Foodborne Pathogens: Bacteria

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