wide variety of diseases. The protozoa that will be discussed in this text are those that can cause foodborne illnesses when these organisms are ingested in food and water.

Giardia lamblia is a flagellated protozoan. Giardia causes giardiasis in humans when it is ingested as a cyst (i.e., resting form of the living protozoa). Cysts form active forms of this protozoa (trophozoites) in the upper small intestine, which then attach to the intestinal lining. Here they consume mucous secretions and replicate by binary fission.

After an incubation period of about 15 days, infected persons experience a sudden onset of diarrhea, abdominal distension, gas, nausea, and loss of appetite. The acute stage lasts 3 to 4 days. During this time, Giardia can be passed in the feces.

Recent outbreaks of this illness have occurred as a result of drinking or using contaminated water. Foods can carry this organism if they become contaminated by a food handler, if they are irrigated with water that contains the organism, and if they are contaminated with an unsafe water supply during their preparation. Hikers in remote Rocky Mountain areas may contract this disease by drinking water from streams that have been contaminated with Giardia from wild animals such as beavers. Domesticated animals such as dogs, cats, and cattle may also be a source of this infection.

Giardia are thermally resistant. Suspect food and water should be heated thoroughly to boiling temperature [212°F (100°)]. As long as people carry this organism in their intestines, they can transmit this disease.

Toxoplasma gondii is a protozoan parasite that can be transmitted by fecal-oral contamination. Cats are the original hosts for these protozoa. The cats excrete oocysts (microscopic inactive forms of this protozoa) in their feces. Infectious sporozoites form within the oocysts 1 to 5 days after excretion. The oocysts containing the sporozoites are then transmitted to other animals in food (feeds) and water. When these oocysts reach the intestine, they break open, releasing 8 sporozoites. The sporozoites form active forms (tachyzoites and trophozoites) which multiply rapidly and spread to the rest of the body by way of blood and lymph. Eventually, these forms encyst themselves in the brain, heart muscle, other skeletal muscle, and liver. (These cysts are microscopic and can survive as long as the host lives.)

Farm animals (notably sheep, and pigs) can become infected by consuming feed and water contaminated by barn cats. When they are slaughtered to provide meat, the raw meat contains the cysts, which can then infect humans if eaten raw or not heated sufficiently to inactivate the various forms of this parasite. Fresh pork is the main meat source of Toxoplasma gondii in the United States. If cutting and grinding equipment is not thoroughly washed and sanitized, other raw meats such as ground beef can become contaminated. Cysts of this protozoa are also found in wild game meats such as elk, moose, and venison.

Clinical symptoms of the disease in humans are fever, muscle aches, headaches, loss of appetite and sore throat. (Other symptoms will appear depending upon the internal organ(s) involved.)

In pregnant women, these parasites can be carried by way of the placenta to fetal tissues. If fetuses are infected, miscarriages may occur.

If a woman acquires Toxoplasma gondii during pregnancy, there is a 20-to-50% probability that her fetus will be infected. Most infected infants show no obvious symptoms at birth, but will show signs of eye damage and mental retardation later in life. It is estimated that there are over 3,300 cases of congenital toxoplasmosis each year, resulting in 450 infant deaths. Other surviving infected children are mentally retarded as a result of this parasitic infection. Each year, it is estimated that over 2,000,000 people (excluding infants) in the U. S. are also affected by this parasite, resulting in 2 to 3 deaths.

This is a very serious infection. To prevent the spread of this disease, food handlers must wash their hands thoroughly with soap and water after handling meat. All cutting boards, utensils, and knives must be washed and sanitized thoroughly after coming in contact with raw meat, particularly raw pork. To insure the destruction of this parasite, meat of any type should be cooked until all parts of the meat reach a temperature of 145°F (62.8°C) for 15 seconds before it is consumed by humans or animals. Tasting raw meat should be avoided. Pregnant women should avoid contact with cats, soil, and raw meat. Vegetables should be washed thoroughly,

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because they may be contaminated with fecal material from cats.

Entamoeba histolytica causes amebiasis or amebic dysentery. Entamoeba histolytica is a large protozoan (50 micrometers). It exists in both an active form (trophozoite) and in an inactive form (cyst). Amebic dysentery occurs when food or water containing cysts of this protozoa are ingested. The cysts are not affected by the acidity and enzymes in the stomach and pass through the stomach to the intestine. Once in the intestine, the nuclei of cysts divide to form 8 new trophozoites (active forms). These active forms of this protozoa produce enzymes that enable it to invade the intestinal wall and produce lesions (sores). Infected persons experience severe abdominal pains and diarrhea, which may contain mucous and blood. This disease is sometimes confused with cancer of the colon and hemorrhagic colitis. These protozoa can penetrate the blood vessels of the bowel and be transported to the liver and lungs. Death may result due to the effect on these vital organs. Individuals are carriers as long as they pass cysts. People can be carriers for years.

Entamoeba histolytica is often responsible for traveler's diarrhea when visitors to tropical countries are exposed to communities with poor sanitation, poor personal hygiene, and a high incidence of carriers in the population. Amebiasis also occurs in northern climates and is epidemic among some native people living in the Arctic region.

To prevent the spread of this illness, there must be sanitary disposal of fecal material. Safe water supplies should be used to wash food during food preparation. Food should be grown under adequate sanitary conditions and should not be fertilized with animal or human fecal material. Food handlers must be taught to use proper hand washing procedures. This protozoa and its cysts are destroyed when food and water are heated above 122°F (50°C). Health organizations recommend boiling temperatures for suspect foods and water.

Helminths Helminths are parasitic worms that live at the expense of their hosts (humans, animals, fish, and birds). These worms are large enough to be seen without the aid of a microscope. However, a microscope is needed to detect their eggs or cysts. The parasitic worms of most concern in food include Trichinella spiralis, Taenia (tapeworms), and Anisakis spp.

Trichinella spiralis is a nematode (worm) that causes the illness or disease Trichinosis. Trichinosis develops when people consume raw or insufficiently cooked pork or other meat containing encysted larvae. The larvae are released into the intestinal tract during digestion and invade the mucous membranes of the intestine, where they develop into adults. Fertilized females produce numerous larvae, which travel through the circulatory system (blood and lymph) to skeletal muscle tissue where they again form cysts.

The incubation period for the first symptoms to develop varies from a day or two to as long as several weeks. Symptoms include nausea, vomiting, diarrhea, sweating, abdominal cramps, and loss of appetite. These symptoms may continue for days and are often confused with other foodborne illnesses. Later symptoms, which result from encystment of larvae in muscle include muscle soreness, spastic paralysis of muscles,

and swelling of eyelids, face, and hands. Death can occur with severe infections.

To prevent this disease in humans, methods of preventing the disease in hogs and using treatments that insure the destruction of this parasite in meat must be used. Hogs must be raised under the most sanitary conditions possible and should not be fed raw garbage. In order to insure the destruction of Trichinella spiralis, pork and game meat should be:

Cooked until every part of the meat reaches a temperature of 155°F (68°C) for 15 seconds; or 150°F (66°C) for 1 minute; or 145°F (63°C) for 3 minutes

•

• Quick frozen or stored at government-specified temperatures and times [e.g., -20°F (-28.9°C) for 6 to 12 days].

People should not consume raw or insufficiently heated game meats or pork, unless there is certification by the supplier that it is trichinella free.

Taenia are tapeworms and can cause disease in humans when larvae infested meat is eaten. People can be a host for both beef and hog tapeworms. The adult worm is a parasite in humans, while the larvae infest animal tissues. A cycle occurs when humans pass eggs or proglottids (segments of the tapeworm) in their feces. When people defecate or spread raw sewage in a crop area used to raise feed, the eggs and proglottids are passed on to the livestock. The eggs hatch within the animal host and develop larvae, which settle in the muscle. This encystment stage in livestock is called cysticercosis. When people consume raw or undercooked larva-infested meat, the larvae develop in the human intestinal tract into adulthood. Infestation of the human intestine with tapeworms is called taeniasis. The tapeworms produce eggs that are then passed in the feces, enabling the cycle to begin again, unless there is proper disposal of human fecal material.

Symptoms of the illness include: abdominal pain, nausea, weakness, weight loss, increased or decreased appetite, hunger pain, change in bowel habits, and nervousness. Humans are often unaware they carry this parasite until it is passed in fecal material. If these parasites become encysted in vital organs such as the liver, heart, lungs, eyes, and brain, their presence becomes life threatening.

The incidence of taeniasis has declined since the 1930s. However, there is still an estimated incidence of 1,000 cases in the U. S. each year, resulting in 10 deaths.

The USDA inspects carcasses for signs of cycticercosis and condemns carcasses that have extensive signs of tapeworm cysts. Carcasses with a very few number of lesions or cysts can be marketed, if the cysts are removed and the carcasses are exposed to freezing temperatures of 15°F (-9.4°C) or lower for 10 to 20 days. Carcasses with high infestations are condemned. Heating every part of the muscle to an end temperature of 140°F (60°C) is sufficient to destroy the larvae in meat.

Anisakis spp. are nematodes (worms) in fish. Consumption of raw or insufficiently processed fish may cause anisakiasis in humans. Natural hosts for adult worms are marine mammals such as dolphins, whales, and seals. Eggs excreted by these marine mammals are eaten by crustaceans. The crustaceans

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are eaten by fish or squid and the life cycle is completed when these are in turn eaten by sea mammals. People become infected by eating raw or undercooked seafood such as sushi. Anisakiasis is common in countries like Japan, the Netherlands and Scandinavia where people eat raw and underprocessed fish.

Signs and symptoms of the illness include irritation of the digestive tract and throat. Anisakine larvae can either remain free or become attached to the human digestive tract to cause irritation, inflammation, or ulceration. The larvae do not mature in people. They can be expelled by coughing or vomiting. Often, they must be removed surgically.

The larvae are destroyed if fish are heated to 140°F (60°C) or are frozen and stored at government-specified freezing temperatures and times. Cleaning (evisceration) of fish soon after catching them prevents the larvae from migrating from the intestinal tract to the muscle of the fish.

References: American Veterinary Medical Assoc. 1995. Zoonosis

Updates. 2nd edition. Am. Vet. Med. Assoc., Schaumberg, IL.

Anon. 1989. A case of Anisakiasis - Alberta. Canadian Weekly Report. Vol. 15(44): 221-224.

Chin, J., 2000. Control of Communicable Diseases in Man. 17th edition. The American Public Health Assoc., Washington, D.C.

Dubey, J.P. 1986. Toxoplasmosis. J. Am. Vet. Med. Assoc. 189 (2): 166-170.



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Histamine poisoning• Scombroid fish (tuna, snapper, grouper, amberjack,

mahi mahi)• Spoilage bacteria change histidine to histamine• Not heat denaturedParalytic shellfish poisoning• Shellfish ingest small dinoflagellates that provide toxins• Toxins are not inactivated by heatCiguatera poisoning• Dinoflagellates provide toxin that accumulates in fish

tissue• Toxin is not inactivated by heat

FISH AND SHELLFISH TOXINS AND POISONS

Fish and Shellfish Toxins

Types of Poisoning Marine fishery products may contain some of the most potent toxins known. These toxins are unaffected by cooking, and no antidotes or antitoxins exist to reduce their toxicity of some of these toxins. Poisonings through eating toxic fish and shellfish are significant causes of human illness. Outbreaks are usually due to three types of poisoning: histamine poisoning, paralytic shellfish poisoning, and ciguatera poisoning.

Histamine Poisoning Histamine poisoning is the second most frequently reported fishborne illness in the United States. Illness results from eating fish that have become toxic after undergoing some microbial decomposition, although signs of spoilage may not be evident. The fish belong to the Scombridae family and include tuna, snapper, grouper, amberjack, and mahi mahi.

Scombroid fish have high concentrations of the amino acid histidine in their tissues. When histidine is decarboxylated, the COO- group is removed from the molecule and histamine, the toxic agent, is formed. Fresh tuna has a histamine level of less than 20 mg per 100 grams. An excess of 100 milligrams per 100 grams histamine is reported in tuna that has undergone microbial decomposition. Morganella morganii and Klebsiella pneumoniae are the two types of bacteria most often associated with histamine formation in various scombroid fish.

The onset of symptoms is short, ranging from a few minutes to a few hours. Symptoms of scombroid (histamine) poisoning include: tingling and burning sensations around the mouth, flushing, a rash with itching, hypertension, rapid pulse, headache, dizziness, nausea, and diarrhea. If the condition is recognized quickly, the use of antihistamine therapy can be useful. With the exception of cheese, foods other than fish are rarely involved.

There is no immunity. The poisoning occurs throughout the world and is thought to be vastly under-reported.

An assay method for histamine is available and is applicable for routine use in a well-equipped laboratory. It is common commercial practice within the fisheries industry to inspect scombroid-type fish at point of receipt and in-plant at time of

evisceration for off-odors and other evidence of mishandling that could result in histamine formation. Routine examination for histamine is common even though decomposition is not evident.

After canning, the muscle tissue of some affected fish have a honeycombed decomposition pattern even when no visible changes are present in raw fish. Imported scombroid fish, usually tuna, are frequently inspected for evidence of deterioration and are analyzed for histamine content by the FDA. Canned albacore, skipjack, and yellow fin tuna with histamine levels of 20 mg or more per 100 grams are subject to regulatory action by FDA as being suspect of deterioration. The agency will consider regulatory action against any tuna found to contain between 10 and 20 mg of histamine per 100 grams when a second indication of decomposition is present. The FDA has established, on an interim basis, a level of 50 mg of histamine per 100 grams of tuna as the level of histamine in tuna that it considers a health hazard. Accordingly, this microbiological criteria with histamine as the designated contaminant is useful when applied, as indicated above, to prevent deteriorated fish as well as toxic fish from reaching the processor or consumer.

Paralytic Shellfish Poisoning Paralytic shellfish poisoning (PSP) is one of the most toxic forms of food poisoning. Certain species of dinoflagellates (flagellated protozoa), most notably Gonyaulax catenella and Gonyaulax tamarensis, produce saxitoxin, which is known to cause PSP. Ingestion of toxic shellfish causes acute toxicity in humans. Shellfish involved most frequently include mussels, clams, soft-shelled clams, butter clams, and occasionally, scallops.

Toxic shellfish may contain multiple toxins. Saxitoxin may represent only a part of the total toxicity. These newly discovered toxins are related to saxitoxin and their pharmacological action seems to be similar to that of saxitoxin.

In addition to gastrointestinal symptoms, PSP produces neurological symptoms including tingling lips within 15 minutes, profuse paralysis, and death in 2 to 24 hours. There is no antidote. Respiratory arrest causes death if the patient is not put on a respirator immediately. Major cardiac damage usually occurs if there is a heavy dose of toxin, even if the patient is given appropriate treatment. A field test for PSP is desperately needed.

There are medical records of over 1,650 cases of PSP (worldwide) that have resulted in at least 300 fatalities. Outbreaks, although infrequent, occur sporadically along the Atlantic and Pacific coasts of the United States.

Routine sampling and testing for toxins in shellfish obtained from wholesale or retail markets is not practiced, nor is it necessary. A microbiological criterion for PSP is applied when state authorities regularly assay representative samples of shellfish from growing areas. If toxin content reaches 80 micrograms per 100 grams of edible portion of raw shellfish meat, the area is closed to harvesting of the species involved. These actions and other preventive measures are undertaken in accordance with the National Shellfish Sanitation Program (NSSP), a federal-state-industry cooperative program. Cases

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of PSP have resulted from shellfish taken from closed fishing areas where fishing was prohibited.

Note, The NSSP is not funded by the national government, but by state governments. Sometimes state governments do not fund these control programs in their states. Therefore, a seafood buyer must get the supplier to certify PSP safety.

Ciguatera Poisoning Ciguatera poisoning is one of the largest public health problems related to poisoning from ingestion of fish. Ciguatoxin has been known since the time of the Conquistadors in the 1600s when affected sailors continued to have asthenia (loss of body strength) and arthralgia (pain in the joints along the nerves) for years after consumption.

Ciguatoxin poisoning occurs throughout the Caribbean and tropical Pacific regions, where outbreaks have been reported by both residents and tourists. From 1983 to 1992 in the United States, 129 outbreaks of ciguatera poisoning involving 508 persons were reported to the CDC. No ciguatera-related deaths were reported. Most outbreaks were reported from Hawaii and Florida, although outbreaks and sporadic cases occurred in California, New York, and Illinois. (The case in Illinois was due to imported fish.)

The toxin is synthesized by the dinoflagellate Gambierdiscus toxicus, and possibly by certain other dinoflagellate species. Fish may feed on these organisms and accumulate the toxin in their tissues. As the toxin passes through the fish food chain, it increases (i.e., large carnivores tend to be more toxic than herbivores and small carnivores). The fish are seemingly unaffected toxin accumulation. Large, old barracuda carry great quantities of toxin in their flesh. Fish found in the Pacific Ocean and throughout the Caribbean are often sources of ciguatoxin.

Four to eight hours may elapse between ingestion of the poison and the onset of symptoms, which include weakness and abnormal sensory phenomena. Beyond the gastrointestinal upset, the involvement of the cardiovascular and neurological systems is even more serious. Blood pressure drops and tachycardia (rapid heartbeat) develops; numbness and the reversal of hot and cold sensations occur. The infective dose is less than l mg of toxin. More than 10,000 cases occur annually, worldwide.

The factors that trigger the buildup of toxic concentrations of the toxin of G. toxicus and possibly those of other dinoflagellate species are not clear. Fish toxins, other than ciguatoxin, are not well defined and assay methods for them are neither precise nor specific. Because of the lack of sufficient knowledge in these areas, there are no federal or state surveillance programs for preventing the occurrence of ciguatoxin poisoning. Supplier certification is the only safety control available. The toxin is heat stable and remains in fish after it is cooked.

Human ciguatera poisoning can occur after consumption of a wide variety of coral reef fish, such as barracuda, grouper, red snapper, amberjack, surgeonfish, and sea bass. Ciguatoxin and related toxins are derived from dinoflagellates, which herbivorous fish consume while foraging through the macro-algae. Humans ingest the toxin by consuming either herbivorous fish or carnivorous fish that have eaten the

contaminated herbivores. Larger, more predacious reef fish are more likely to be toxic. Since the toxin is heat-stable, cooking does not make the fish safe to eat.

As the domestic and imported fish industry expands its market, the diagnosis of this "tropical" disease must be considered even in areas to which coral-reef fish are not native. Ciguatera fish poisoning can be diagnosed by the characteristic combination of gastrointestinal and neurologic symptoms in a person who ate a suspect fish. The diagnosis can be supported by detection of ciguatoxin in the implicated fish.

Hawaii now uses a "stick test" immunoassay to detect ciguatoxin in fish. The test is sensitive, specific, inexpensive, and easy to use in the field. In Hawaii, if an outbreak-related fish tests positive for ciguatoxin, the reef area of catch is closed to discourage further fishing in that area. In Miami, Florida, because barracuda have been frequently associated with ciguatera poisoning, a city ordinance bans the sale of barracuda.

OUTBREAK EXAMPLE. The following outbreak example appeared in MMWR 47(33) 692, 1998.

Ciguatera Fish Poisoning – Texas. On October 21, 1997, the Southeast Texas Poison Center was contacted by a local physician requesting information about treatment for crew members of a Norwegian cargo ship docked in Freeport, Texas, who were ill with nausea, vomiting, diarrhea, and muscle weakness.

Gastrointestinal illness developed after the crew members ate fish on October 12. Of 23 crew members interviewed, 17 (74%) reported the following symptoms: diarrhea (17 [100%]), abdominal cramps (14 [82%]), nausea (13 [76%]), and vomiting (13 [76%]). Symptoms occurred within 2 to 16 hours after eating fish. All ill crew members also experienced neurologic symptoms characteristic of ciguatera poisoning. These symptoms included: muscle weakness and pain, numbness or itching of the mouth, itching of the hands and feet, temperature sensation reversal, dizziness, and aching or loose feeling teeth. Seventeen crew members ate the barrocuda and all became ill. Although crew members also ate red snapper and grouper at the same meal, neither of these fish were linked epidemiologically with illness.

Investigators found samples of the leftover barracuda that was eaten, in cold storage on the ship. These samples tested positive for ciguatoxin.

References: Ahmed, F. 1991. Seafood Safety. National Academy Press.

Washington, D.C. CDC 1998. Ciguatera fish poisoning - Texas 1997. MMWR

47 (23) 692-694. Jay, J.M. 2000. Modern Food Microbiology. 6th edition.

Chapman & Hall Inc., New York, NY. Mossel, D.A.A., Corry, J. E., Struijk, C. B., and Baird, R.


Taylor, S.L. 1988. Marine toxins of microbial origin. Food Technol. 42(3):94-98.

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GROWTH OF BACTERIA IN FOOD BASED ON FDA FOOD CODE HOLDING / STORAGE RECOMMENDATIONS

The Multiplication of Pathogenic Bacteria

and Factors Controlling Multiplication Bacterial Multiplication Controls If favorable environmental conditions exist, bacterial multiplication occurs. When dormant bacteria are transferred to a nutritious medium such as warm turkey broth, there is a short period of adjustment known as the "lag phase," before they begin to multiply. The lower the temperature, the more unfavorable the chemistry of the food, the longer the lag period. At optimum temperatures [e.g., 95°F (35°C) the lag phase is quite short, 2 hours. During the lag phase, the dormant cells warm up and soak up nutrients. The metabolic cycle inside the cells begins to function at an optimum rate.

After some hours or days, depending on temperature, atmosphere, water, and pH, the vegetative cells begin to multiply logarithmically: 2 become 4, then 8, then 16, etc. Table 4-6 shows that 5 generations of bacteria only permit a multiplication of 1 to 32.

Table 4-6 Logarithmic Bacterial Population Multiplication

Generation Number of

Bacteria 1 2 2 4 3 8 4 16 5 32 6 64 7 128 8 256 9 512

10 1,024 Allowing the first 5 generations of microorganisms to be produced usually does not create a hazard in the food or food product. Allowing most of the vegetative infective pathogens to reach a population of greater than 1,000 must always be considered hazardous. Note that this is not true for Staphylococcus aureus, Bacillus cereus, Clostridium perfringens and Clostridium botulinum type E, which must

reach a population of 105 to 106 microorganisms per gram of food. A 10-generation multiplication is probably safe.

The population of pathogens in food should be low enough to allow time for refrigerated storage before the number of pathogenic bacteria in the product becomes hazardous. Refrigerator storage does not inhibit the multiplication of all pathogenic bacteria. Some pathogenic bacteria are capable of multiplying at refrigeration temperatures between 30 to 40°F (-1.1 to 4.4°C) (Hauschild, 1989; Hudson et al., 1994; van Netten et al., 1990).

Eventually, when a bacterial population is around 10,000,000 to 50,000,000 / gram or slightly higher, waste concentration becomes high and the growth nutrients are so scarce that the microorganisms stop multiplying and enter the stationary phase. A critical question is: "What type of pathogen multiplied?" If it is a pathogen whose waste products are toxic, then further processing such as reheating to 165°F (73.9°C) will not make the food safe. Staphylococcus aureus, C. botulinum, and B. cereus can all produce this type of toxin. Therefore, pathogenic growth must be limited to levels that are not harmful (less than 10 multiplications). The stationary phase is followed by the death phase when vegetative cells decrease in numbers and internal bacterial enzymes dissolve the non-multiplying cells. However, if toxins have been produced, they will remain in the surrounding media or food.

For multiplication, bacteria need the proper amount of oxygen or lack of oxygen depending on whether they are aerobic (require oxygen) or anaerobic (do not require oxygen). They also require proper temperature, adequate nutrients, free water, time, and a favorable acid or base pH. Any imbalance of these factors can reduce or stop bacterial multiplication.

Bacteria reproduce by cell division. That is, they multiply by increasing in number, not by growing in size. They can double in approximately 8 to 30 minutes at optimum temperatures of 95 to 115°F (35.0 to 46.1°C). This multiplication occurs during inadequate hot holding, or slow cooling in a refrigerator. To be safe, food must be held at temperatures greater than 130°F (54.4°C) or less than 30°F (-1.1°C).

Snyder (1997) has compiled a recommended set of times and temperatures for holding food. The recommended times for holding food are shown in Table 4-7. The numbers are based on the FDA Food Code, which allows 7 days at 41°F (5°C), 4 days at 45°F (7.2°C), and 4 hours if food is held between 46 to 139°F (7.8 to 59.4°C). The temperature for most rapid growth during the 4 hours is about 112°F (44.4°C). Ratkowsky et al. (1983), have developed an equation that can be used to predict growth at temperatures in between given anchor points. By using the FDA Food Code values and anchoring the ends of the growth line at about 30°F (-1.1°C) and 126°F (52.2°C) values for Table 4-7 can be predicted. These data can then be used to calculate the time for 1 generation to multiply to 10 generations over the entire growth range.

How can this be used? The Microbiological Multiplication Calculator, on the following page, is a work sheet that allows one to analyze a process with fluctuating temperatures and to use this information to judge if the process reached the 10-generation safety limit derived from FDA-recommended

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holding times of 7 days at 41°F (5°C), 4 days at 45°F (7.2°C), or 4 hours at 112°F (44.4°C). The Quality Assurance person simply logs the food handling times and temperatures. Once the process data is logged, the equivalent growth can be calculated for each process step by multiplying the time at each temperature by the multiplication rate and entering it on the column titled, Accumulated Multiplication. The food should be cooked or eaten before there have been 10 multiplications.

The values of 41°F (5°C), 4 days at 45°F (7.2°C), and 4 hours at 112°F (44.4°C) derived from FDA Food Code recommendations are all very conservative. At temperatures below about 70°F (21.1°C), spoilage microorganisms multiply more rapidly than pathogens.

Cooling The lag is also important during cooling. Spores of B. cereus, C. botulinum, and C. perfringens are activated above 140°F (60°C). (Normal activation is 180°F (82.2°C) for 15 minutes.) When food cools to below 127.5°F (53°C), the spores begin to germinate and grow out as vegetative cells that begin to metabolize and multiply. The FDA Food Code recommends cooling potentially hazardous food to 41°F (5°C) within 6 hours [§3-501.14: from 135 to 70°F (57.2 to 21°C) within 2 hours followed by cooling to 41°F (5°C) or below within a total time of 6 hours]. To accomplish this a $20,000 blast chill refrigerator must be used for cooling food. USDA Guidelines recommend cooling food, within 90 minutes after cooking, from 120 to 55°F (48.9 to 12.8ºC) within 6 hours, followed by further cooling to 40°F (4.4ºC) (no time limit) before boxing.

References: Hauschild, A.H.W. 1989. Clostridium botulinum. In

Foodborne Bacterial Pathogens. Doyle, M.P., ed., Marcel Dekker, Inc., New York, NY.


Hudson, J. A., S. J. Mott , and N. Penney. 1994. Growth of Listeria monocytogenes, Aeromonas hydrophila, Yersinia enterocolitica on vacuum and saturated carbon dioxide controlled atmosphere-packaged sliced roast beef. J. Food Prot. 57 (3) 204-208.

Ratkowsky, D. A., R. K. Lowry, T. A. McMeekin, A. N. Stokes, and R. E. Chandler. 1983. Model for bacterial culture growth rate throughout the entire biokinetic temperature range. J. Bacteriol. 154(3):1222-1226.

Snyder, O. P. 1997. Updated Guidelines for Use of Time and Temperature Specifications for Holding and Storing Food in Retail Food Operations. Dairy Food Environ. Sanitation. 18: 574-579.

van Netten, P., van de Moosdijk, A., van Hoensel, P., Mossel, D.A.A., and Perales, I. 1990. Psychrotrophic strains of Bacillus cereus producing enterotoxin. J. Appl. Microbiol. 69: 73-79.

Table 4-7 Maximum Holding Times at Specified Temperatures

°F

°C

1 Multiplication of Pathogens

SAFETY LIMIT*

10 Multiplications

of Pathogens <30 <-1.1 Safe Safe

30 -1.1 297.14 hours 123.8 days 35 1.7 46.34 hours 19.3 days 40 4.4 17.99 hours 7.5 days 41 5.0 15.55 hours 6.5 days 45 7.2 9.49 hours 4.0 days 50 10.0 5.85 hours 2.4 days 55 12.8 3.96 hours 1.7 days 60 15.6 2.86 hours 1.2 days 65 18.3 2.16 hours 21.6 hours 70 21.1 1.69 hours 16.9 hours 75 23.9 1.36 hours 13.6 hours 80 26.7 1.12 hours 11.2 hours 85 29.4 0.93 hours 9.3 hours 90 32.2 0.79 hours 7.9 hours 95 35.0 0.68 hours 6.8 hours

100 37.8 0.59 hours 5.9 hours 105 40.6 0.52 hours 5.2 hours 110 43.3 0.47 hours 4.7 hours 115 46.1 0.46 hours 4.6 hours 120 48.9 0.56 hours 5.6 hours 125 51.7 3.10 hours 31.0 hours

* Food should be cooked, eaten or discarded before there

have been 10 multiplications.

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MICROBIOLOGICAL MULTIPLICATION CALCULATOR By_________________________________________________________________ Date _________________ Process ______________________________________________ Task _______________________________

Description

Temp.

(oF)

Time (hr.)

Multipli- cation

rate / hr.

Multipli-

cation

Accumulated multipli-

cation

Table of Calculated Rates at Specified Temperatures

Temp.

(oF) Multiplic. rate / hr.

Temp. (oF)

Multiplic. rate / hr.

<30 Safe 82 0.96530 0.003 83 1.000 35 0.022 84 1.036 40 0.056 85 1.073 41 0.064 86 1.110 42 0.074 87 1.148 43 0.084 88 1.186 44 0.094 89 1.225 45 0.105 90 1.265 46 0.117 91 1.305 47 0.130 92 1.346 48 0.143 93 1.387 49 0.157 94 1.429 50 0.171 95 1.472 51 0.186 96 1.515 52 0.202 97 1.558 53 0.218 98 1.602 54 0.235 99 1.647 55 0.252 100 1.692 56 0.271 101 1.737 57 0.289 102 1.782 58 0.309 103 1.827 59 0.329 104 1.872 60 0.350 105 1.917 61 0.371 105 1.961 62 0.393 107 2.004 63 0.416 108 2.045 64 0.439 109 2.083 65 0.463 110 2.119 66 0.487 111 2.149 67 0.512 112 2.174 68 0.538 113 2.190 69 0.565 114 2.196 70 0.592 115 2.188 71 0.619 116 2.163 72 0.648 117 2.115 73 0.676 118 2.038 74 0.706 119 1.927 75 0.736 120 1.775 76 0.767 121 1.573 77 0.798 122 1.319 78 0.831 123 1.013 79 0.863 124 0.668 80 0.897 125 0.323 81 0.931 126 0.058

>127.5 Safe

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1/20/2005 1901(4a) 131326

DESTRUCTION OF SALMONELLA SPP. IN FOOD

DEATH CONTROLSTime and temperatureNutrients and acidsWater activity

6.7 sec.5.2 sec.160 (71.1)

21 sec.16 sec.155 (68.3)

67.sec.52 sec.150 (65.6)

3.5 min.2.7 min.145 (62.8)

11.2 min.8.7 min.140 (60.0)

35 min.27 min.135 (57.2)

112 min.86 min.130 (54.4)

6.5D Roast beef

(3,160,000:1)

5D Hamburger (100,000:1)

Temp.ºF (ºC)

DESTRUCTION OF SALMONELLA IN FOOD

Destruction of Foodborne Disease Bacteria

Destruction of Bacteria Favorable environmental conditions of temperature, nutrient, pH, aw and oxidation-reduction conditions over a period of time promote the multiplication of microorganisms. By altering these conditions, the multiplication of microorganisms can be controlled and/or their destruction can be achieved.

Time and Temperature Time and temperature can be manipulated in order to destroy bacteria. Just as growth is logarithmic, destruction is also logarithmic. The higher the temperature, the shorter the time required to accomplish destruction of bacterial cells and spores. The figure shows data that are typical of Salmonella spp. Salmonella spp. is a common foodborne illness-producing organism and hence, is suitable to use to develop safety standards. One thousand Salmonella spp. per gram can be reduced to 1 per 100 grams of food (a 5D or 5 log reduction) in 8.7 minutes at 140°F. (A 1D reduction is 1 log reduction.) At a temperature of 150°F, the process would take 52 seconds. Only 5.2 seconds would be needed to accomplish the same reduction at 160°F. Note that for each 10°F increase in temperature, the salmonellae die 10 times faster. Time and temperature control is far more important in pasteurization of food than in cold holding and refrigeration; 3ºF error in measuring the coldest spot in a food item can mean the survival of twice as many organisms. Precise cooking is essential if there is to be safety without overcooking. A tip-sensitive, electronic thermometer must be used. Note that the food code calls for a 6.5D reduction of Salmonella for roast beef. Of course, hamburger is more contaminated than roast beef, but the roast beef requirement, which was established in 1978, simply has not been changed by the government.

At 140ºF food center temperature, which is a rare hamburger, it is virtually impossible to hold food for 8.7 minutes to get a 5D pasteurization on a fast-cooking device such as a grill, broiler, or griddle without the temperature increasing. Note, the FDA code allows pasteurization at 145ºF, 3 minutes; 150ºF, 1 minute; and 155ºF, 15 seconds. The conclusion is that rare meat, unless the supplier certifies it as vegetative-pathogen free, cannot be made safe except in slow cooking, such as oven roasting of beef, pork, lamb, etc. In ordinary grill / griddle cooking, the outside of the food is well above 150ºF, by the time the food is taken off the grill at 150ºF

center temperature. The food temperature will tend to coast up, so it will be more than 1 minute to 150ºF before the grilled item starts to cool, and a 5D (100,000-to-1) kill will have been achieved. If the hamburger is ground from fresh product, not aged beef, and if there are no additives such as soy, the color will be a pleasing, medium pink at 150ºF center temperature. When meat is heated to 160ºF center temperature, there will be little red color left in fresh beef, pork, lamb, chicken, etc., and these items, which are medium well, are overly safe. Cooks have been taught to cook meat until the red color is gone, or above 160ºF, not because of safety, but rather, it was assumed that no one had a proper thermometer to measure temperature, and color was an adequate control. The USDA now says that one will never cook by color, because color cannot be trusted to indicate food temperature. One must cook with a tip-sensitive, electronic thermometer.

The addition of acids such as lemon juice, vinegar, and wine to food products not only adds flavor to the product but also lowers the pH of the food, which slows down or inhibit bacterial growth and aid in destruction of bacteria when combined with heat. It will also turn meat brown at lower cooking temperature. If it is aged and acidic, meat is brown at 150ºF. Meat with 15% textured vegetable protein is brown at 140ºF. On the other hand, if meat is cooked with onions and celery, high in nitrate, the color of meat becomes the color of cured meat (e.g., ham) and does not turn completely brown, even when a temperature of 180ºF is reached.

Nutrients and Acids (pH) When the supply of nutrients is low or not optimum, the multiplication of microorganisms is slow and decline in numbers occurs.

The incorporation of food components that lower the pH of food products contributes to the destruction of microorganisms. The pH of some foods (e.g., lemon juice, wine, vinegar) is quite acid. The presence of organic acids and alcohol in these foods make heat destruction more effective. When the pH of food is low (quite acid), bacterial destruction at a specific temperature is much faster.

Water Activity Microorganisms require moisture to multiply. Multiplication is restricted in an environment where water is not available or bound by other food components such as salt, sugar, and glycerol. Foods high in moisture, such as fresh fruits and vegetables, meat, fish, poultry, etc., permit rapid multiplication of microorganisms. The water in the structural system of these foods is available for the metabolic functions of microorganisms. When water is removed to a sufficiently low level (e.g., cereals, dried fruits and vegetables), the multiplication of microorganisms is suppressed. Hence, these foods are shelf stable at room temperature until they absorb sufficient amounts of water from the atmosphere, at which time the multiplication of microorganisms will begin.

Although the multiplication of microorganisms is suppressed as the aw of a food system is lowered, some microorganisms survive. It is much harder to inactivate these surviving microorganisms in low water activity foods. Higher temperatures for longer periods of time are required to ensure destruction. A practical application of this knowledge is to add sugar or salt, which lowers water activity to a food

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product such as egg custard only after it has reached the pasteurization temperature of 165°F (73.9°C), and the milk, eggs, meat, etc. are pasteurized.

Survival: Vegetative Cells vs. Spores Vegetative cells are quite susceptible to thermal destruction and are reduced to a safe level at the times and temperatures shown in the slide at the beginning of this section (#1326). Spores, which are inactive forms of some microorganisms, require much higher temperatures for inactivation. For example, a temperature of 250°F (121°C) for 15 seconds in the middle of the product is required to produce a 1 log population reduction of Clostridium botulinum type A spores. The minimum sterilization standard for canned food is to reduce C. botulinum spores by 12D, or 1,000,000,000,000 to 1. Spores of some spoilage microorganisms are even more heat resistant, so, canned food is often processed at 250ºF (121.1ºC) for 9 to 12 minutes.

Spores are present in food, and they can survive most cooking processes. An exception is the spores of C. botulinum Type E, commonly found in fish. At 180°F (82.2°C), 0.8 minutes was required for a 1 log cycle reduction of C. botulinum Type E spores in evaporated milk, while 6.6 minutes was required to reduce the number of spores in tuna packed in oil (Simunovic et. al., 1985). The longer time required for the destruction of spores in oil is an illustration of the protective effect of fat in food products.

Freezing While freezing is not a reliable method for destroying bacteria, viruses, yeasts, and molds, it is reliable for the inactivation of parasites. The FDA and USDA have specified temperatures at specific times, depending on the type of parasite and the size of the product. The colder the temperature, the more rapid the destruction.


4th ed. McGraw-Hill, New York, NY. International Commission of Microbiological Specifications

for Foods. 1996. Microbial Ecology of Foods. V ol.5. Microorganisms in Food. Microbiological Specifications of Food Pathogens. Blackie Academic & Professional, New York, NY.



Simunovic, J., Oblinger, J.L. and Adams, J.P. 1985. Potential for growth of nonproteolytic types of Clostridium botulinum in pasteurized restructured meat products: A review. J. Food Prot. 48 (3): 265-276.

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1/20/2005 1901(4a) 141283

Food Infection: Illness occurs as a result of consuming food containing living pathogenic microorganisms that then multiply in the body [e.g., Salmonella spp., hepatitis A virus, trichinae].

Food Intoxication: Illness caused by consuming food containing toxins produced by bacteria when they multiply in food [e.g., Staphylococcus aureus, Clostridium botulinum, Bacillus cereus].

Food Poisoning: Illness resulting from eating substance or compound that the body cannot detoxify [e.g., some mushrooms, cleaning and sanitizing chemicals, MSG, sulfites, metal (lead) poisoning]. Normal cooking has no effect on poisons and will not make poisonous food safe.

TYPES OF ILLNESS

Types of Foodborne Illness – Infection,

Intoxication, and Poisoning Types of Illness Foodborne diseases or illnesses are reactions of the body to consumption of foods containing sufficient quantities of pathogenic bacteria and/or their by-products or poisonous substances. The diseases (illnesses) are classified either as infections, intoxications, or poisonings. When foodborne illnesses are classified according to these three causes, control procedures can be applied for each cause.

Infection A food infection occurs when living pathogenic bacteria are consumed in sufficient numbers, survive digestion, and multiply or sporulate in the body.

Two types of foodborne infections are known. One type results when the intestinal mucosa is penetrated and the infecting organism multiplies therein or passes to other tissues where it multiplies or lodges. For example, hepatitis A virus, is absorbed through the intestinal wall, assimilated in the blood stream, and carried to the liver. It lodges in liver cells and multiplies. The second type of infection results when enterotoxins are released as the infecting organism multiplies, sporulates, or lyses (fragments or breaks apart) in the intestinal tract.

Infections in humans and animals result in varied symptoms, and their manifestations differ in severity. Organisms can colonize on the skin of the body, the intestinal tract, the mucosa, and the body tissues without producing identifiable evidence of a host reaction. An example of this is Staphylococcus aureus, which is a common resident in the noses of healthy people. Individuals with no symptoms nor gross signs of infection can have infecting microorganisms in their feces and urine and on their skin. When infections develop, symptoms can range from mild to severe, and are identified as clinical diseases or illnesses.

Disease or illness is the host response to the pathogenicity and virulence of an organism. Pathogenicity is the capacity of an agent to cause disease in an infected host and to produce severe illness, depending on virulence. Infected persons or animals are potential sources of infections. Carriers are persons who are infected and show no signs or symptoms of illness. A person can be a carrier in a stage of infection that

either precedes or follows clinical signs or symptoms, as well as during the clinical stages of the illness. Both hepatitis A virus and Salmonella spp. can be transmitted by carriers.

Control of Infective Microorganisms Those pathogens that cause infection are inactivated by heat and are normally destroyed, if food is properly cooked. However, they are dangerous when levels causing illness in unheated food or recontaminated cooked food are consumed. Adequate heating of foods, cleanliness and sanitation of facilities, appropriate personal hygiene by all foodservice workers, and progressive batch cooking of food are methods of controlling multiplication of these pathogens in food. Careful hand washing is extremely important. Human feces can contain 108 pathogens per gram. If they are not reduced to a very low number (1 to 10 per gram), through sufficient hand washing, they can introduce enough infective microorganisms into a bowl of food, punch, or salad to cause illness in hundreds of people.

Pathogens that cause illness through infection and that can be inactivated by heat include:

Bacteria Brucella Listeria monocytogenes Salmonella spp. Yersinia enterocolitica Shigella spp. Campylobacter jejuni Vibrio spp. Escherichia coli Viruses Hepatitis A virus Noroviruses Parasites Taenia saginata Entamoeba histolytica Trichinella spiralis Toxoplasma gondii Giarda lamblia F

ish tapeworms, round worms, and flukes

Intoxication Bacterial toxins. An intoxication is caused by the ingestion of metabolic by-products, or toxins, which are formed and excreted by certain microorganisms when they multiply in foods. The onset of symptoms usually occurs within a short period of time (often less than 2 hours) after eating food containing the toxin.

A fairly high bacterial population (i.e., 105 to 106 per gram) is required to produce toxin at illness-causing levels. The time required for toxin producing microorganisms to multiply and produce toxin in foods is usually more than 8 hours, even at temperatures above 70°F (21.1°C). Some toxins are altered by heat, and if products containing these toxins are heated for sufficient periods of time, the toxin is inactivated. (Toxins produced by Clostridium botulinum are destroyed when products are heated to 185°F (85°C) for 5 minutes.) Some toxins are quite resistant to heat. (Type A toxin produced by Staphylococcus aureus retains its toxigenicity at boiling temperatures for more than 25 minutes.)

Some pathogens form toxins within the intestinal tract. For example, Clostridium perfringens, a spore-forming pathogen, produces a toxin when vegetative cells form spores in the intestine.

Some toxin-producing pathogens are also spore-formers (e.g., C. botulinum and B. cereus). These pathogens are dangerous because the heat-resistant spores are difficult to destroy.

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Control of Toxin-Producing Microorganisms The most effective control for toxin-producing microorganisms is preparing, storing, holding, and serving food at temperatures and conditions that prevent their growth in foods.

Pathogens that produce toxic by-products in foods include:

Non-spore forming: Staphylococcus aureus

Spore forming: Clostridium botulinum, Bacillus cereus

Mold toxins. Mycotoxins (toxic substances produced by molds) represent a human health hazard. The full extent of this hazard is not known at this time. Some mycotoxins have an effect on liver and kidney function and some affect the central nervous system. Aflatoxin is a mycotoxin produced by the growth of Aspergillus flavus in grains, nuts, and legumes of high moisture content. Aflatoxin is known to cause cancer of the liver in animals.

Mycotoxin control. To understand the effect of mycotoxins on public health, methods have been developed to quantify their concentration in human diets. Methods of detecting the presence of mycotoxins in food have been developed and acceptable limits have been established for grains, nuts (e.g., peanut butter) and legumes. Harvesting, processing, and storage conditions influencing mycotoxin production have been examined. Better methods are being developed to reduce the incidence of this hazard.

Molds that produce mycotoxins in food include:

Aspergillus flavus Byssochlamys nivea Fusarium spp. Poisoning Food poisoning. Food poisoning is intoxication that results from the consumption of a substance that the liver and other organs cannot detoxify or eliminate from the body. Usually, but not always, there is a rapid onset of unfavorable symptoms. Examples include:

An excess amount of monosodium glutamate in food. • •

• •

•

• • •

Accidental addition of cleaning and sanitizing chemicals to food. Consumption of poisonous mushrooms. Heavy metal poisoning resulting from acid foods (e.g., salad dressing, fruit juices, and wine) leaching out cadmium, copper, and lead from some pottery and metal containers. Copper leached from copper water lines by carbon dioxide backflow valves on carbonated beverage vending machines. Scombroid and ciguatera fish poisoning. Mistaken use of nitrates for salt in salt shakers. Solanine formed when potatoes are exposed to sunlight.

In 1981, some 25 people suffered mushroom poisoning resulting in 3 fatalities. Four cases of MSG poisoning were reported that year. From 1983 to 1987 an average of 250 documented food poisoning cases per year were attributed to mushrooms, heavy metals, and other chemicals, scrombotoxin, and ciguatoxin.

Control. Once there is a toxic compound or poison in a food, there is nothing a foodservice operator can do. The only control is to purchase foods that the supplier certifies are safe, teach employees the importance of using the proper amount of food chemicals, and separate concentrated chemicals such as sanitizers, insecticides, and rodenticides in locked storage areas.

Poisons that may be present in food as a result of intentional or unintentional contamination include:

Cleaning compounds Sanitizers Nitrates, nitrites Mushrooms Heavy metals Monosodium glutamate Sulfites Ciguatoxin H

istamines Paralytic shellfish toxin

Summary Bacterial pathogens that can cause illness by infection or by production of toxins must always be assumed to be present in food. Spores of Clostridium botulinum, Bacillus cereus, and Clostridium perfringens survive most cooking procedures. Other pathogens such as Salmonella and Staphylococcus aureus may enter food through cross-contamination after it is cooked.

Cooking or reheating food will destroy vegetative cells of pathogenic bacteria but probably will not inactivate spores and toxins produced by some pathogenic microorganisms. Cooking or reheating foods cannot be relied upon to make foods safe.


4th ed. McGraw-Hill, New York, NY. Jay, J. M. 2000. Modern Food Microbiology. 6th ed.



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1/20/2005 1901(4a) 15679

FOODBORNE ILLNESS SITES IN THE BODY

Human Foodborne Illness – Sites,

Incubation, and Symptoms Foodborne Illness Symptoms Symptoms of foodborne illness can affect many different sites in the body. These include vital organs such as the liver, kidney, heart, and lungs; the vascular system; the central nervous system; the skeletal system; and excretory system. Important symptoms and causes of foodborne illnesses are listed in Table 4-8. Most people think of foodborne illnesses as having only short-term (i.e., a few hours to a few days) effects. This is not always true. Some foodborne illnesses can be life threatening and can have long-term effects.

Botulism Onset. Symptoms of botulism usually develop within 12 to 36 hours after ingestion of food containing botulinum toxin. In extreme cases, symptoms occur within 2 hours or after 14 days.

The severity of the illness is dependent upon amount of toxin ingested. The toxin of Clostridium botulinum is extremely lethal and only small amounts are necessary to cause illness and death if undiagnosed and untreated. The toxin is absorbed into the bloodstream through the small intestine. It then circulates throughout the body and is responsible for neurological impairment when it binds to the neuromuscular nerve junctures. The result is blockage of neurotransmitters, as a result vital organs (heart, lungs, intestinal tract) stop functioning.

Symptoms. Before neurological symptoms appear, gastrointestinal symptoms such as nausea, vomiting, and diarrhea may often develop, particularly in Type E botulism.

Weakness, lassitude, dizziness, and vertigo often develop early. Blurred vision, diplopia, dilated and fixed pupils, and impaired reflection of light appear very frequently. Difficulty in speech and in swallowing, severe dryness of the mouth, tongue, and throat are also noted. Abdominal fullness and pain are often seen, particularly in Type E cases. Constipation is severe. Muscle weakness occurs in the soft palate, tongue, diaphragm, neck, and extremities causing difficulty in walking and decreased grip. The respiratory muscles and diaphragm may become paralyzed.

The cause of death is a paralysis of the respiratory muscles. Botulism has a high death rate in the United States. Approximately 65% of afflicted persons die. This high death rate is the reason botulism is much feared in spite of the fact that it does not occur often. Complete recovery of the nonfatal cases is very slow and may extend over several months.

Clinical diagnosis of botulism is confirmed by detection of the toxin in the incriminated foodstuff or in patient's specimens (i.e., serum, vomit, feces). Toxin in the blood serum can usually be detected for a few days following ingestion of botulinum toxin and sometimes for up to 25 days.

The illness may be treated by administering an antitoxin specific for the particular type of toxin involved. Despite the availability of antitoxins, botulism therapy is still not satisfactory due to the lag times between the ingestion of the food, the appearance of symptoms, the diagnosis, and the procurement of the specific antitoxin. The general availability of the specific antitoxins is limited. Many hospitals do not stock the antitoxins because of the rarity of botulism incidents.

Toxic dose. As few as 10 spores, if allowed to out-grow and form vegetative cells in improperly processed, packaged, and stored food products having low oxygen availability, can produce sufficient toxin to cause a serious, even fatal, case of botulism. An inoculum of 104 to 105 cells per gram of food has been shown to be sufficient to produce sufficient amount of toxin to cause illness and possible death.

Staphylococcus aureus General characteristics. Staphylococcal foodborne illness (intoxication) is caused by ingestion of one or more of six heat-stable enterotoxins produced by certain strains of this species.

Small numbers of S. aureus are usually found in foods that have been exposed to or handled by food handlers. Detection of a small number S. aureus does not, however, assure the safety of the food because the organism can be killed after producing toxin. The toxins are quite stable to heat and can remain in foods to cause illness, even after being subjected to high temperatures during commercial canning procedures.

The ingestion of toxin-containing food causes illness. The toxins accumulate in food when the S. aureus cells are allowed to multiply profusely. When the toxin-containing food is ingested, it passes through the stomach and is absorbed in the intestine. The absorbed toxin triggers the vomiting center in the brain by way of the vagus and sympathetic nerve. This effect produces the feeling of nausea, salivation, and vomiting. Other effects on the central nervous system produce sweating, headache, and shallow respiration. The toxin also causes secretion of fluids from intestinal mucosa (lining of the intestine), resulting in diarrhea. Enteritis (inflammation of the intestine) develops due to mucosal cell disintegration which leads to ulceration of the mucosa and destruction of the surface lining of the intestine.

Symptoms. The symptoms usually appear within 2 to 4 hours after ingestion of food containing the toxin, but the times vary from 30 minutes to 8 hours. The symptoms include vomiting, salivation, nausea, abdominal cramps, diarrhea, headache, muscular cramps, sweating, chills, prostration, weak pulse, and shallow respiration. The severity of the symptoms varies

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with the susceptibility of the individual, the concentration of the toxin in the food, and the amount of toxin consumed.

The duration of the illness is less than 24 hours to 2 days. Mortality is extremely low. In severe cases, headache, muscular cramping and marked prostration may occur. Body temperature may be elevated or depressed and lowered blood pressure can be quite harmful in the elderly. In these severe cases, saline solutions are administered.

Toxic dose. The number of S. aureus required to produce enough toxin to cause illness is 106 organisms per gram in the food. The toxins cause inflammation of the lining of the intestinal tract of the victim, resulting in gastroenteritis.

Immunity. Considerable variation in susceptibility to this type of intoxication has been noted in tests performed with human volunteers and animals.

In outbreaks of staphylococcal food intoxication it is unusual if all individuals who consume the incriminated food become ill. The variation in amounts of food eaten and uneven distribution of the toxin in the food may be responsible. Some individuals do not seem to be affected by food containing the toxin and experience few if any symptoms of illness. This variation between people may be due to prior exposure to the specific enterotoxin and thus the development of a resistance or immunity.

Hepatitis A Virus Characteristics. This virus may be present in sewage-polluted waters and in seafood taken from these waters. People may also be the source of this virus.

The virus does not multiply in food but can remain viable in food at refrigeration or freezing temperatures.

Infective dose and symptoms. The exact number of virus particles required to cause illness is not known at this time, but is probably less than 100.

The virus is absorbed in the intestine and carried by the blood to the liver. Hepatitis A virus particles replicate within liver cells causing the characteristic symptoms listed below.

Symptoms of illness may appear in as soon as 10 days or up to 40 days after consumption. These include jaundice, abdominal pain, loss of appetite, and general malaise. Complete recovery occurs within a few months in the majority of cases, although permanent liver damage can occur.

Clostridium perfringens The illness occurs when toxin is released from cells of C. perfringens during sporulation (spore formation) in the small intestine. The toxin is absorbed into the intestinal mucosa. This causes an increased release of fluid, sodium, and chloride. Mucosal cellular function is altered and resultant symptoms occur.

It is also thought that under some conditions vegetative cells may form toxins when they sporulate in foods. The toxin is little affected by freezing or refrigerated storage of foods.

Symptoms. The symptoms of C. perfringens are similar to those of staphylococcal intoxication but are somewhat milder. Symptoms of nausea, intestinal cramps and diarrhea begin 8 to 22 hours after ingestion of the contaminated food and continue

for 6 to 12 hours. Vomiting, fever or headache is rare. The illness is seldom fatal.

Infective or toxic dose. Sufficient toxin to cause illness is released during sporulation of a cell population of about 106 per gram.

Salmonellosis Characteristics. Salmonellosis results when a sufficient number of organisms reach the small intestine and multiply in the lumen. Salmonella spp invade cells in the intestinal epithelium and multiply. As a result, the function of these cells is altered and there is a release of fluid, producing diarrhea. When Salmonella invades cells beyond the intestinal epithelium it can be absorbed in the bloodstream and carried by the blood (septicemia) to other organs and tissues of the body.

The outcome of ingesting viable Salmonella depends upon the virulence of the strain and the quantity ingested plus host factors which include age and state of health.

Reduced bactericidal activity from increased pH of gastric juice, more rapid passage of Salmonella through the stomach, or altered intestinal flora cause persons to be more susceptible to salmonellosis. Malnutrition, gastrectomy, gastroenterostomy, vagotomy, and oral administration of antibiotics influence susceptibility. General depression of resistance caused by other concomitant illnesses (e.g., cancer, nephritis, diabetes, anemia, alcoholism, sickle cell anemia, AIDS) influence susceptibility, particularly to bacteremia (carriage of bacteria in the blood stream). Apparently, previous infection with serotypes other than S. typhi does not produce acquired immunity.

Infective dose. The dose is the amount of microorganisms ingested in the food. The number of organisms that actually cause the infection depend on the age and health of the individual. For healthy adults the level of contamination must be fairly high (104 to 1010 organisms per gram of food). The number necessary to cause illness is much lower in young children, the elderly, and those whose health is otherwise compromised. The level may be as low as 1 to 10 organisms per 100 grams of food.

Age is an important determinant of susceptibility. Infants under 4 months of age have the highest incidence of salmonellosis. The incidence drops until age five, cases reported for individuals after this age reaches a level approximating that recorded for adults. In the elderly, incidence rises again, and mortality sometimes occurs.

Symptoms. Illness occurs when people eat foods containing vegetative Salmonella cells, which survive passage through the stomach to grow and multiply in the intestine. Symptoms such as abdominal cramps, diarrhea, fever, and vomiting develop within 8 to 72 hours, usually between 20 and 48 hours. (Longer incubation periods usually are associated with water-borne outbreaks.) Abdominal cramps, nausea and vomiting are common for approximately 24 hours. Headache and chills are possible Fevers are usually mild [below 100°F (37.8°C)]. Symptoms usually subside in 2 to 5 days.

Severe symptoms include: water diarrhea containing mucous and blood, severe cramping, dehydration, and convulsions.

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Complications of arthritis, myocarditis, meningitis, and pneumonia can occur. Death can result.

During the acute phase of diarrhea, 106 to 109 Salmonella per gram of feces may be excreted. These bacteria may continue to be excreted for months, rarely more than 3 months. Chronic carriers are possible. Contamination of food by a carrier is extremely likely. Salmonella from an ill person or a carrier transmitted to food as the result of poor hand washing. Even as few as 100 cells on the hands can seriously contaminate any food or food product if hand washing is not thorough.

Trichinosis Incubation and onset. The incubation period, the time between consuming infective Trichinella spiralis larvae and onset of clinical symptoms, can be from 2 days to nearly 28 days depending on the life cycle of the parasite and the number of larvae ingested. After ingestion of infected meat, the larvae are released from encysted muscle during digestion. The larvae mature into adults in the small intestine and produce new larvae. These parasites migrate through the body via the blood, invade the muscles and become fully developed, infective, encysted larvae about 17 to 21 days after initial infection.

Symptoms. Initial symptoms include: diarrhea, abdominal discomfort, rapid and sharp intestinal pain, fever, fluid buildup around the eyes. Later in the course of this infection (after larvae become encysted in muscle), tenderness, pain, or inflammation of the muscles develops. If muscle involvement is extensive and heart muscle is affected, death results.

Treatment is directed toward the relief of symptoms. There is no satisfactory treatment for trichinosis. Treatment with thiabendazole may be effective if administered within 24 hours of trichina ingestion. Corticosteroids are given to those critically ill, but the benefit of their use is in doubt.

Although ground beef is generally considered to be pure beef, it may be adulterated either by contamination from an uncleaned, common meat grinder that was previously used to grind pork or by the intentional mixing of beef and pork. If this contaminated ground beef is cooked to a rare state of doneness, infective Trichinella are not destroyed.

References: CAST (Council for Agricultural Science and Technology)

1994. Foodborne pathogens: Risks and consequences. Task Force Report No. 122. CAST, 4420 West Lincoln Way, Ames, Iowa.

Doyle, M. P., ed. 1989. Foodborne Bacterial Pathogens Marcel Dekker, Inc. New York, NY.

Doyle, M. P., Beuchat, L. R., and Montville, T. J. eds. Food Microbiology. Fundamentals and Frontiers. 2001 American Society of Microbiology. Washington, D. C.

FDA. 1993. HACCP. Regulatory Food Applications in Retail Food Establishments. Dept. of Health and Human Services. Division of Human Resource Development, HFC-60: Rockville, MD.

Frazier, W.C. and Westhoff, D.C. 1988. Food Microbiology. 3rd ed. McGraw-Hill, New York, NY.

Jay, J.M. 2000. Modern Food Microbiology. 6fth edition. Chapman & Hall Inc., New York, NY.

Mims, C.A. 1987. The Pathogenesis of Infectious Disease. Academic Press. London.


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Table 4-8 ILLNESSES ATTRIBUTED TO FOODS; A CLASSIFICATION BY SYMPTOMS, INCUBATING PERIODS, AND TYPES OF AGENTS

Illness or Disease

Agent Time for Onset of

Illness Signs, Symptoms and Severity Duration/Prognosis Sources Factors that Contribute to

Foodborne Outbreaks

Allergic or Adverse Reaction to Food Food or component of food that can cause an abnormal response in certain (sensitized) individuals.

Minutes to hours Any or a number of the following symptoms: Headache, tingling sensations Pulmonary and cardiovascular symptoms Nausea, vomiting, retching, diarrhea, abdominal cramps Eczema and hives Mental confusion

Duration and severity depend on type and amount of offending food that was ingested and degree of sensitivity of individuals. Anaphylatic shock after ingestion of an offending food can result in death. Severe allergic reactions may be treated with epinephrine.

Foods most commonly implicated in producing an allergic or adverse response in sensitive individuals include: cows milk, eggs, peanuts, seafood (fish, oysters, scallops etc.), all types of wheat products, tree nuts (walnuts, pecans, pistachios, etc.,) and corn and corn products.

Food allergies or adverse reactions to food involve a very small portion (1%) of the population. However, retailers and food producers and preparers must provide an accurate account of any ingredients in prepared products to these individuals

Incubation (Latency) Period Usually Less than 1 Hour Upper Gastrointestinal Tract Signs and Symptoms (Nausea, Vomiting) Occur First or Predominate

Fungal Agents Gastrointestinal irritating group mushroom poisoning

30 minutes to 2 hours Nausea, vomiting, retching, diarrhea, abdominal cramps

Duration depends on type of mushroom ingested; with treat-ment, recovery period can last from 24 hours to several weeks. As many as 100 deaths may result annually

Mushrooms. Possible resin-like substance in some mushrooms

Purchasing mushrooms from persons who mistake toxic mushrooms for edible varieties

Chemical Agents Copper poisoning Few minutes to few

hours Metallic taste, nausea, vomiting (green vomitus), abdominal pain, diarrhea

Mild cases usually recover within six hours. Severe poisoning can result in death

Copper in pipes and utensils combines with high-acid foods and beverages

Processing or storing high-acid food in contact with copper; faulty backflow preventer valves in vending machines that allow carbonic acid to contact copper pipes

Lead poisoning 30 minutes or longer Metallic taste, burning of mouth, abdominal pain, milky vomitus, bloody or black stools, foul breath, shock, blue gum line

Acute symptoms subside within 48 to 72 hours after treatment is begun. Therapy in mild cases lasts 3 to 5 days. Some symptoms can last for months

Lead in earthenware vessels, pesticides, paint, plaster, putty combines with high-acid foods and beverages

Processing or storing high-acid foods in lead-containing vessels or containers with lead leachable glazes; storing pesticides in same area as foods

Tin poisoning 30 minutes to 2 hours Bloating, nausea, vomiting, abdominal cramps, diarrhea, headache

Mild cases generally recover within 6 hours

Tin in tinned cans combines with high-acid foods and beverages

Using uncoated tin containers for storing high-acid foods

Zinc poisoning Few minutes to a few hours

Pain in mouth and abdomen, nausea, vomiting, dizziness

Mild poisonings usually recover within 6 hours; severe poisoning can result in death

Zinc in galvanized containers combines with high-acid foods and beverages

Storing high-acid foods in galvanized containers

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Illness or Disease Agent

Time for Onset of Illness

Signs, Symptoms and Severity Duration/Prognosis Sources Factors that Contribute to Foodborne Outbreaks

Nitrite poisoning 1 to 2 hours Nausea, vomiting, cyanosis,

headache, dizziness, weakness, loss of consciousness, chocolate-brown colored blood

If amount consumed is low, symptoms will pass; if large amount is consumed, death can result

Excessive amounts of nitrites or nitrates used as curing compound or ground water from shallow well, fertilizer

Using excessive amounts of nitrites or nitrates in foods for curing or for covering up spoilage; mistaking nitrites for common salt and other condiments; improper refrigeration of fresh produce; excessive nitrification of fertilized fields

Sodium hydroxide poisoning

Few minutes Burning of lips, mouth and throat; vomiting, abdominal pain, diarrhea

May be weeks to months, depending on amount consumed and severity of injury.

Sodium hydroxide in bottle washing compounds, detergents, or drain cleaners contaminating or remaining in bottled beverages, pretzels, seasonings

Inadequate rinsing of bottles cleaned with caustic soda; inadequate baking of pretzels; accidental addition of cleaning compound to food seasoning dispenser

Monosodium glutamate

Few minutes to 1 hour Burning sensation in back of neck, forearms, chest; feeling of tightness; tingling; flushing; dizziness; headache; nausea

Generally less than 24 hours

Excessive amounts monosodium glutamate (MSG) or free glutamic acid in foods.

Using excessive amounts of MSG as flavor intensifier

Neurologic Symptoms and Signs (Visual Disturbances, Tingling, and/or Paralysis) Occur Fish Toxins Paralytic shellfish toxin (PSP). Saxi-toxin and similar toxins from dino-flagellates; Proto-gonaulax and Gymnodinium species, which are consumed by shell fish. (Intoxication)

Minutes to 2 hours Dose = ≥100 µg

Tingling, burning, numbness around lips and fingertips, giddiness, incoherent speech, difficulty to stand, respiratory paralysis. Symptoms persist as long as toxin remains and is absorbed by host; fatalities may occur, depending upon amount ingested. (Mild to severe)

Several days Shell fish only from NE or NW coasts in U.S. and North America. [Harvesting shellfish from waters with high concentration of Protogonaulax or Gymnodinium.] Also in Central America and Asia.

Harvesting shellfish from contaminated waters.

Diarrhetic shellfish poison. (Intoxication)

30 minutes to 2 to 3 hours Dose = ≥32 - 77 µg

Nausea, vomiting, diarrhea, and abdominal pain accompanied by chills, head-ache and fever. (Mild)

2 to 3 days Consumption of mussels, oysters, and scallops taken from contaminated waters

Consumption of shellfish from unsafe waters.

Ciguatoxins (Intoxication)

Minutes to 24 hours Dose = 40 - 70 ng.

Gastrointestinal symptoms, tingling and numbness of mouth and limbs, muscular and joint pain, dizziness, cold-hot sensations, rash, weakness, slowness of heart beat, prostration, paralysis. (Mild to severe)

Gastroenteritis disappears in a few days; neurological problems may last several days; deaths occur.

Eating liver, intestines, roe, gonads, or flesh of tropical reef fishes (e.g., barracuda, grouper, red snapper, amberjack, goat fish, skip jack, parrot fish). Usually large reef fish are more commonly toxic.

Consumption of fish from unsafe waters.

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Illness or Disease



Foodborne Outbreaks Domoic acid (Amnesic Shell- fish Poisoning) (Intoxication)

Within 24 hours. Dose = ≥60 µg

Gastrointestinal symptoms (nausea, vomiting, diarrhea, and abdominal pain) accompanied by neurological problems (confusion, memory loss, disorientation, seizure, coma. (Mild to severe)

Hours to permanent Consumption of mussels and clams taken from contaminated waters.


Neurotoxic shellfish poison (brevetoxins) (Intoxication)

Minutes to hours Dose = >80 µg

Gastrointestinal symptoms (nausea, vomiting, diarrhea, and abdominal pain) accompanied by neurological problems (tingling and numbness of lips, tongue, and throat; muscular aches, dizziness, reversal of sensations of hot and cold). (Mild to moderate)

A few hours to several days.

Consumption of shellfish taken along the Southern coast of the United States (Florida and the Gulf Coast). May be associated with the Red Tide.


Scombroid (Histamine or histamine-like) (Intoxication)

Minutes to 6 hours Dose = ≥50 mg histamine

Headache, dizziness, nausea, vomiting, peppery taste, burning throat, facial swelling and flushing, stomach pain, itching of skin. (Mild to severe)

≥ 1 day to 2 days

[Histamine-like substance produced by Proteus spp. or other bacteria from histidine in fish flesh]. Fishery products: tuna (yellow fin and skipjack), mackerel, mahi-mahi, blue fish, abalone. Has also been found in Swiss cheese.

Consumption of products containing high amounts of histamine. Toxin forms in a food when certain bacteria are present and time and temperature permit their growth. Cooking, canning and freezing do not reduce toxic effect.

Tetrodoxin [Puffer fish poisoning (Intoxication)

Minutes to 3 hours Dose = ≥100 µg

Major neurological problems: numbness in face and hands, headache, paralysis, respiratory distress, speech is affected, dyspnea, cyanosis, hypotension, cardiac arrhythmia, mental impairment, and convulsions. May also be gastrointestinal involvement (nausea, diarrhea, and/or vomiting). (Moderate to severe)

Hours 50% of cases are fatal.

Consumption of Puffer fish only,. Most cases occur in Japan and in other regions of the Indo-Pacific.

No recent cases in U.S.

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Illness or Disease



Foodborne Outbreaks

Bacterial Agent Neurologic Symptoms and Signs (Visual Disturbances, Tingling, and/or Paralysis) Occur

Botulism Clostridium botulinum (Toxicoinfection) (Infant botulism) Intoxication (Adults)

2 hours to 8 days; mean = 18 to 36 hours Inf. dose = Up to about 109 LD50

* toxin in mice.

Gastrointestinal symptoms may precede neurological symptoms; vertigo, double or blurred vision, dryness of mouth, difficulty in swallowing, speaking and breathing; descending muscular weakness, constipation, pupils dilated or fixed, respiratory paralysis. In severest cases, death results within 24 hours. (Severe)

In those who survive the respiratory paralysis, symptoms may last for weeks to months. 7.5% fatality case ratio.

Found in soil, fresh-water mud, and animals. Types A, B, E, and F produce lethal neurotoxins for humans.

Canned low-acid foods (usually home canned), smoked fish, cooked potatoes, garlic in oil, coleslaw, onions, meat loaf, stew left in ovens without heat overnight, fermented fish eggs, fish, marine mammals.

Toxicoinfection for infants only. Has been traced to giving babies honey.

Most adult incidents due to home-canned or fermented foods; occasionally mishandling in foodservice. Most due to improper holding and/or preservation of vegetables (peppers, pimentos) meat, fish.

Incubation (Latency) Period 1 to 6 Hours Upper Gastrointestinal Tract Signs and Symptoms (Nausea, Vomiting) Occur First or Predominate

Bacterial Agents

Bacillus cereus gastroenteritis (emetic) Exo-enterotoxin of B. cereus; (strains differ from those cited later) (Intoxication)

1/2 to 5 hours. Usually less than 12 hours. Inf. dose = 105 to 1011

Nausea, vomiting, occasional diarrhea

Usually 6 to 24 hours Found in soil. Contaminant of cereals, spices, grains, sprouts. Common incidents involve boiled or fried rice

Holding cooked foods at room temperature or in a hot holding device at less than 122°F (50°C); too slow cooling of food to less than 41°F (5°C).

Staphylococcal intoxication Exo-enterotoxins A, B, C, D, E, or F of Staphylococcus aureus;

1 to 8 hours; mean 2 to 4 hours. Toxin produced by growth of Growth of 106 CFU/ gram of food or consumption of <1µg enterotoxin

Nausea, vomiting, retching, abdominal pain, diarrhea, pros-tration

24 to 48 hours; deaths are rare but have been recorded among the aged

Staphylococcus aureus is found in the nose and throat and skin of people and animals. Incidents occur when the organism contaminates and grows in food to high levels and produces a heat resistant enterotoxin. Can grow in salty foods.

Improper handling and storage of fermented sausages, ham, meat, and poultry products; cream-filled pastries; whipped butter; cheese; dry milk; food mixtures; high-protein leftover foods; food handlers with infected cuts and poor hygiene practices.

LD50 = Lethal dose for 50% of the population

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Illness or Disease



Foodborne Outbreaks

Incubation (Latency) Period Usually 7 to 12 Hours Lower Gastrointestinal Tract Signs and Symptoms (Abdominal Cramps, Diarrhea) Occur First or Predominate

Bacterial Agents Aeromonas hydrophila

Onset time = ? Inf. dose = unknown

Nausea, vomiting, diarrhea, and stomach cramps. Immune-compromised most susceptible.(Mild, self-limiting)

Days to weeks Has been found in fish and shellfish, as well as red meats (beef, lamb, pork) and poultry.

Cases have been noted in clinical centers, however, there has not been a fully confirmed outbreak in the U.S.

Bacillus cereus enteritis (diarrheal) Enterotoxin of B. cereus; organism in soil (strains differ from those cited earlier) (Toxicoinfection)

8 to 16 hours mean = 12 hours

Nausea, abdominal pain, watery diarrhea (Mild, self-limiting)

6 to 24 hours Found in soil. Incidents traced to cereal products, soups, custards and sauces, meat loaf, sausage, reconstituted dried potatoes, refried beans. (Spore out-growth in food. Viable cells proliferate in food and in GI tract after consumption to cause illness.)

Holding cooked foods at kitchen temperatures or in a hot holding device at less than 122°F (50°C); cooling food too slowly to less than 41°F (5°C); inadequate pasteurization during cooking or reheating; inadequate reheating of leftovers

Clostridium perfringens gastroenteritis (Toxicoinfection)

8 to 22 hours mean = 10 hours Inf. dose = 106 to 1010 CFU

Endo-enterotoxin formed during sporulation of C. perfringens in intestines. Abdominal pain, diarrhea. Rarely vomiting or nausea. Fatalities are rare. (Mild)

12 to 24 hours Spores and organisms are found in feces of infected humans, other animals, and in soil. Endo-enterotoxin forms during sporulation of C. perfringens in intestines. Incidents involve cooked meat, poultry, gravy, sauces, soups, refried beans.

Holding cooked foods at kitchen temperatures or in a hot holding device at less than 127°F (52.8°C); cooling food too slowly to less than 41°F (5°C); inadequate pasteurization during cooking or reheating

Campylobacter jejuni enterocolitis (Infection)

2 to 7 days mean = 3 to 5 days Inf. dose = ≥ 500 CFU

Diarrhea (often times bloody), severe abdominal pain, fever, loss of appetite, general feeling of ill health, headache, vomiting(Mild to moderate)

1 to 4 days; no longer than 10 days

Raw milk, poultry, beef liver, raw clams, water

Inadequate pasteurization during cooking or reheating; cross-contamination on food contact surface; use of unpasteurized dairy products; inadequate hand washing.

Escherichia coli 0157:H7 (entero-hemorrhagic) (Toxicoinfection)

3 to 7 days Inf. dose estimated to be 101 to 103 CFU

Severe abdominal pain, watery diarrhea that may become grossly bloody. Occasionally vomiting occurs. May or may not be fever. May lead to severe complications in young children, elderly and immune-compromised persons. 2 % fatality case ratio. (Moderate to severe)

Days to weeks Found in fecal material from animals and humans

Most outbreaks are associated with insufficiently cooked ground beef patties in food service establishments and in nursing homes; also associated with consumption of raw milk and unpasteurized cider.

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Illness or Disease



Foodborne Outbreaks E. coli (entero-pathogenic) (Infection ?)

1 to 6 days Inf. dose estimated to be 106 to 1010 CFU for adults

Watery or bloody diarrhea. Seen in infants and young children of third world countries. Produces verotoxin or shiga-like toxin. (Mild to moderate)

Days to weeks Fecal organism from animals and humans.

Unlikely to be a significant cause of foodborne illness in the U.S., Canada, or W. Europe. Most cases in young children in tropical areas with poor hygienic standards.

E. coli (entero-invasive) (Infection)

1 to 3 days Inf. dose = 108 CFU for adults with no underlying illness

Diarrhea or mild dysentery. May be blood or mucous in stools. Sometimes mistaken for shigellosis. (Mild to moderate)


Unlikely to be a significant cause of foodborne illness in the U.S., Canada, or W. Europe. Most cases in young children in tropical areas with poor hygienic standards.

E. coli (entero-toxigenic) (Toxicoinfection)

1 to 3 days Inf. dose = 106 to 108 CFU for adults with no underlying illness

Watery diarrhea, abdominal cramps, low-grade fever, nausea, and malaise. (Mild to moderate)


Most cases in tropical countries with poor hygienic standards. Cases in U.S. are rare; most are associated with foreign travel. Most common cause of traveler's diarrhea. Highest incidence in children < 2 years in developing countries.

Salmonellosis (Infection)

6 to 72 hours; mean 18 to 36 hours Inf. dose = 1 to about 109 CFU

Abdominal pain, diarrhea, chills, fever, nausea, vomiting, general feeling of ill health (Mild to severe)

Typically 2 to 5 days, although protracted cases may last 10 to 14 days; stool cultures may be positive for Salmonella for up to 4 weeks after illness

Various serotypes of Salmonella from feces of infected humans and animals Foodborne incidents have commonly implicated meat, poultry, raw milk, and eggs. However, numerous other foods are involved, e.g., peanuts. cantaloupe, chocolate, water melon, tomatoes

Holding cooked foods at temperatures for periods of time that allow microorganism to multiply; cooling food too slowly; inadequate pasteurization during cooking or reheating; cross-contamination between food products, particularly between raw and cooked food products; inadequate hand washing.

Shigellosis Shigella flexneri, S. dysenteriae, S. sonnei, and S. boydii (Infection)

1 to 7 days Inf. dose = 101 to 106 CFU

Abdominal pain, diarrhea, bloody and mucoid stools, fever (Moderate to severe)

Generally less than 7 days; untreated patients may shed Shigella in feces for 2 weeks or more after recovery

Fecal contamination from infected individuals, poor sewage disposal, contaminated water source. Any food can be affected through cross-contamination by infected food handler

Poor personal hygiene of infected food handlers responsible for most cases, e.g., inadequate hand washing. Reported in salads (lettuce) and water supplies.

Vibrio Cholerae (01) Cholera (Toxicoinfection)

1 to 3 days Inf. dose = 106 CFU

Profuse watery diarrhea (rice water stools), vomiting, abdominal pain, dehydration, thirst, collapse, reduced skin turgor, wrinkled finger, sunken eyes. (May be mild, usually severe)

Can last 2 to 7 days with appropriate therapy; left untreated, cholera can cause death

Feces of infected humans. Outbreaks frequently associated with seafood, contaminated water supply, and foods washed or prepared with contaminated water.

Poor sewage disposal, contaminated water source. Rare in U.S.

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Vibrio Cholerae (non-01) (Infection, toxicoinfection)


Diarrhea, (may have bloody stools) abdominal cramps, and fever; sometimes nausea and vomiting. (Mild to moderate)

Days Outbreaks associated with seafood taken from contaminated waters, mainly in shellfish from southern waters.

Harvesting shellfish from contaminated waters.

Vibrio parahaemo-lyticus (Infection)


Abdominal pain, diarrhea, nausea, vomiting, fever, chills, headache (Mild, self-limiting)

2 to 5 days Most cases are associated with sea food [marine fish, shellfish, crustacea (raw or recontaminated)]. Contaminated sea water.

Inadequate cooking; improper refrigeration; cross-contamination; improper cleaning of equipment; using sea water in food preparation or to cool cooked foods; using suppliers who do not have effective HACCP programs

Vibrio vulnificus (Infection)

Median time = 16 hours. Inf. dose = Estimate 1 CFU for persons with elevated serum iron concentration.

Organism enters blood stream to cause septic shock and death (50% fatality ratio). Individuals develop bulbous skin lesions. Amputations may be required. (Severe complications)

Days to weeks All known cases associated with seafood, especially raw oysters taken from contaminated waters. Susceptible individuals are those with underlying chronic disease (particularly liver disease). Most victims are male and have chronic liver or blood related disorders.

Consumption of raw oysters, inadequate cooking of oysters and other shellfish.

Yersinia enterocolitica (Infection)

1 to 3 days Inf. dose = 3.9 x 109 CFU

Gastroenteritis with diarrhea, and/or vomiting; fever and abdominal pain are common symptoms. Sometimes mimics appendicitis. Longer term effects are linked to reactive arthritis and Reiter's syndrome. (Mild to moderate, self-limiting to chronic)

Days to weeks Carried by swine. Associated with pork, raw milk, or milk products, carried by swine.

Cross-contamination of products, failure to heat products to pasteurization temperatures, improper storage, poor sanitation techniques by food handlers.

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Illness or Disease



Foodborne Outbreaks

Incubation (Latency) Period Usually Greater than 72 Hours Generalized Infection Symptoms And Signs (Fever, Chills, Malaise, and/or Aches) Occur

Bacterial Agents Listeriosis (Listeria monocytogenes) (Infection)

4 to 21 days

Inf. dose = >103 to >105 CFU

Fever, headache, nausea, vomiting, diarrhea precede complications of stillbirths, meningitis, encephalitis, sepsis. In healthy adults, "flu-like" symptoms may pass within a week; the pathogen is a great hazard to pregnant women and their unborn fetuses; L. monocytogenes is a cause of stillbirths and abortions; this pathogen also causes death in immune-compromised individuals. (Mild to severe)

4 to 21 days Found in the soil and fecal material of infected humans and animals. Foods implicated in outbreaks include coleslaw, lettuce, milk, cheese, animal products, frankfurters.

Inadequate pasteurization during cooking or reheating, failure to properly pasteurize milk, prolonged refrigeration above 32°F (0°C)

Salmonella typhi and paratyphi [Typhoid or Paratyphoid Fevers] (Infection)

7 to 28 days Inf. dose = <103 to 109 CFU

Malaise, headache, fever, cough, nausea, vomiting, constipation, abdominal pain, chills, rose spots, bloody stools. 10% fatalities (Severe)

Weeks to months. Possible relapses.

Fecal material from animals and humans. Virulent form of Salmonella. Usually traced water or infected carriers; poor sewage disposal.

Outbreaks frequently waterborne; contaminated shellfish or foods handled by carriers and not subsequently heated. Rare in U.S.

Mycobacterium bovis, avium, and tuberculosis (Infection)

Weeks to months Inf. dose = 106 CFU for adults

Cause of tuberculosis. Not highly infectious, however only a few organisms are needed to cause disease. First stage is silent, may or may not have fever. Second stage: reinfection, lesions develop in lungs and possibly other tissues. Degenerative disease (Severe)

Weeks to months. Mycobacterium spp. are found in soil, water, and animals. Can be transmitted in unpasteurized milk, meat, poultry or fish.

Consumption of raw milk, contaminated water, and inadequately pasteurized meat, fish, and poultry products. Currently, not thought to be foodborne in the U.S.

Brucillosis (Brucela abortus) (Infection)

Onset = ?

Inf. dose = ?

Fever, profuse sweating, chills, weakness, malaise, body aches, chest and joint pains, weight loss, and anorexia. (Moderate to severe)

Weeks Found in animals (cows, sheep, goats, etc.) and humans.

Foodborne incidents have included unpasteurized goat milk and cheese.

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Illness or Disease



Foodborne Outbreaks Coxiella burnetii (Q Fever) (Infection)

2 to 4 weeks Inf. dose = ?

Initial fever, followed by malaise, anorexia, muscular pain, and intense headache. (may be misdiagnosed as influenza). (Mild to severe)

Days to weeks Found in wild and domestic animals. Most incidents have involved

drinking raw milk.

Consumption of raw milk. Controlled by drinking or using only pasteurized milk.

Incubation (Latency) Period 13 to 72 Hours Sore Throat and Respiratory Signs and Symptoms

Streptococcal infections. (Strepto coccus Group A) Streptococcus pyogenes from throat and lesions of infected humans

1 to 3 days Inf. dose = Less than 103 CFU

Sore throat, fever, nausea, vomiting, rhinorrhea, sometimes a rash.

Generally 5 to 7 days; fever may persist up to 9 days in children. Tonsils may remain swollen up to 6 months

Found in the nose, throat and skin of infected individuals. Infected persons transmit bacteria to food (particularly cooked foods held at growth temperatures), milk, salads, custard, rice, etc.

Persons with skin infections touching or coughing into cooked foods; inadequate pasteurization during cooking or reheating; inadequate hand washing; poor food handling practices; cross-contamination.

Viral Agents Norwalk agent gastroenteritis (norovirus)

16 to 48 hours Inf. dose = unknown

Nausea, vomiting, abdominal pain, diarrhea, low grade fever, chills, general feeling of ill health, loss of appetite, headache(Mild to moderate)

48 hours; infected persons may spread disease 2 to 3 days after recovery

The virus can be transmitted by humans, water, seafood (clams, oysters, cockles), green salads, pastry, frostings (any food prepared by infected workers.)

Sewage pollution of shellfish growing waters; inadequate hand washing

Hepatitis A (Infectious hepatitis)

10 to 50 days mean 25 days Inf. dose = unknown

Fever, general feeling of ill health, loss of appetite, tiredness, nausea, abdominal pain, jaundice(Moderate to severe)

Typically jaundice lasts 6 to 8 weeks; full recovery is usually seen after 3 to 4 months

Hepatitis A virus from feces, urine, blood of infected humans and other primates. Can be transmitted in food, especially raw shellfish, salads, cold cuts; food handlers; water

Inadequate hand washing; inadequate pasteurization during cooking or reheating; using suppliers without effective HACCP programs; harvesting shellfish from sewage-contaminated waters; improper sewage disposal

Parasitic Agents Giardia lamblia (Infection)

5 to 25 days Inf. dose = 1 or more viable cysts

Abdominal pain, mucoid diarrhea, fatty stools (Mild to moderate)

Weeks to years Contaminated water supply. Contaminated vegetables, problem for day-care centers.

Use of unsafe water.. Cross-contamination. Poor personal hygiene and inadequate hand washing by infected food handler.

Cryptosporidium parvum (Infection)

1 to 2 weeks Inf. dose = < 30 cysts

May be asymptomatic. Frequently is characterized by severe watery diarrhea. Pulmonary or tracheal cryptosporidiosis is associated with coughing and low grade fever accompanied by severe intestinal distress. (Moderate to severe)

4 days to 3 weeks Contaminated water supply, marine fish, possibly associated with raw milk and raw vegetables, infected food handler, problem for day-care centers.

Use of unsafe water or raw milk. Cross-contamination. Inadequate hand washing by infected food handler.

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Amebic dysentery Entamoeba histolytica (Amebiasis)

2 to 4 weeks Inf. dose = 1 viable cyst

May be asymtomatic, or may produce vague gastrointestinal distress, dysentery with blood and mucus. May produce intestinal blockage (Mild to severe)

Usually weeks to months, but may continue for years

Contaminated drinking water, contaminated raw vegetables. Large outbreak did occur at U.S. World's Fair in Chicago in 1933. Was due to defective plumbing (sewage) contaminating potable water.

May be acquired when traveling in third-world countries. Occurs in crowded situations where there is poor personal hygiene. Rare in the U.S..

Toxoplasma gondii (Infection)

10 to 13 days Inf. dose = 1 or more viable cysts

Fever, headache, aching muscles, rash. Severe complications in pregnant women; can cause birth defects and mental retardation of infants; fatalities occur in infants and adults. (Mild to severe)

Weeks to years Found in pork, beef, veal, and lamb. May be carried by rats, cats, and dogs.

Failure to cook pork, beef, veal, and lamb sufficiently, or consumption of these same raw meats.

Other Parasites Anisakiasis (Anisakid nematodes Anisakis, Phocanema, Porrocaecum) (Infection)

4 to 6 hours Inf. dose = 1 larva

Stomach pain, nausea, vomiting, abdominal pain, diarrhea, fever (Mild to severe)

Symptoms persist as long as parasite survives within host

Marine fish, rock fish, herring, cod, squid that carry anisakid nemitodes.

Consumption of inadequately cooked or raw fish that contain the anisakid nemitodes.

Taeniasis (Beef Tapeworm infection, Taenia saginata from flesh of infected cattle) (Infection)

8 to 14 weeks Inf. dose = 1 cyst

Vague discomfort, hunger pain, loss of weight, abdominal pain (Mild to severe)

Symptoms persist as long as worms and eggs remain in the intestine; as long as 30 years

Raw insufficiently cooked beef Using suppliers without effective HACCP programs; inadequate pasteurization during cooking and reheating; inadequate sewage disposal; sewage contaminated pastures

Taeniasis (Pork Tapeworm, Taenia solium from flesh of infected swine) (Infection)

8 to 14 weeks Inf. dose = 1 cyst

Vague discomfort, hunger pains, loss of weight (Mild to severe)

Symptoms persist as long as parasite is present in host; may affect eyes causing blindness; fatalities occur when heart muscle and central nervous system are affected

Raw or insufficiently cooked pork Using suppliers without effective HACCP programs; inadequate pasteurization during cooking and reheating; improper sewage disposal; contaminated pastures

Diphyllobothrium spp. (Fish tapeworms) (Infection)

About 10 days after consumption. Inf. dose = 1 larva

Anemia (Mild to severe)

As long as parasites remain in host

May be found in fresh water fish, tuna, salmon, red snapper.

Transmitted when fresh water fish, tuna, salmon, red snapper are under cooked or eaten raw.

Trichinella spiralis (Infection)

4 to 28 days (mean = 9 days) Inf. dose = 1 larva

Gastroenteritis, fever, swelling about eyes, muscular pain, chills, prostration, labored breathing. Fatalities occur if vital organs are invaded. (Moderate to severe)

Severe symptoms may last up to 6 weeks; muscle pain may persist indefinitely

May be present in raw pork, game meat, bear meat, and walrus meat.

Inadequate pasteurization during cooking and reheating; eating raw or inadequately cooked pork or bear meat, inadequate cooking or heat processing; feeding uncooked or inadequately heat-processed garbage to swine; rats in swine-producing areas.

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References: Archer, F.E., and Young, F.E., 1988. Contemporary issues: Diseases with a food vector. Clin. Microbiol. Rev. 1:377-398. Benenson, A.S., 1990. Control of Communicable Diseases in Man, 15th Edition, American Public Health Assoc., Washington, D.C. CAST (Council for Agricultural Science and Technology) 1994. Foodborne pathogens: Risks and consequences. Task Force Report No. 122. CAST, 4420 West Lincoln Way,

Ames, Iowa. Doyle, M.P., ed., 1989. Foodborne Bacterial Pathogens. Marcel Dekker, Inc., New York, NY. FDA, 1993. HACCP. Regulatory Food Applications in Retail Food Establishments. Dept. of Health and Human Services. Division of Human Resource Development, HFC-60;

Rockville, MD. IAMFES. 1987. Procedures to Investigate Foodborne Illness, 3rd Edition, Ames, IA. Mossel, D.A.A. 1988. Impact of foodborne pathogens on today's world, and prospects for management. Animal and Human Health. Vol. 1 (1):13-23/ Murray, P.R., Baron, E.J., Pfaller, M.A., Tenover, F.C., and Yolken, R.H., 1995. Manual of Clinical Microbiology. 6th edition. American Society for Microbiology,

Washington, D.C.

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1/20/2005 1901(4a) 161314

Severe Hazard• The organism is critical in determining the safety

of the food. Illness is sometimes fatal.

Moderate Hazard, Special Risk• The organism is widely distributed in nature. • There is likely to be a secondary spread from an

infected person. Illness is not fatal.

Moderate Hazard, No Special Risk• The organism is widely distributed in nature.

Secondary transmission is unlikely. Illness is not fatal.

GROUPING PATHOGENS BY SEVERITY OF THE HAZARD

Grouping Pathogens by Severity of the

Hazard Grouping Microorganisms Pathogens can be grouped into three categories according to the severity of the hazard each presents. Although there are many diseases caused by microorganisms, only a couple dozen are transmitted by foods. Each year the Centers for Disease Control (CDC) reports investigations of disease outbreaks directly related to food. There are about 15 organisms implicated in these various outbreaks. The severity of each case and the frequency of outbreaks related to each organism varies. The grouping outlined here parallels that of the International Commission on Microbiological Specifications for Foods (ICMSF) and agrees generally with the program outlined by the Subcommittee on Microbiological Criteria for Foods and Food Ingredients of the National Research Council (NRC).

Severe Hazards Certain organisms are critical in determining the safety of foods. Some bacteria are very virulent and not only survive and multiply in humans but seriously damage health and threaten life. Those regarded as severe hazards include:

Clostridium botulinum • • • • • •

•

Listeria monocytogenes Vibrio cholerae Salmonella typhi and Salmonella paratyphi Hepatitis A virus Fish and shellfish toxins including ciguatera and paralytic shellfish poisoning (PSP) Enterohemorrhagic Escherichia coli

Botulism frequently results in death. Cholera may be fatal. Mild cholera infections do occur and often are not even recognized as being a foodborne illness. Although most Salmonella spp. cause only gastroenteritis, the severity of typhoid and paratyphoid fevers, the need for prolonged medical care, and the low infective dose cause these species to labeled as severe hazards.

Likewise, hepatitis A viral infections may range from asymptomatic to acute liver disease. The severe debilitation and death which may result plus the difficulty in tracing the

source of the original viral cells are causes for placement in this category.

PSP (paralytic shellfish poisoning) intoxication frequently results in respiratory failure and death. Ciguatera toxins which accumulate in fish flesh cause gastrointestinal and neurological symptoms with disabilities lasting several days to many months, even years.

Moderate Hazards Considering the etiological, clinical, and epidemiological manifestations of the organisms, moderately hazardous pathogens may be subdivided into those that present special epidemiological risks and those that do not. The first group is termed moderate hazard with potentially extensive spread. The others are listed as moderate hazards with limited spread.

Moderate hazards with potentially extensive spread. Salmonella, pathogenic Escherichia coli, Streptococcus pyogenes, and Vibrio parahaemolyticus are classified in this category. All are hazardous, widely distributed, but resultant illnesses are usually not fatal. They are initially spread by specific foods but there may be secondary spread due environmental contamination and cross-contamination within processing plants and food preparation areas. The illness dose may be low, depending on strain and nutritional and health status of affected individuals.

Moderate hazards with limited spread. Organisms that do not present special epidemiological risks include: Bacillus cereus, Clostridium perfringens, Yersinia enterocolitica, Campylobacter jejuni, Trichinella spiralis, Staphylococcus aureus and histamine from scombroid and other fishes. These infection- or toxin-producing microorganisms are usually found in small numbers in many foods. Generally, illnesses are only caused when there are large numbers of the pathogens or when enough time elapses to produce sufficient toxin to cause illness. Outbreaks are usually restricted to consumers of a particular meal or a particular kind of food.

Clear delineation between pathogens in these two moderate hazard categories does not exist. The full importance of Yersinia, Campylobacter, and Vibrio parahaemolyticus are yet to be determined. All are being seen more frequently. The risk of secondary spread is not known.

Primary pathogens, those most frequently seen and those commonly endured without report, are not significantly hazardous. The hazard will depend on the health of the consumer.

Foodservice units in hospitals and extended care units should avoid contamination at all levels. Food obtained and prepared for most households, restaurants, and other commercial food dispensing units usually is expected to contain contamination by organisms in the moderate hazard category.

Summary Table 4-9 shows infection and toxin-producing organisms, grouped by hazards.

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Table 4-9 Infection and Toxin-Producing Organisms, Grouped by

Hazards* Severe Hazards – Death, severe debilitation, respiratory failure, or neurological disability often result.

Clostridium botulinum Salmonella cholerae-suis Vibrio cholerae Listeria monocytogenes Vibrio vulnificus Shigella spp. Salmonella typhi Brucella abortus Salmonella paratyphi A, B, C Brucella melitensis Mycobacterium bovis Brucella suis Hepatitis A virus Enterohemorrhagic Escherichia coli (E. coli O157:H7) Fish and shellfish toxins (Ciguatera, Paralytic shellfish

poisoning) Mycotoxins (Possibly cancer inducing) Moderate Hazards with Extensive Spread - Illness is serious, but not usually fatal. Secondary spread through processing is quite likely.

Salmonella spp. Pathogenic Escherichia coli Streptococcus pyogenes

Moderate Hazards with Limited Spread - Much milder illness results. Illness usually only occurs when foods contain large numbers of pathogens, or when toxins have been produced in foods by large numbers of pathogens.

Staphylococcus aureus Trichinella spiralis Clostridium perfringens Campylobacter jejuni Bacillus cereus Vibrio parahaemolyticus Yersinia enterocolitica Coxiella burnetii Histamine poisoning

* Adapted from NRC 1985. An Evaluation of the Role of

Microbiological Criteria for Foods and Food Ingredients. pp. 77-78. National Academy Press, Washington, D.C.

References: International Commission on Microbiological Specifications

for Foods. International Association of Microbiological Societies. 1986. Microorganisms in Foods. 2. Sampling for Microbiological Analysis: Principles and Specific Applications. 2nd edition. University of Toronto Press, Toronto, Ontario, Canada.

National Research Council. Food Protection Committee. Subcommittee on Microbiological Criteria. 1985. An Evaluation of the Role of Microbiological Criteria for Foods and Food Ingredients. National Academy Press, Washington, D.C.

Wekell, M.M. 1986. Seafood poisoning. Presented to International Association of Milk, Food and Environmental Sanitarians, Inc. 73rd Annual Meeting, Minneapolis, MN.

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• Grows with or without air

• Survives freezing temperatures

• Grows between 41 and 115ºF, in or on most foods

• Source is infected animals, birds,reptiles, and people

• Common contaminant of raw foods of animal origin (poultry, eggs, beef, pork)

• Vegetative cells multiply in intestinal tract to cause illness

• Infective dose = 10 to >10,000 cells in a portion of food

• Vegetative cells killed by pasteurization

CHARACTERISTICS OF SALMONELLA

Salmonella spp. – Characteristics

Bacterial Characteristics Salmonella spp. are gram negative, facultative aerobic rods that ferment glucose to form gas, and do not form spores. There are over 2,000 serotypes of Salmonella. All species and strains are pathogenic to humans. Sources Salmonella spp. are found in the intestinal tract of infected animals and people. They have been isolated from many species of animals such as chickens, ducks, turkeys, cows, swine, turtles, cats, dogs, hamsters, doves, pigeons, parrots, sheep, seals, donkeys and others.

A variety of raw and processed foods have been found to carry Salmonella. Raw meat and poultry, shellfish, grade A shell eggs, cracked shell eggs, and eggs removed from the shell; processed meat, poultry, and egg products; dried milk; and cheese made from unpasteurized milk have been major sources. Some other foods that have been incriminated occasionally are dried coconut, dried cereal, smoked fish, spices, nuts, vegetable gum, and others.

The list of prepared menu items frequently implicated is headed by protein menu items such as meat and poultry; mixtures containing meat, poultry, eggs and seafood; dressings and gravy; salads made with meat, poultry, egg, and seafood; puddings, cream-filled pastries, custards, cream-filled cakes, meringue pies; and many others.

The appearance, odor, and flavor of food items containing hazardous levels of Salmonella are usually not noticeably altered.

Potential or actual problems that influence transmission of Salmonella emerge when new kinds of foods are processed by customary or new methods, or when traditional foods are processed by modified or new methods. These problems are intensified when these products are marketed in increased quantity. Some examples of foods that have led to outbreaks of salmonellosis are cake mixes containing unpasteurized dried eggs, turkey rolls, roast beef cooked in meat processing plants, instantized dry milk, and food supplements containing yeast and cottonseed protein.

For example, inadequately processed eggs were used to make ice cream. Over 14 outbreaks of salmonellosis (9,000 cases) occurred in 4 eastern states within a period of 13 days. The vehicle of transmission was the contaminated ice cream.

The ecological habitat of Salmonella is the intestinal tract of both warm- and cold-blooded animals. Salmonellae can develop a resistance to antibiotics in the animal or human host. The organism exists throughout the world and spreads through fecal contamination of food, usually during slaughtering. The food at this stage is not yet adequately pasteurized. One laboratory-confirmed outbreak of foodborne salmonellosis involved 57 people who, after eating beef, developed acute gastroenteritis. One person died. Salmonella organisms were isolated from the meat and from organs of the person who died.

People are the only source of Salmonella typhi, which causes typhoid fever. Food handlers with no symptoms who are carriers of this disease can spread this pathogen by contaminating foods and beverages they touch. In 1908, a classic example of an asymptomatic carrier, Typhoid Mary from Brooklyn, New York, was reported. Water contaminated with raw sewage is also a source of Salmonella typhi.

Salmonellosis is one of the most important food-transmitted illnesses in the country. More outbreaks occur in the summer and autumn than in other seasons of the year. The incidence of salmonellosis has risen more than 20-fold since 1946. One reason may lie in the expansion of centralized processing and bulk distribution of processed food items. An example is an outbreak of salmonellosis from eating contaminated shrimp, involving 9,000 persons attending 190 parties, all served by a single catering service. Raw shrimp had been purchased at one unsanitary outlet and was then transported to another place for boiling. The boiled shrimp, still warm, were returned to the containers in which the raw shrimp had arrived. They were then transported in an unrefrigerated truck to the places of service and finally were served. By then, 7 or 8 hours had elapsed. Obviously, the cooked shrimp were recontaminated when they were placed in the containers in which the raw shrimp had been packed and the Salmonella had multiplied to an infective dose level. This incident emphasizes the critical control procedure of never placing cooked, pasteurized food back into a container that has been used for raw food, unless that container has been washed and sanitized.

Multiplication (Growth)* in Foods Salmonella spp. have simple nutritional requirements, and will grow in media containing only salt and glucose. Salmonella require only simple sugars and inorganic nitrogen to grow. The rate of growth is greater, however, in foods that contain many nutrients.

Salmonella spp. do not compete effectively with many of the naturally occurring food spoilage microorganisms in food and high spoilage plate counts are a safety factor.

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* Note: The words "multiply" and multiplication" will frequently be replaced by "grow" and "growth," since they are often used interchangeably.

Salmonella grows in the presence or absence of air. The temperature range for growth is reported to be 41 to 115°F (5 to 41°C). It can survive in frozen food at freezing temperatures. It grows well on or in food with a neutral pH. Optimal pH for growth is near 7.0 (6.6 to 7.5 depending on the medium). There is no growth below 4.1 (except in the special case of Salmonella newport, which may grow in apple juice and cider at pH 3.68). In most operating situations a pH below 4.05 will not support growth. An aw below 0.945 also prevents growth unless the medium is very rich in nutrients.

Symptoms Vegetative cells cause illness by multiplying in the small intestine. Because it is an infection, the presence of only a few cells can cause illness. There are approximately 3 million cases of salmonellosis in the U.S. each year, which may result in as many as 2,000 deaths per year.

Symptoms such as abdominal cramps, diarrhea, fever, and vomiting develop in 8 to 72 hours, usually between 20 and 48 hours. Persons most susceptible to Salmonella include the elderly, children under age 5, people recovering from a severe bout with the flu or otherwise physically weakened, and people who have been ingesting antibiotics for any length of time. An outbreak in April 1985 of milk-borne salmonellosis in Illinois illustrated this problem; the fatalities were children.

The gastroenteritis syndrome presents a wide range of signs and symptoms. Stools may be few but watery. There may be bloody, mucoid diarrhea and tenesmus. Massive diarrhea with dehydration, convulsions, and death can result. Abdominal cramps, nausea, and vomiting are common for approximately 24 hours. Headache and chills are possible but any fever is usually mild [below 100°F (37.8°C)]. Typically the symptoms subside in 2 to 5 days. However, chronic arthritic symptoms may follow 3 to 4 weeks after onset of acute symptoms.

During the acute phase of diarrhea, 106 to 109 Salmonella per gram of feces may be excreted. If 0.01 g of the feces remains on the fingertips after using the toilet, the fingertips could contain 107 Salmonella. This number is more than enough to cause a foodborne illness. Organisms may continue to be excreted for 2 to 3 months. In general, carriers are over 30, female, and have had typhoid. Contamination of food by a carrier is extremely likely. Salmonella from an ill person or a carrier may remain on the carrier's hands after poor hand washing. Even as few as 100 cells on a foodservice worker's hands can seriously contaminate a wet food such as lettuce if hand washing is not thorough. This can eventually lead to foodborne illness, especially in an immune-compromised individual.

Infective Dose The dosage required to cause illness and the type of illness varies with the invading species and serotype. D'Aoast (1985) in his review article states that a single Salmonella bacterium can be infective. This statement followed the report of incidents in which fewer than 50 cells of S. napoli or fewer than 100 cells of S. eastborne in chocolate bars, and of 100 to 500 cells of S. heidelberg or 1 to 6 cells of S. typhimurium in cheddar cheese caused illness. The FDA HACCP manual (1993) states that the infective dose is few as 15 to 20 cells.

In the spring and summer of 1989, the Minnesota Department of Health reported that 4.7 cells S. javiana per 100 grams of mozzarella, string, or processed cheese contained sufficient numbers to cause illness. It appears that the fat content in these foods coats the surface of the microorganisms and enables them to survive passage through the acidity of the stomach (pH 2.0). The salmonellae are then able to multiply in the intestinal tract and cause illness.

In human volunteer studies, 1.25 x 105 S. bareilly produced illness in one volunteer and as many as 1010 S. pullorum were required to produce illness in other volunteers. The larger the dose of Salmonella spp., the more obvious the signs and severe the symptoms. A high number (105 or more) typically occurs in foodborne salmonellosis because Salmonella spp. multiply and reach these numbers in contaminated foods during periods of improper food handling.

Doses of S. typhi required to cause illness in human adults have also been investigated. When 1,000 cells were ingested, no illness resulted. When a group of 116 volunteers each ingested 105 cells, 28% of the volunteers became ill. The median incubation period of the disease for those who ingested 105 cells was 9 days; for those who ingested 109 cells, 3 days. Salmonella typhi was recovered from the stools of the infected volunteers for periods ranging from 1 to 34 days (mean, 11 days) after digestion.

A chiffonade-type dessert, which was a vehicle for a large outbreak of salmonellosis, contained 113 Salmonella per 75-gram serving. Interestingly, the initial level in the product when freshly prepared was more than 10,000 per 75-gram serving. Freezer storage at -4°F (-20°C) for 1 month caused a 2-log reduction in the initial Salmonella population (Armstrong et al., 1970).

The outcome of the infection that follows ingestion of viable Salmonella is determined by the virulence or invasiveness of the serotype and strain; the number of cells ingested; and host resistance factors such as age, nature of the alimentary tract, and state of health. Most Salmonella produce an enteric infection manifested by diarrhea, but some serotypes such as S. typhi, S. paratyphi A, B, and C, and S. cholerae-suis, tend to produce bacteremia (presence of viable microorganisms in the blood) which leads to septicemia.

All age groups are susceptible, but symptoms are most severe in the elderly, infants and the infirm. AIDS patients suffer salmonellosis frequently (estimated 20-fold more than the general population) and suffer recurrent episodes.

Incidence It is estimated that there is an annual incidence of about 1.3 million cases of salmonellosis in the United States which may result in as many as 15,000 hospitalizations and 550 deaths per year (Mead et al., 1999).

Food Analysis Conventional culture methods require 5 days for presumptive results. However, several rapid methods of analysis have been developed which require 2 days or less.

Epidemic Salmonella enteritidis Due to Eggs Epidemics of salmonellosis caused by Salmonella enteritidis in Europe and the United States in the late 1980s and early

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1990s were traced to hen's eggs. It was determined that S. enteritidis is transferred from the infected ovaries of laying hens to the egg yolk before the shells are formed. Consequently, intact Grade A eggs have been the source of this bacterial infection. In 1988, whole flocks of chickens and crates of eggs were destroyed in England. In 1988 that over 2,000 people on the Northeast coast of the United States became ill and 11 of them died due to consumption of S. enteritidis contaminated eggs.

In October 1989, 11 outbreaks of Salmonella enteritidis in Pennsylvania involved over 300 cases. In one nursing home incident, 6 elderly patients died as a result of the illness.

Another episode was reported about a man in his 40s who was reported to be in good health before consuming pie that had been highly contaminated with S. enteritidis. He became very ill and died a few days later. Several kinds of pies (cream, custard, meringue) all with shell egg ingredients were baked in a restaurant bakery and stored for 2 1/2 hours in a walk-in cooler. The pies were then picked up and carried in the trunk of a car to the site of a company party where they were consumed 3 to 6 hours later. Leftover pie was consumed that evening and the following day after having been kept unrefrigerated for as long as 21 hours. All together 14 people became ill because of this incident and several were hospitalized. The man who died delayed seeking medical treatment for his illness, and his cause of death was listed as being due to extreme dehydration as a result of Salmonella enteritidis gastroenteritis. This incident illustrates poor storage practices that allowed the population of microorganisms to grow to a level that produced severe illness in otherwise healthy individuals.

Illness incidents due to S. enteritidis emphasize the importance of: (1) not eating raw or undercooked eggs [especially young children, the elderly, and immune-compromised persons], (2) using pasteurized egg products (liquid or in-shell) in hospitals, nursing homes, foodservice establishments, day care centers, elementary schools, and commercial kitchens, (3) storing eggs at 41°F (5°C) or less, and (4) cooking shell eggs until all parts of the egg reach a temperature of 145°F (63°C) for 15 seconds. Casseroles and other dishes containing eggs should be cooked to 160°F (71°C).

Culture-confirmed cases of Salmonella enteritidis in the U.S. peaked in 1989 and the numbers of people affected with this illness since that time has been declining. The U.S. Department of Agriculture published regulations in February of 1990 establishing a mandatory testing program for egg-producing breeder flocks. This type of testing, along with other measures, has lead to a reduction in the number of cases of salmonellosis caused by the consumption of Grade A whole shell eggs.

OUTBREAK EXAMPLE I. MMWR 2000. 49 (4): 73-79.

Salmonella enteritidis Girl Scouts, Los Angeles County, California. In August 1997, the Los Angeles County Department of Health Services (LACDHS) received reports of gastrointestinal illness in members of a Girl Scout troop and some of their parents. The ill persons had eaten food prepared in a private residence by the scouts. Stool cultures were taken

from 12 ill persons yielded Salmonella enteritidis. Stool cultures taken from 12 ill persons yielded S. enteritidis.

An investigation by the health department found that of 17 persons at the dinner, 13 had gastrointestinal illness consistent with salmonellosis. Cheesecake served at the dinner was associated with illness; all 13 ill persons and two well persons ate the cheesecake. The cheese cake contained raw egg whites and egg yolks that were cooked in a double boiler until slightly thickened. The California Department of Health Services and the Department of Food and Agriculture investigated the farm that supplied the eggs and found S. enteritidis contamination. Of 476 environmental cultures taken from manure, feed, and water, 21 yielded S. enteritidis. All positive cultures were from manure. S. enteritidis was also isolated from one of 200 pooled egg samples obtained at the farm. On the basis of these findings, the layer flack was depopulated to prevent further S. enteritidis cases.

This outbreak illustrates transmission of S. enteritidis to eggs from a diseased flock of laying hens. It also illustrates the consequences of consuming raw eggs or undercooked eggs.

OUTBREAK EXAMPLE II. MMWR 1999 48 (27): 582-585.

Outbreak of Salmonella Serotype Muenchen Infections Associated with Unpasteurized Orange Juice -- United State and Canada, June 1999. During June 1999, health departments in Oregon and Washington investigated clusters of diarrheal illness attributed to Salmonella Serotype Muenchen infections in each state. Both clusters were associated with a commercially distributed unpasteurized orange juice traced to a single processor, which distributes widely in the United States. By July 13 of 1999 there were 207 confirmed cases associated with this outbreak having been reported from 15 states and two Canadian provinces. An additional 91 cases were being investigated.

In a case control study in Seattle, Washington of nine ill and 29 well restaurant A patrons, illness was significantly associated with drinking smoothies containing orange juice. Further collection of epidemiological data in the State of Washington of 85 persons with illness indicated that sixty-seven (67) patients reported drinking unpasteurized orange juice produced by a company in Tempe, Arizona, or eating at an establishment where the juice was served. The predominant symptoms reported were diarrhea (94%), fever (75%), and bloody diarrhea (43%). Ten (10%) of the patients were hospitalized. No patients died.

On the basis of epidemiologic information from investigations of health departments from the states of Washington and Oregon, and the Food and Drug Administration (FDA), the company producing the orange juice issued a recall. The unpasteurized orange juice was distributed in Arizona, California, Colorado, Nevada, New Mexico, Oregon, Texas, Utah, Washington, Wisconsin, and the Canadian provinces of Alberta and British Columbia under 7 different brand names. The juice was distributed to hotels, restaurants, and supermarkets, and was served in individual glasses as "fresh squeezed" juice in hotels and restaurants. In addition, a frozen form of the unpasteurized juice was sold for use in restaurants and institutions.

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Samples of juice from a previously unopened container of suspect orange juice analyzed by an FDA laboratory and a Washington State Public Health laboratory yielded S. Muenchen. Isolates from a smoothie blender and juice dispenser at a restaurant yielded Salmonella serogroup C2. Juice samples obtained from the juice processing facility yielded S. Hildalgo, S. Javianna, S. Gaminara, and S. Alamo, in addition to S. Muenchen.

The FDA published a final rule for the labeling of fruit and vegetable juices that includes a warning statement to advise consumers of the risks associated with drinking unprocessed juices. However the labeling requirements do not apply to juice or products containing juice that are not packaged (i.e., sold by the glass) in retail establishments. In Washington, some consumers were unaware that they were drinking unpasteurized commercial orange juice in their fruit smoothies.

OUTBREAK EXAMPLE III. J. Food Prot. 1999 62 (2): 118-122.

Salmonella Thompson associated with improper handling of roast beef at a restaurant in Sioux Falls, South Dakota. In October 1996, an outbreak of 52 Salmonella serotype Thompson infections were associated with a restaurant in Sioux Falls, South Dakota. The infections were identified among employees and patrons at the restaurant and at three luncheons catered by the restaurant. Epidemiologic investigation documented that the outbreak was caused primarily by roast beef.

Several facts suggest that a single contaminated roast beef could explain all the Salmonella Thompson infections among the restaurant patrons and among those who attended the catered luncheons the following week. First, three patients became ill after consuming contaminated roast beef served at brunch on September 29. Leftover roast beef was probably used on Greek salads served on October 5 and then again on October 7.

Salmonella can be cultured from 1 to 5% of raw beef and Salmonella Thompson is among commonly isolated serotypes from bovine sources. An inadequate internal cooking temperature might have allowed the contaminating organisms to survive. Puncturing raw meat with a temperature gage or a knife could have also caused internal contamination that might have survived the cooking process. Subsequently, inadequate refrigeration temperature could have allowed Salmonella to multiply. (The walk-in refrigerator had a temperature of 50°F).

This outbreak was probably preventable. The roast beef should have been cooked to temperatures and times that are sufficient to achieve a 5-log kill of Salmonella. The cooked roast beef should have been cooled properly and stored at refrigeration temperatures below 41°F.

References: Armstrong, R.W., Fodor, T., Curlin, G.T., Cohen, A.B.,

Morris, G.K., Martin, W.T., and Feldman, J. 1970. Epidemic Salmonella gastroenteritis due to contaminated imitation ice cream. Am. J. Edpidemiol. 91(3): 300-307.

Center for Disease Control. 1999. Outbreak of Salmonella serotype Muenchen infections associated with unpasteurized orange juice -- United States and Canada, June 1999. MMWR 48 (27):582-585.

Center for Disease Control. 2000. Outbreaks of Salmonella serotype enteritidis infection associated with eating raw or undercooked shell eggs. United States, 1996-1998. MMWR 49 (4): 73-79.

D'Aoust, J.Y. 1985. Infective Dose of Salmonella typhimurium in cheddar cheese. Am. J. Epidemiol. 122 (4) 717-720.

FDA. 1998: Food labeling: warning and notice statement; labeling of juice products; proposed rules. Federal Register 63: 20449-86.

Goverd, K.A., Beech, F.W., Hobbs, R.P., and Shannon, R. 1979. The occurrence and survival of coliforms and salmonellas in apple juice and cider. J. Appl. Bacteriol., 46: 521-530.

International Commission on Microbiological Specifications for Foods. 1996. Microorganisms in Foods. Chap. 14 Salmonellae pp. 217-264.

Mead, P. S., Slutsker, L., Dietz, V., McCaig, L.F., Bresee, J.S., Shapiro, C., Griffin, P. M., and Tauxe, R. V. 1999. Food-related illness and death in the United States. Emerg. Inf. Dis. 5 (5): 606-625.

Shapiro, R, Ackers, M., Lance, S, Rabbani, M., Schaefer, L., Daughter, J.,Thelen, C., and Swerdlow, D. 1999. Salmonella Thompson associated with improper handling of roast beef at a restaurant in Sioux Falls, South Dakota. J. Food Prot. 62 (2): 118-122.

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SALMONELLA HACCP

Salmonella spp. – Process Hazard Analysis The Animal Source Animals become infected with Salmonella by consuming contaminated feed and by environmental contact when they lie in fecal material. Rodents and birds defecate on animal and poultry feed and can be an initial source of Salmonella. Salmonella HACCP, then, really begins with the feed. Ideally, animal feed should be pasteurized so that the animals will not be infected. However, the cost of this process with no apparent return on investments has meant minimal and only academic interest by feed manufacturers.

Animals spread infection to other animals while in transit or in pens. In fact, during transit when the animals are in stress, Salmonella can increase 10- to 100-fold in the animals' intestines. Chickens and turkeys that are infected with Salmonella bring these organisms into poultry processing plants. A contaminated carcass or fecal material then contaminates equipment and/or workers' hands. Salmonella can be transferred from equipment surfaces and workers' hands to other carcasses or to processed foods. As plants process even greater volumes of animals and poultry, the likelihood becomes greater that an infected carcass will cross-contaminate other finished products. Once introduced into a plant, Salmonella can survive on equipment or in the plant environment, and can subsequently contaminate other products until adequate cleaning and sanitizing measures (normally, only every 4 hours) are applied.

Salmonella enteritidis has been found to be present within the yolks of intact Grade A shell eggs. Laying hens infected with S. enteritidis can transmit the microorganism to the yolk before the shell of the egg is formed in the ovaries. The U.S. government standards now recommend that shell eggs be kept below 45°F (7.2°C). If contaminated Grade A shell eggs are held at 60° (15.6°C) for 2 weeks, they can become very hazardous.

In order to control this problem, flocks of chickens must be raised under conditions which prevent S. enteritidis infection and hence can be certified Salmonella-free.

The FDA Food Code recommends cooking shell eggs until a temperature of 145°F (63°C) for 15 seconds is reached throughout the egg.

Recent processing methods have been developed for pasteurizing shell eggs, which assure the destruction of Salmoella enteritidis in the intact egg (Hou et al., 1996). Only pasteurized egg products should be used to prepare eggs and egg products for people at risk (e.g., rest homes and hospitals).

Means of Contamination The transmission of Salmonella and the occurrence of outbreaks are influenced by food processing, food distribution, and foodservice operations. Animal feeds contain rendered animal by-products that are often contaminated with Salmonella. This feed then contaminates the intestine of animals that eat it. When the animal is slaughtered, there is a high risk of contamination of raw meat. Salmonella can also survive in litter, soil, animal feces, trough water, and other substances in a farm environment. Operations where large numbers of animals are kept in confined areas contribute to the problem of animal-to-animal transmission.

Foods prepared by delicatessens and retail markets (e.g., salads, sandwiches, roast meats, barbecued poultry) may become cross-contaminated from knives and cutting boards with Salmonella from raw food products. Inadequate cooking, cross-contamination, and storage in warmers at hazardous temperatures of 80 to 114°F (26.7 to 45.6°C) that allow rapid growth of Salmonella spp. for more than 2 hours have led to outbreaks of salmonellosis.

Foods prepared in foodservice establishments are sometimes prepared a day or more before serving. This practice is labor efficient, but it decreases the food's quality and safety. If the food is allowed to be in the temperature range of 80 to 114°F (26.7 to 45.6°C) for more than an hour, a hazard that permits the rapid multiplication of Salmonella spp. will develop.

Improper sanitation practices, inadequate cooling and reheating, and unsafe cooking practices aggravate these problems.

Salmonella spp. enters foodservice establishments on raw animal products or in the feces and on the fingers of infected employees. Salmonella spp. grow when foods are mishandled, undercooked, or recontaminated after cooking and then allowed to remain at dangerous temperatures.

Importance of Hand Washing Persons with Salmonella on their fingers from fecal contamination can spread these bacterial cells onto salads or cold garnishes and cause illness. Salmonella can be isolated from fingertips 3 hours after contamination with 500 to 2,000 cells. One study showed that ham and corned beef became contaminated after being touched by persons whose hands had just 100 cells 15 minutes earlier, and had not been washed adequately. The study shows the potential for cross-contamination and emphasizes the need for vigorous hand washing using hand soap/detergent and flowing warm water after touching items that might be contaminated with Salmonella.

Food Distribution Problems With modern food distribution systems, widespread disease outbreaks can result before any attempt to recall a contaminated lot of food can be made. Contamination that results from an error in storage of a food that is later distributed can result in human illness thousands of miles from

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the contamination source and months after the contamination occurred.

References: Hou, H., Singh, R.K., Muriana, P.M., and Stadelman, W.J.

1996. Pasteurization of intact shell eggs. Food Microbiology. 13: 93-101.

International Commission on Microbiological Specifications for Foods. 1996. Microorganisms in Foods. Chap. 14 Salmonellae pp. 217-264.


Tauxe, R.V. 1991. Salmonella: a postmodern pathogen. J. Food Prot. 54: 563-568.

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SALMONELLA CONTROL -- TEMPERATURE

Salmonella spp. – Process Critical Controls Salmonella Control The rate of growth of Salmonella is dependent on temperature, pH, salinity, water activity (aw), and nutrient content of the surrounding medium. By manipulating any one or a combination of these factors, the growth of these bacteria in food can be controlled.

Generation Time Although some strains of salmonellae may grow at lower temperatures, it is generally accepted that the growth of most Salmonella spp is between 41 and 115°F (5 and 46°C).

Table 4-10 lists predicted average generation times (times necessary for doubling of Salmonella in foods).

Table 4-10 Predicted Average Generation Times for Salmonella in

Foods*

Temperature °F (°C)

Time

41 (5) little or no growth 45 (7.2) 23.0 hours 50 (10) 11.5 hours

60 (15.6) 4.5 hours 70 (21.1) 2.5 hours 80 (26.7) 1.5 hours 90 (32.2) 1.0 hours

50.0 minutes 100 (37.8) 45.0 minutes 115 (46.1) no growth

95 (35)

* Adapted from data of Snyder, O.P. (1998).

For example, four (4) hours at 100°F (37.8°C) with a generation time of 45 minutes allows Salmonella to multiply about 5 times. If there were 10 Salmonella in a portion of food at time zero, there will be approximately 320, 4 hours later. This is a hazardous level for a few people. If the same food is held at 60°F (15.6°C) (with 4.5-hour generation times) for 12 hours, there will be a 3-generation increase in salmonellae which is a very low risk. The upper temperature limit for growth is approximately 114°F (45.6°C) (Angelotti et al., 1961). Salmonella spp. have been shown to survive

freezing and freezer storage. The strains, which have a tendency to be more susceptible to the cold and dry environment, are also low-incidence strains. The ability of certain serotypes to survive may be a factor in their higher incidence of causing salmonellosis.

Heat Resistance The cells are not heat resistant and at 120°F (48.9°C) they are inactivated very slowly. Neither spores nor toxins are formed, so heating food to a center temperature of 165°F (73.9°C) for 3 minutes will reduce any population of Salmonella at a high water activity to an undetectable level.

Heat processes have been designed to destroy Salmonella in various products. Pasteurization of eggs is an example. Regulations differ among countries and for each egg product, but they usually require heating liquid eggs to a temperature of 140°F (60°C) or higher and holding them at these temperatures for 2 to 4 minutes. Present standards for pasteurization of milk are: 145°F (62.8°C) for 30 minutes or 161°F (71.7°C) for 15 seconds inactivate more than 1010 Salmonella per gram of milk.

Tables 4-11 and 4-12 indicate the times necessary to cause a 107 Salmonella reduction in chicken ala king, custard, and beef roasts. Products such as dried egg powder, chocolate candy, and custards because of their lower water activity, require temperatures at least 10°F (5.5°C) higher or times that are 10 times longer at a specified temperature in order to destroy Salmonella.

Table 4-11 Time Required for a 107 Destruction of Salmonella

manhattan in Chicken a la King and Custard*


Chicken a la king(min.)

Custard (min.)

130 (54.4) 36 100 135 (57.2) 10.5 44 140 (60) 3.0 19

145 (62.8) 0.9 8.1 150 (65.5) 0.3 3.5

*Adapted from data of Angeloti et al. (1961).

Growth in ideal conditions without competition from other organisms can begin with cross-contamination from Salmonella spp. on a cutting board that was used to cut raw chicken. If cooked meat or hard cooked eggs are subsequently cut on that board, these products will become contaminated. When the contaminated meat and eggs are used to prepare a salad or sandwiches, the population can be large enough to cause a foodborne illness.

Precooked roast beef was a source of salmonellosis in many states until the USDA instituted regulations in 1977. These regulations required that raw beef be cooked to a uniform temperature that provides a 107 reduction (see Table 4-12). USDA guidelines now recommend a 106.5 reduction.. Since these regulations/guidelines were adopted by food processors, the number of outbreaks of salmonellosis due to contaminated precooked beef has decreased.

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Table 4-12 Time Required for a 107 Salmonella Serotypes in 10-lb. or Larger Cuts of Beef* Compared with a 106.5 Destruction of

Salmonella**

Temperature ºF (ºC)

Time, 107

Time, 106.5

130 (54.4) 121.1 min. 112 min 135 (57.2) 37.0 min. 140 (60) 12.1 min. 11.2 min

144 (62.2) 5 150 (65.5) 1.21 min

(72.6 sec.) 1.1min. (67 sec.)

160 (71.1) 0.121 min. (7.26 sec.)

0.11 min. (6.7 sec.)

*Adapted from data of Goodfellow and Brown (1978). ** USDA FSIS. 2001. Control It is essential to prevent the multiplication of Salmonella spp. in food products. It is even more critical to prevent the presence of Salmonella spp. in foods that are high in fat. These foods (e.g., cheese, chocolate) provide a protective coating for the organism from the stomach acids. Therefore, fewer organisms are needed to cause illness. After foods are processed and prepared:

The FDA Food Code recommends cooling potentially hazardous food to 41°F (5°C) within 6 hours [§3-501.14: from 135 to 70°F (57.2 to 21°C) within 2 hours followed by cooling to 41°F (5°C) or below within a total time of 6 hours]. USDA Guidelines recommend cooling food, within 90 minutes after cooking, from 120 to 55°F within 6 hours, followed by further cooling to 40°F (no time limit) before boxing.

•

•

•

Holding food at a temperature above 114°F (45.6°C) exceeds the upper limit for Salmonella growth. [FDA Food Code recommends holding hot foods above 135°F (57.2°C)]. Post-process contamination of food must be prevented. This can be achieved by:

1. Training personnel to use frequent and correct hand

washing and food handling practices. 2. Using sanitary food handling procedures that prevent

cross-contamination. This includes preparation of raw foods, particularly meat and poultry in separate areas or with separate sanitized equipment in order to prevent transfer of this bacteria to cold or pre-cooked food products that will receive no further heating.

3. Monitoring the environment, the product during processing, and the finished product for Salmonella.

References: Angelotti, R., Foter, M.J., and Lewis, K.H. 1961. Time

Temperature effects on Salmonella and Staphylococci in foods. lll. Thermal death time studies. Appl. Microbiol. 9: 308-315.

Angelotti, R. 1977. Minimum cooking requirements for cooked beef roasts. Fed. Reg. 42: 44217-44218.

Bailey, J. S., and Maurer, J. J. 2001. Chapter 8. Salmonella Species. In Food Microbiology. Fundamentals and Frontiers. Doyle, M. P., Beuchat, L. R., and Montville, T. J. eds. pp, 141-178. American Society of Microbiology. Washington, D. C.

Goodfellow, S.J. and Brown, W.L. 1978. Fate of Salmonella inoculated into beef for cooking. J. Food Prot. 41: 598-605.


Snyder, O. P. 1998. Updated guidelines for use of time and temperature specifications for holding and storing food in retail food operations. Dairy Food Environ. Sanit. 18 (9): 574-579.

USDA FSIS. 2001. Draft compliance guidelines for ready-to-eat meat and poultry products. http://www.fsis.usda.gov/OPPDE/rdad/FRPubs/RTEGuide.pdf.

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http://www.fsis.usda.gov/OPPDE/rdad/FRPubs/RTEGuide.pdf


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• Grows best in small amount of air(oxygen)

• Grows between 86 and 113ºF• Survives chilling and freezing

temperatures• Source is infected animals, birds,

reptiles, and people• Common contaminant of raw foods of animal origin

(poultry, pork, raw milk)• Vegetative cells multiply in intestinal tract to cause illness• Infective dose = 400 to 500 cells in a portion of food• Vegetative cells killed by cooking1118

CHARACTERISTICSOF CAMPYLOBACTER JEJUNI

Campylobacter jejuni – Characteristics

Bacterial Characteristics Campylobacter jejuni is a gram-negative, slender, curved to spiral rod that is motile by means of a single polar flagellum. It is relatively fragile and sensitive to environmental stresses of more than 21% oxygen, drying, heating, sanitizers, and acidic conditions. These bacteria can survive refrigeration and freezing temperatures for a limited period of time.

Source Campylobacter jejuni is now recognized as a common cause of gastroenteritis in humans. It is commonly found as a pathogen in cattle, sheep, fowl, swine, and rodents. Incidents in which C. jejuni has been isolated as causing illness have resulted from the consumption of raw milk, undercooked poultry and pork. Campylobacter spp. can be spread by a contaminated water supply, and is carried by common household pets (particularly cats and dogs in poor health).

The presence of C. jejuni is high in fresh meat and may be as high as 100% in fresh poultry. The numbers of CFU (colony forming units) may vary from 10,000 CFU on a chicken wing to less than 1 CFU/cm2 in raw pork and 1 to 10 CFU/cm2 in raw beef (Genigeorgis, 1986).

Growth Conditions Temperature. In 1981, Doyle et al. reported the temperature range for growth of C. fetus subsp. jejuni as 90 to 113°F (32 to 45°C). The optimum range for growth seems to be 107.6 to 113°F (42 to 45°C). Doyle (1988) stated that C. jejuni will not grow below 86°F (30°C).

Ordinary cooking, which destroys Salmonella spp., also destroys Campylobacter spp. Doyle (1984) reported that heating meat to 140°F (60°C) and holding it at this temperature is sufficient to destroy any Campylobacter present.

pH. The pH range for growth is 5.0 to 8.0.

Atmosphere. The organism is microaerophilic and requires an atmosphere of reduced oxygen for growth. Optimal growth conditions require 5 to 10% oxygen and 2 to 10% carbon dioxide. Because of its sensitivity to air and the relatively high temperature required for growth, growth of C. jejuni in foods is unlikely under ordinary conditions of food handling. The

minimum water activity (aw) for growth of C. jejuni in foods is 0.987

Salt tolerance. At 107.6°F (42°C) C. jejuni will grow in 1.5% table salt (sodium chloride, NaCl) and 0.5% NaCl, but not in 2% NaCl.

Survival. The organism does not grow in milk, but will survive 22 days at refrigeration temperatures of 39.2°F (4°C). If milk is held at 77°F (25°C), destruction of the microorganism occurs within 3 days. C. jejuni can survive on raw chicken held at -4°F (-20°C) for more than 64 days (Oosterom et al., 1983).

Infective Dose A pathogenic dose is usually given as ranging from 106 to as few as 400 to 500 organisms (Walker et al., 1986; FDA, 1993). Host susceptibility seems to dictate infectious dose. The pathogenic mechanisms of C. jejuni are still not completely understood. It does produce a heat-labile toxin that may cause diarrhea. It may also be an invasive organism (FDA, 1993).

Symptoms The symptoms of illness caused by C. jejuni (Campylobacteriosis) are similar to those caused by other enteric pathogens such as Salmonella spp., Shigella spp., and Escherichia coli. Stool cultures are used to provide positive identification.

Symptoms may be mild to quite severe and appear 2 to 5 days after ingestion of contaminated food or water. In severe cases, ingestion of C. jejuni produces severe, even bloody, diarrhea with fever, nausea, and severe abdominal pain. Blood in stools may continue for 2 to 3 days after the symptoms are first observed.

Interestingly, children seem less seriously affected than adults who may appear to have ulcerative colitis. The illness may linger 1 to 2 weeks in all ages. Occasionally there may be a relapse characterized by a recurrence of abdominal pain and mild to severe gastroenteritis and bloody diarrhea which may last for several weeks.

Complications of infection by C. jejuni may include abdominal pain resulting in unnecessary appendectomies, reactive arthritis, Reiter's syndrome, and Guillain-Barré syndrome.

Incidence Campylobacter jejuni is the most common bacterial cause of diarrheal illness in the U.S. Mead et al. (1999), estimated an annual incidence of 1,900,000 cases of Campylobacter illness in the U.S. resulting in 10,500 hospitalizations and 100 deaths. The annual incidence as estimated by the FDA (1993) is 2 to 4 million cases a year. Roberts and van Ravenswaay, 1989 estimated the annual cost of campylobacteriosis at about 1 billion dollars.

OUTBREAK EXAMPLE I. The following example appeared in MMWR 35(19):311-312, 1986.

Campylobacter Associated with Raw Milk Provided on a Dairy Tour - California. On October 3, 1985, students and teachers from northern California and some of their family members made a field trip to a San Joaquin County dairy. Of

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the 50 attendees from whom information was available, 23 (46%) became ill with Campylobacter jejuni infection.

Twenty-three (59%) of the 39 attendees who drank raw milk, and none of the 11 who did not drink it, became ill. Included among the cases was an infant who had been almost exclusively breast-fed and became ill after drinking a bottle filled with raw milk at the dairy. In addition, secondary cases occurred in 2 women who had not visited the dairy but who tended an infant who drank raw milk and developed Campylobacter gastroenteritis. Stool cultures from 1 asymptomatic and 8 ill persons grew C. jejuni.

Of the 23 ill field-trip attendants, 96% reported diarrhea; 35%, abdominal cramps; 35%, fever; 26%, vomiting; and 22%, bloody diarrhea. Incubation periods ranged from 1 day to 10 days, but were 3 or 4 days in most cases. Symptoms most commonly lasted 5 days.

Numerous outbreaks of enteric diseases have occurred among school children given raw milk while on field trips to dairies in the United States. As a result, in January 1985, the U.S. Food and Drug Administration (FDA) issued a "milk advisory" to all state school officers recommending that children not be permitted to sample raw milk on such visits.

Healthy lactating cows can carry C. jejuni in the intestinal tract, providing an extrinsic source of contamination. Since culture of diarrheal stools for C. jejuni became common, many raw milk-associated Campylobacter outbreaks involving thousands of cases have been reported.

Milk is an excellent vehicle for infection, because its fat content protects pathogens from gastric acid and because, being fluid, it has a relatively short gastric transit time. Present technology cannot produce raw milk that can be assured to be free of pathogens. Milk must be pasteurized to insure the destruction of Campylobacter jejuni. In Scotland, the incidence of illness due to C. jejuni has decreased markedly since 1983 when the sale of raw milk was banned.

OUTBREAK EXAMPLE II. The following example appeared in a Minnesota Department of Health 1998 Gastroenteritis Outbreak Summary.

Campylobacteriosis Associated with Eating Lettuce in a Restaurant. An investigation was taken of a foodborne illness outbreak involving 152 people that occurred when three separate groups of individuals developed gastrointestinal illness days after eating at a restaurant in June 1998. All 152 cases reported diarrheal illness that lasted from 2 to 20 days. One hundred-nineteen (78%) reported fever, 37 (24%) reported vomiting, and 22 (14%) reported bloody stools. The median incubation period was 52.5 hours. The median duration of illness was 6 days. Forty-two (69%) of the 61 stool specimens tested positive for Campylobacter jejuni. Salads and sandwiches containing lettuce were significantly associated with illness. The investigation identified several possible ways for the cross-contamination of raw chicken and produce items in various preparation procedures. These deficiencies included poor handling and storage of fresh vegetables, raw meat, and poultry products.

References: Adams, M. R. and Moss, M. O. 1995. Food Microbiology.

The Royal Society of Chemistry. Cambridge, U.K. Altekruse, S.F., Stern, N.J., Fields, P. L., and Swerdlow, D. L.

1999. Campylobacter jejuni - An emerging foodborne pathogen. Emerg. Infect. Dis. 5 (1):28-35.

Chin, J. ed. 2000. Control of Communicable Diseases in Man. American Public Health Assoc., Washington, D.C.

Doyle, M.P. 1984 Campylobacter in foods. Chapt. 14 in Campylobacter Infections in Man and Animals. Butzler, J.P. ed. CRC Press, Boca Raton, FL.

Doyle, M.P. 1988. Campylobacter jejuni. Food Technol. 42(4): 187.

Doyle, M.P. and Roman, D.J. 1981 Growth and survival of Campylobacter fetus subsp. jejuni as a function of temperature and pH. J. Food Protect. 44(8): 596-601.

FDA, 1993. HACCP. Regulatory Food Applications in Retail Food Establishments. Dept. of Health and Human Services. Division of Human Resource Development, HFC-60; Rockville, MD.


Namchamkin, I. 2001. Campylobacter jejuni. In Food Microbiology. Fundamentals and Frontiers, 2nd edition. Doyle, M. P., Beuchat, L. R., and Montville, T. J. eds. American Society of Microbiology. Washington, D. C. pp.159-161.

National Advisory Committee on Microbiological Criteria for Foods. 1995. Campylobacter jejuni/coli. Dairy, Food and Environmental Sanitation 15 (3): 133-153.

Oosterom, J., DeWilde, G.J.A., DeBoer,E., DeBlaauw, L.H., and Karman, H. 1983. Survival of Campylobacter jejuni during poultry processing and pig slaughtering. J. Food Protect. 46(8): 702-706.

Roberts, T and van Ravenswaay, E. 1989. The economics of safe guarding the U.S. Food Supply. USDA Ag. Info. Bulletin No. 566: 1-6.

Stern, N. J. and Kazmi, S.U. 1989. Campylobacter jejuni. In Foodborne Bacterial Pathogens. Doyle, M.P., ed. Marcel Dekker, Inc., New York, NY.

Walker, R.I., Caldwell, M.B., Lee, E.C., Guerry, P., Trust, T.J., and Ruiz-Palacios, G.M. 1986. Pathophysiology of campylobacter enteritis. Microbiol. Rev. 50 81-94.

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CAMPYLOBACTER JEJUNI HACCP

Campylobacter jejuni – Process Hazard

Analysis and Critical Controls Transmission Infected humans and animals excrete the organisms in their feces. High numbers of this pathogen (106 per gram) are passed in the diarrheal stools of infected individuals. The transmission to humans may be by direct contact with infected people, animals or poultry; through contaminated carcasses and contaminated food and water. This means that cross-contamination on a cutting board or from a contaminated knife can create an instant hazard in another food that is prepared on that same cutting board or knife if that food is not heated sufficiently.

Foods most often implicated are poultry products, unpasteurized milk, meat and eggs, and uncooked foods such as salads and sandwiches that have been contaminated by meat or poultry products, by an infected food handler, or by untreated sewage.

Poultry is a common source of Campylobacter jejuni. Heavily infected flocks of chickens can contaminate an entire slaughtering operation. The microorganism can be isolated from the scalding water, pickers, and chilling tanks. Contaminated raw products may then cross-contaminate utensils, work surfaces, and cutting boards in any area where food is prepared.

Control Methods to control the transmission of this microorganism include:

1. Good personal hygiene by food handlers with emphasis on frequent hand washing.

2. Sanitary food handling procedures that prevent cross-contamination. This includes preparation of raw foods, particularly meat and poultry in separate areas or with separate sanitized equipment in order to prevent transfer of this bacteria to cold or pre-cooked food products that will receive no further heating.

3. Adequate cooking/pasteurization of meat and poultry to ensure the destruction of the microorganism.

4. The FDA recommends cooling potentially hazardous food to 41°F in less than 6 hours (e.g., from 135 to 70°F (57.2 to 21°C) within 2 hours; followed by cooling to

41°F (5°C) or below within a total time of 6 hours or less.]

5. USDA Guidelines recommend continuously cooling food, within 90 minutes after cooking, from 120 to 55°F (48.9 to 12.8ºC) within 6 hours, followed by further cooling to 40°F (4.4ºC) (no time limit) before boxing.

6. Avoid consumption of unpasteurized milk and dairy products.

While microbiological criteria may not be applicable, surveys to ascertain the incidence of this organism in the general food supply should be encouraged. Investigations of foodborne gastroenteritis outbreaks should include examination of suspect food for the presence of C. jejuni. Methods for detecting C. jejuni in foods are now available.

References: Archer, D.L. and Young, F. L. 1988. Contemporary Issues:

Diseases with a food vector. Clin. Microbiol. Rev. 1(4): 377-398.

Franco, D.A. 1989. Campylobacteriosis. J. Environ. Health 52(2): 88-91.

National Advisory Committee on Microbiological Criteria for Foods. 1995. Campylobacter jejuni/coli. Dairy, Food and Environmental Sanitation 15 (3): 133-153.

Stern, N. J. and Kazmi, S.U. 1989. Campylobacter jejuni. In Foodborne Bacterial Pathogens. Doyle, M.P., ed. Marcel Dekker, Inc., New York, NY.

USDA FSIS. 2001. Draft compliance guidelines for ready-to-eat meat and poultry products. http://www.fsis.usda.gov/OPPDE/rdad/FRPubs/RTEGuide.pdf

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• Grows with and without air• Grows between 29.3 and 111ºF• Survives freezing temperatures• Source is infected animals,

shellfish, and people• Found in raw milk, pork, water• Vegetative cells multiply in intestinal tract to cause illness

that may simulate appendicitis• 3.9x109 cells in a portion of food can cause illness• Vegetative cells killed by cooking / pasteurization

1117

CHARACTERISTICSOF YERSINIA ENTEROCOLITICA

Yersinia enterocolitica –

Characteristics Bacterial Characteristics Yersinia enterocolitica is a gram-negative rod that may arrange itself singly or in short chains or heaps. Cultures grown at 77°F (25°C) show flagella and are motile, while those grown at 98°F (37°C) show no flagella and are not motile. It is aerobic and may be facultatively anaerobic.

Pathogenic Y. enterocolitica is not often encountered. Most virulent forms of Y. enterocolitica are of the O serotype (O3; O5,27; O8; and O9). However, serotype alone does not determine the virulence of the microorganism. The factor that causes the virulence of Y. enterocolitica is thought to be mediated by plasmids (self-replicating, extrachromosomal, circular DNA molecules).

Sources Yersinia enterocolitica is ubiquitous throughout the animal world. Yersinia enterocolitica is found in meat, especially pork, in oysters and mussels, and in milk and drinking water. Pathogenic strains are principally carried by pigs (Stern and Pierson, 1979).

Growth Conditions Growth temperatures range from 29.3 to 111°F (-1.5 to 44°C) but best growth occurs at 90 to 94°F (32 to 34°C). The organism is able to multiply at low temperatures under refrigeration. It is capable of multiplying in vacuum packaged roast beef at 29.3°F (-1.5°C) (Hudson et al., 1994). Table 4-13 lists the average generation times for Y. enterocolitica in foods.

The organism grows at pH 4.6-9.0. A pH of 7.0-8.0 is optimal for growth. A pH of less than 4.4 or above 9.6 is bacteriocidal. At 37°F and 77°F (3°C and 25°C), 7% table salt (sodium chloride, NaCl) is inhibitory, but at 37°F (3°C) in 5% NaCl, growth is observed.

Extensive reductions of the Y. enterocolitica occur during frozen storage, but there will still be survivors. Hanna et al. (1977) found that there was a 2.9 to 4.0 log reduction in the counts when beef sirloin tip roasts were experimentally inoculated with 106 to 107 cells per gram and stored at 0 to -4°F (-18 to -20°C) for 28 days.

Table 4-13 Predicted Generation Times for Yersinia enterocolitica in

Foods*


Generation Time

32 (0) 2.5 days 41 (5) 13.5 hours

45 (7.2) 8.9 hours 50 (10.0) 5.8 hours 60 (15.6) 3.0 hours 70 (21.1) 1.9 hours 80 (26.7) 1.2 hours 90 (32.2) 50 minutes 95 (35.0) 45 minutes

111 (43.9) no growth

* Adapted from data of Snyder, O.P. (1998). Yersinia enterocolitica is destroyed by standard pasteurization times and temperatures. There have been incidents when it has been found in pasteurized milk, but this is thought to be due to cross-contamination after pasteurization.

Symptoms Yersinia enterocolitica is the cause of yersiniosis, a foodborne infection. The incubation time is 24 to 36 hours and longer. The symptoms of the illness are abdominal pain, fever, headache, malaise, nausea, vomiting, and diarrhea. The severe abdominal pain caused by this illness has led to a misdiagnosis of appendicitis. Several cases have resulted in unnecessary appendectomies, especially in children.

Complications from yersiniosis sometimes occur. These include: arthritis, mesenteric lymphadenitis, terminal ileitis, erythema nodosom, endocarditis, septicemia, and meningitis. It has sometimes been misdiagnosed as Crohn's disease. The major complication is unnecessary appendectomies, since one of the main symptoms is abdominal pain of the lower right side.

Infective Dose The infective dose as defined by Moustafa et al. (1983) is 3.9 x 109 organisms or 2 x 107 in 200 grams of cheese. This is based on a single volunteer study and the infective dose may be much lower.

Methods of Recovery Methods of recovering Y. enterocolitica from foods have improved in recent years. However, no single method is suitable for recovery of all types of this species from various foods. Since not all strains are pathogenic, isolates must be tested for pathogenicity. Primary and secondary or selective enrichment procedures, followed by determination of biochemical and serological characteristics of cultural isolates, are required. Isolation and confirmation may require 2 to 3 weeks.

Incidence The illness has been more prevalent in Japan and Europe than in the United States and Canada. The first outbreak reported to CDC in which foodborne yersiniosis transmission was documented in the United States occurred in 1976 among school children in Oneida County, New York. Chocolate milk

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was the indicted food. Yersinia had been suspected of causing previous similar foodborne illness outbreaks but this could not be clearly documented.

In the above-mentioned outbreak of yersiniosis due to chocolate milk, neither the chocolate syrup nor the milk (pasteurized) could be implicated, but the mixture was. In the dairy plant, the chocolate syrup was manually added to a large open vat of pasteurized milk, and the mixture was not repasteurized before being placed in cardboard (1/2-pint) cartons. The milk was distributed to the schools in an unrefrigerated truck.

Water can be a source of Y. enterocolitica. Water used in the preparation of tofu was identified as the source of the microorganism in an outbreak. Another episode of yersiniosis occurred when skiers in Montana consumed water from a mountain stream.

An outbreak of yersiniosis occurred in Arkansas, Mississippi, and Tennessee in 1982. (172 people ill from pasteurized milk). In this incident, milk crates had been contaminated with pig feces from a farm that was receiving returned milk from a local dairy plant.

Another incident occurred the same year in the state of Washington. It was determined that yersiniosis was due to consumption of tofu (soybean curd) which had been produced in a processing facility using non-chlorinated water.

The concern at this time is post-pasteurization contamination of milk with pathogenic or virulent strains of Yersinia. Raw or inadequately cooked seafood, vacuum-packaged meat, and processed products handled by infected workers can be a potential source of Y. enterocolitica.

The estimated annual incidence of Y. enterocolitica in the U.S. is over 86,000 cases, resulting in 2 to 3 fatalities (Mead et al., 1999).


The Royal Society of Chemistry. Cambridge, U.K. Doyle, M.P. 1988. Yersinia enterocolitica. Food Technol.

42(4):188. Hanna, M.O., Stewart, J.C., Zink, D.L., Carpenter, Z.L., and

Vanderzant, C. 1977. Development of Yersinia entercolitica on raw and cooked beef or pork at different temperatures. J. Food Sci. 42(5): 1180-1184.

Hanna, M.O., Stewart, J.C., Carpenter, Z.I., and Vanderzant, C. 1977b. Effect of heating, freezing, and pH on Yersinia enterocolitica-like organisms from meat. J. of Food Protect. 40: 689-692.

Hudson, J.A., Mott, S.J., and Penney, N. 1994. Growth of Listeria monocytogenes, Aeromonas hydrophila, Yersinia enterocolitica on vacuum and saturated carbon dioxide controlled atmosphere-packaged sliced roast beef. J. Food Protect. 57 (3): 204-208.


Moustafa, M.K., Ahmad, A. A-H., and Marth, E. 1983. Behavior of virulent Yersinia enterolitica during

manufacture and storage of colby-like cheese. J. Food Protect. 46:318-320. In

Robins-Browne, R.M. 2001. Yersinia enterocolitica In Food Microbiology. Fundamentals and Frontiers, 2nd edition. Doyle, M. P., Beuchat, L. R., and Montville, T. J. eds. American Society of Microbiology. Washington, D. C. pp. 215-246.

Schiemann, D.A. 1989. Yersinia enterocolitica and Yersinia pseudotuberculosis. In Foodborne Bacterial Pathogens. Doyle, M.P., editor. Marcel Dekker, Inc., New York, NY.

Snyder, O. P. 1998. Updated guidelines for use of time and temperature specifications for holding and storing food in retail food operations. Dairy Food Environ. Sanitation 18 (9): 574-579.

Stern, N.J. and Pierson, M.D. 1979. Yersinia enterocolitica: A review of the psychrotrophic water and foodborne pathogen. J. Food Sci. (44) 1736-1741.

Sutherland, J.P. and Varnham, A.H. 1977. Methods of isolation and potential importance of Yersinia enterocolitica in foods stored at low temperatures. J. Appl. Bacteriol. 43:13-14.

Swaminathan, B., Harmon, M.C., and Mehlman, I.J. 1982. A review - Yersinia enterocolitica. J. Appl. Bacteriol. 52:151-183.

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YERSINIA ENTEROCOLITICA HACCP

Yersinia enterocolitica – Process Hazard

Analysis and Critical Controls Transmission Although frequently found in swine and other food animals and often reported as causing illness in humans in other countries, relatively few documented outbreaks of foodborne illness due to Yersinia enterocolitica have been reported in the United States. The low incidence of this foodborne illness may be due to the relatively high number of microorganisms of a virulent strain needed for an infective dose. Incidents of yersiniosis have been due to contaminated chocolate milk, tofu (soybean curd) packed in contaminated water, contaminated pasteurized milk, and drinking water from an unsafe source. The major mode of transmission is food and water contaminated with animal feces (particularly swine) and urine.

Control Yersinia enterocolitica presents a special problem because it is psychrotrophic (can grow at refrigerator temperatures.) The introduction of Y. enterocolitica into refrigerated foods, by cross-contamination and food handlers is very possible. Not all types of Yersinia are virulent and accurate methods of detecting virulent strains have yet to be determined.

In order to prevent an outbreak of yersiniosis, food service establishments should:

1. Use only pasteurized milk. 2. Buy food products from suppliers who certify the

microbiological quality of their products and use safety assured manufacturing practices.

3. Use care to prevent cross-contamination between raw products (particularly pork products) and prepared, ready-to-eat foods.

4. Use water and ice supplied from a safe water supply. 5. Mandate employee hand washing procedures after raw

products are handled (particularly raw meats). 6. Use cold, ready-to-eat food stored at or below 41°F

(5°C) within 7 days. 7. Clean and sanitize all utensils before starting a food task

in order to prevent cross-contamination. 8. Cook food according to the Salmonella pasteurization

standard that will destroy Y. enterocolitica.


The Royal Society of Chemistry. Cambridge, U.K. Doyle, M.P. 1988. Yersinia enterocolitica. Food Technol.

42(4):188. Mossel, D.A.A., Corry, J. E., Struijk, C. B., and Baird, R.


Schiemann, D.A. 1989. Yersinia enterocolitica and Yersinia pseudotuberculosis. In Foodborne Bacterial Pathogens. Doyle, M.P., editor. Marcel Dekker, Inc., New York, NY

Snyder, O.P. 1989. Hazard Analysis and Critical Control Points Manual. Hospitality Institute of Technology and Management. St. Paul, MN.

Swaminathan, B., Harmon, M.C., and Mehlman, I.J. 1982. A review - Yersinia enterocolitica. J. Appl. Bacteriol. 52:151-183.

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