Foodborne Pathogens: Bacteria
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Foodborne Pathogens: Bacteria
March 2nd, 2010
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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
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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
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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
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Escherichia coli• Food risks• Beef• Ground beef is higher risk
(contamination during processing)• Vegetables that become
contaminated by fecal matter (spinach!)
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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
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Salmonella
• Food risks• Eggs• Chicken• Unpasteurized milk• Has been linked to processed foods
as well
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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
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Listeria• Gram positive rod
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Listeria• Food risks• Unpasteurized milk• Raw milk soft cheeses• Deli meats
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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
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Staphylococcus aureus
• Gram positive cocci• Distinguishing feature is a positive
coagulase (plasma coagulation) reaction
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Staphylococcus aureus
• Food risks• Custards• Sliced meats• Meat products
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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
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Botulism• Gram positive anaerobic rod• Toxin can be detected using
antibody assays• Bacteria may not be culturable in
suspect food
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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
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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