Foodborne diseases

BacteriaFungiViruses

Reading Materials

Introduction to Foods and Food Science Department of Human Nutrition St.FX

chapter 4 pp. 446-454

Food borne diseases

Bacteria: Salmonella, Listeria, Staphylococcus, Bacillus, Campylobacter, Yersinia, Cl. perfringens, Shigella, E. Coli, Vibrio

Fungi: AspergillusViruses: Hepatitis A,

Norwalk virusParasites: Trichinella

spirallis, toxoplasma gondii,

Salmonellosis

Accounts for 40% foodborne diseases in USA

Often misdiagnosed as intestinal influenza

Incubation time: 6-48h (12-36h) Symptoms: diarrhea, abdominal

cramps, vomiting, fever which last 1-7 days.

Vehicles for Salmonella: beef, turkey, home-made ice cream, chicken, raw eggs.

Contributing factors: improper cooling, inadequate cooking, ingestion of contaminated raw food, cross contamination

Staphylococcal poisoning

Second most prevalent food borne disease.

Onset: 30 min - 8hSymptoms: nausea, vomiting,

abdominal pain, sweating, chills, weak pulse, shallow respiration, subnormal body temperature

Recovery 24-48hSufficient toxin present if more

than million cells present per g

Staphylococcal poisoning

Foods: meat and meat products, fish and fish products, milk and milk dairy products, ice creams, puddings, custards, cream filled bakery products

Staphylococci can tolerated 10-20% salt, 50-60% sugar, optimum temp. 35-37 C but may grow at 7C and as high as 47.5C

Enterotoxin stable under cooking

Listeriosis

Listeria monocytogenes. More than 40 animal species, but is also common in environment. Thus it can easily enter the processing plants (transported by humans, equipment, vehicles,shoes, ….). In a processing plant (typically cold and wet environment), Listeria can establish itself and persist for long periods of time.

Found in wide variety of raw and processed foods such as deli meats like turkey, ham and bologna, hot dogs served cold; seafood salads; refrigerated pates and meat spreads

Listeriosis has a long incubation time (7-60 days) -difficult pathogen to identification and tracing contaminated food.

Elderly, pregnant newborn and immune-compromised most susceptible.

Causes septicemia, abortion and encephalitis in humans

Control of Listeria

Sanitation Cooking & avoiding cross

contamination Addition of ingredients inhibiting

growth (lactate, diacetate, nisin) Application of processes inhibiting

growth during shelf life (freezing, steam heat or

hot water); Use of packaging reducing growth, dipping products)

Maintain refrigerator temperature at 4ºC or below.

Avoid cross-contamination Use ready-to-eat, refrigerated foods as

soon as possible. Discard RTE after 7 days if cold stored at 5º C and after 4 days if cold stored stored between 5ºC

and 7ºC

Clostridium perfringens poisoning

Results from eating food contaminated by Clostridium perfringens; in the small intestine, the bacterium releases a toxin that often causes diarrhea.

The gastroenteritis is usually mild and can cause abdominal pain, abdominal expansion (distention) from gas; sometimes severe diarrhea, dehydration, and a severe decrease in blood pressure (shock). No vomiting and no fever.

Symptoms usually begin 8 to 12 hours after consuming contaminated food (sometimes 6 to 24 hours).The illness is usually over within 24 hours of the onset of symptoms.

Spores of Clostridium survive cooking. When the temperature drops back to less than about 140 F degrees, the spores germinate and begin to multiply.

Escherichia coli

Factors affecting survival and growth

Temperature: 8-10 C minimum growth do not grow above 44 C

pH 5.5 -7.5 may survive in acidic foods for several

weeks i.e apple cider 2-3 days at 25 C but 10-31 days at 8 C; less sensitive to acids in stationary phase of growth.

Inhibitory effects of organic acids: acetic>lacticcitric

Water activity: can survive at refrigerated temperature for many weeks when dessicated

Antimicrobials- no increase resistance

Other complications:

Seizures, coma, stroke, colonic perforation, pancreatitis, hypertension.

Thrombotic thrombocytopenic purpura -resembles HUS, generally causes less renal damage, but causes central nervous system deterioration, seizures and strokes (adults)

Mycotoxins in foods

MycosesMycotoxicoses

Fungal flora associated with foods

Aspergillus- aflatoxins, ochratoxins

Fusarium-zealorenone, trichothecenes, fumonisins

Penicillum-ochratoxins, patulin

Claviceps purpurea-ergotamines (alkaloids; rye and wheat).

Remember that:

Molds grow at moisture lower than will support bacteria

Not all molds produce toxins. Mold may produce toxins under one

set of conditions but not produce them under other set of conditions.

It is impossible to tell by appearance, taste, smell which moldy foods have toxins.

Some foods may not carry visible evidence of toxins (flour, peanut butter as well as that come from animals fed with mycotoxins contaminated feeds.

Remember that:

Fungus is unable to penetrate the intact seed. Drought and other stresses encourage mold damage.

Mycotoxins are heat stableAntimicrobials (sodium bisulfate,

sorbate, propionate, nitrate) reduce production of mycotoxins

pepper, cinnamon, clover inhibits the formation of mycotoxins

In semi-solid (jams, cheese) and liquid foods mycotoxins may diffuse inside food product

Food processes and mycotoxins

Sorting and trimming- removal of contaminated material

Cleaning- only reduceMilling may redistribute but do

not destroyBrewing-mycotoxins can be

transferred from contaminated grain to beer. Some reduction during mashing, wort boiling and fermentation

Thermal processing-some reduction depends on method of cooking

Extrusion-only some reduction

Viruses causing food borne disease:

Hepatitis A, non-A, B and non-B

Norwalk virus

Rotavirus

Astrovirus

Calicivirus

Hepatitis A

Virus spreads by fecal-oral route. Contaminated foods and water are vectors. After ingestion virus multiplies within intestine epithelium, passes to blood stream and then attack liver. Onset: 2-6 weeks. Illness last 4-6 weeks, after which full recovery is usual, but some individuals experience relapses. Symptoms: malaise, anorexia, nausea, lethargy, jaundice, pale feces, dark urine and liver pain.

Norwalk or norwalk like viruses

Major cause of food or water-borne gastroenteritis. Transmitted through oral-fecal route (consumption of fecally contaminated food or water, person to person spread). During outbreaks: foodborne transmission in restaurants, Contamination of food by food handlers.

Onset: 24-48h, last about 48-72 hr. 10 viral particles sufficient to infect individual.

Symptoms: nausea, acute-vomiting, non-bloody diarrhea, abdominal cramps, nausea; self-limiting.

Correct handling of food, frequent hand-washing and sick leave reduce transmission of viruses.

Trichinella spirallis

Found in pigs, rats and 40 species of wild animals.

Symptoms: in first week transient gastrointestinal symptoms, later fever, edema around of eyes, muscle pains. Rash and respiratory symptoms may also be present. Severe cases- pneumonia, congestive failure, toxemia and encephalitis

Control: Heating to at least 137F, but to 170 F recommended, Freezing kills parasite but time depends on freezing temperature (-10F, 20 days)

Trichinella spirallis

Found in pigs, rats and 40 species of wild animals.

Symptoms: in first week transient gastrointestinal symptoms, later fever, edema around of eyes, muscle pains. Rash and respiratory symptoms may also be present. Severe cases- pneumonia, congestive failure, toxemia and encephalitis

Control: Heating to at least 137F, but to 170 F recommended, Freezing kills parasite but time depends on freezing temperature (-10F, 20 days)