The Listeria species of bacteria are routinely found in the environment. Listeria monocytogenes is common in the intestinal tracts of animals and humans. Animals, particularly cattle, can carry Listeria without appearing sick and shed the bacteria in their feces.
Sources of the organism:
- Intestinal tracts of animals and humans
- Contaminated water
- Soil
- Manure
Associated foods:
- Unpasteurized milk and milk products
- Soft cheeses
- Raw fruits and vegetables
- Ready to eat deli meats and salads
- Hot dogs
Microorganism characteristics: Gram positive rod shaped bacteria that thrives in anaerobic and microaerophilic conditions.
The Disease: Listeriosis is a potentially fatal disease which occurs most often in immunocompromised individuals and elderly. Pregnant women and their unborn fetus are at the greatest risk.
Symptoms include:
- Meningitis
- Spontaneous abortions and stillbirths
- Diarrhea
- Nausea
- Vomiting
- Fever
- Septicemia
- Encephalitis
Onset time:
- 2-21 days
Infective Dose:
- Small numbers (fewer than 1000 organisms) need to be consumed for symptoms of the illness to develop in a susceptible host.
Duration of symptoms:
- Variable
Control:
- Thoroughly cook foods.
- Use pasteurized milk.
- Proper sanitation of food contact surfaces and utensils.
- Thoroughly wash fresh fruits and vegetables.
- Prevent cross contamination.
- Because Listera monocytogenes grows slowly at refrigeration temperatures, refrigerated foods need to handled and stored properly. Observe "sell by" and "use by" dated on processed foods.
Sources:
About Listeria Infection, Centers for Disease Control and Prevention
Bad Bug Book, Foodborne Pathogenic Microorganisms and Natural Toxins. Second Edition., Food and Drug Administration (FDA)
Get the Facts about Listeria, U.S. Food and Drug Administration (FDA)
