Foodborne Pathogens: Bacteria March 2nd, 2010

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

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

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

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

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

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

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

Listeria Gram positive rod

Listeria Food risks Unpasteurized milk Raw milk soft cheeses Deli meats

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

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

Staphylococcus aureus Food risks Custards Sliced meats Meat products

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

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

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

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