1. Foodborne Pathogens: Bacteria
March 2nd, 2010

2. Bacterial pathogens in food
Foodborne disease is likely underreported
Not all foodborne outbreaks are recognized
Causes can be difficult to pinpoint
Occur in all types of foods

3. Categories of foodborne disease
Diseases caused by ingestion of the organism and subsequent infection
E. coli O157:H7
Salmonella spp
Listeria monocytogenes
Campylobacter jejuni
Diseases caused by ingestion of toxins produced by bacteria in foods
Clostridium botulinum
Staphylococcus aureus

4. Escherichia coli Example: O157:H7
Belongs to the enterohemorrhagic group
Cattle are the major reservoir
Found in their intestinal tracts
Contamination during slaughter process
Major risk group is children: hemolytic uremic syndrome

5. Escherichia coli Food risks Beef
Ground beef is higher risk (contamination during processing)
Vegetables that become contaminated by fecal matter (spinach!)

6. Salmonella Diarrheal disease Fecal-oral route Species enterica
Many serogroups that cause foodborne disease
Distinct from typhoid fever
Typhoid fever can spread via food, but is rare in countries with advanced sanitation

7. Salmonella Food risks Eggs Chicken Unpasteurized milk
Has been linked to processed foods as well

8. Listeria Listeria monocytogenes
Often a mild disease, but can progress to meningitis and septicemia
High risk for pregnant women; can cause miscarriage
Bacteria has environmental reservoirs (soil, grains used as livestock feed)
Can survive and grow at refrigeration temperatures

9. Listeria
Gram positive rod

10. Listeria Food risks Unpasteurized milk Raw milk soft cheeses
Deli meats

11. Staphylococcus aureus
Disease is caused by the toxin produced by the bacteria
Foodborne intoxication
Bacteria produce the toxin while in the food
Onset is usually short time after eating
Toxin is fairly heat stable

12. Staphylococcus aureus
Gram positive cocci
Distinguishing feature is a positive coagulase (plasma coagulation) reaction

13. Staphylococcus aureus
Food risks
Custards
Sliced meats
Meat products

14. Botulism Clostridium botulinum Get into food, grow and produce toxin
Neurotoxin: causes descending paralysis
Can be fatal
Treated with antitoxin
Bacteria occur naturally in soil as spores
No person-to-person transmission

15. Botulism Gram positive anaerobic rod
Toxin can be detected using antibody assays
Bacteria may not be culturable in suspect food

16. Botulism Food risks Improperly processed low-acid canned foods
Low oxygen content
Toxin can be destroyed by heating, but improperly heated foods are at risk
Outbreaks associated with home canning

17. Control of foodborne bacteria
Food sanitation
Prevention of spread from ill food handlers
Handwashing
Sanitizing production environments
Prevention of cross-contamination from raw foods
Process control during food production
Adequate cooking and refrigeration
Pasteurization