Foodborne Pathogens: Bacteria
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Transcript of Foodborne Pathogens: Bacteria
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