Food Hygiene

MICROBIAL FOOD- BORNE PATHOGENS

Food HygieneDemo Lecture

College of Veterinary Medicine, University of the Philippines Los BanosBy Therese Marie A. Collantes, DVM, MS

I. Categories of microbial food-borne pathogensA. Causes invasive infectionB. Causes toxico-infectionC. Causes intoxication

II. Significant microbial food-borne pathogensA. Invasive Infection-Salmonella typhimuriumB. Toxico-infection-E. coli O157C. Intoxication-Staphylococcus aureus

III. Control and Prevention of microbial food-borne pathogens

Lecture Outline

Categories of microbial food-borne pathogensOrganism invades and penetrates intestinal mucosa

Invasive

infection

Organism produces harmful toxins in the intestinal tract

Toxico-

infection

Organisms produces toxins or metabolites in the ingested food

Intoxica-tion

•E.coli O157

•Vibrio cholerae

•Vibrio parahaemolyticus

•Clostridium perfingens

•Bacillus cereus (Diarrheal syndrome)

•Salmonella typhimurium

•Salmonella typhi

•Shigella

•Listeria monocytogenes

•Staphylococcus aureus

•Bacillus cereus (Emetic syndrome)

•Clostridium botulinum (infant botulism)

Integrated Food Safety and Veterinary Public Health (S. Buncic, 2006)

Invasive infection

SalmonellosisEtiologic Agent

Salmonella typhimurium

-Gram negative, motile rods-Incubation period 6-48 hours-Transmission by contaminated food

Signs and Symptoms

Mild fever, nausea, vomiting, headache, aching limbs, abdominal pain and diarrhea

Salmonella invade epithelial cells in the ileum and proliferate in the lamina propria.

Source, Reservoir◦ Poultry, eggs, meat, milk,

chocolate, coconut◦ Food contaminated with

feces◦ Raw or undercooked food

Invasive infectionSalmonellosis

EpidemiologyAbout 50 000 cases a year of salmonellosis in humans are reported annually in the United States.

Control of Salmonellosis◦ Cook food thoroughly.◦ Pasteurize milk and dairy products; avoid consumption of

unpasteurized products.◦ Prevent cross-contamination of heat-treated foods.◦ Avoid undercooked or raw eggs.◦ Store heat-treated foods at <4°C or >60°C to prevent

growth.◦ Reduce carriage of livestock by vaccinating or dosing with

antibiotics or probiotics. ◦ Exclude infected or carrier-status individuals from handling

food.◦ Control rodents and insects.◦ Dispose of sewage in a sanitary manner.

Invasive infectionSalmonellosis

Toxico-infectionE.coli O157:H7

Etiologic Agent

Escherichia coli O157:H7

-Gram-negative rod, non-sporing-Motile, facultative metabolism-Incubation period 3-8 days

Signs and Symptoms

Diarrhea, urinary tract infection and other extraintestinal infections.

Hemorrhagic colitis (HC), hemolytic uremic syndrome (HUS), thrombotic thrombocytopenic purpura

Colonoscopy findings showed friable, inflamed, and hemorrhagic mucosa


•Enterohemorrhagic Escherichia coli (EHEC):Attaches to colonic enterocytes and releases virulence factors, most commonly shiga-like toxins (Stx), which disrupt protein synthesis, leading to cell death and subsequent bloody diarrhea. Release of toxins can lead to systemic complications. E coli O157:H7 is the most commonly recognized EHEC.

Toxico-infectionE.coli O157 Source, Reservoir

◦ Shiga toxin (stx)- producing E. coli O157 are carried in the GIT of healthy livestock such as:

◦ Cattle, sheep, deer, goats, poultry, horses, dogs, rats, flies, birds and humans

◦ Spread may be person-to-person, food-borne, and animal-to-person

◦ Survives in refrigerated food (ground beef), livestock wastes and soil (up to 1 year)

Epidemiology◦ Escherichia coli O157:H7 causes

73,000 illnesses in the United States annually.

Epidemiology of Escherichia coli O157:H7 Outbreaks, United States, 1982–2002

Control of O157:H7◦ Use GHP and HACCP in meat production.◦ Cook meat thoroughly until >72°C in the centre, instantaneously.◦ Pasteurize juice and dairy products; don’t consume unpasteurized

products. ◦ Prevent cross-contamination of heat-treated foods.◦ Exclude infected individuals from handling foods.◦ Use only potable water in food production; consume only potable

water. ◦ Prevent young children from contacting livestock and farm

environments. ◦ Avoid eating in areas that could be contaminated with animal feces.

Wash hands thoroughly before eating. ◦ Do not use organic waste or fecally-contaminated water on ready-to-

eat crops. ◦ Control rodents, insects and birds.


IntoxicationStaphylo-enterotoxicosis

Etiologic Agent

Staphylococcus aureus

-Non-motile, facultatively anaerobic cocci-Incubation period 1-6 hours-Transmission by contaminated food

Signs and Symptoms

-Nausea, vomiting, abdominal cramps, diarrhea, sweating, headache and drop in body temperature. -CNS stimulation, triggering emetic center to induce vomiting


•Source, Reservoir

-Anterior nares of 50% of people, environmental contaminant-Poor hygiene amongst food handlers with skin infections, those carrying pathogen in their nostrils- Contaminated food such as cold, cooked and handled food, cream and custard-filled bakery products, cream-based desserts, milk, meat, canned fish, seafood and fermented sausages.


S. Aureus produces a range of enterotoxins in food: Enterotoxin A, B, C1, C2, C3, D, E, F.

Most human food-borne disease is caused by type A enterotoxin.

Control of Staphylo-enterotoxicosis◦ Use good personal hygiene practices when

handling food. ◦ People with skin infection should not handle food.◦ Use GHP when handling food.◦ Chill cooked food rapidly in small quantities. ◦ Store cooked or heat-treated foods at <4°C or

>60°C. ◦ Avoid extensive handling of foods.◦ Avoid delays between cooking and eating.


Microbial food-borne pathogens can be classified into three groups. ◦ Invasive infection◦ Toxico-infection◦ Intoxication

Good handling practices prevent the occurrence of food-borne illnesses. ◦ Control in animal population◦ Control during processing◦ Control in preparation of food

Summary

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Food Hygiene