Listeria Flashcards
What bacteria is Listeria related to and how are they different?
Bacillus but it doesn’t form spores
How many species does Listeria have?
6 but only one pathogen
What species of Listeria causes CNS infections and abortions in ruminants?
Listeria monocytogenes
What does Listeria look like on gram stain?
gram positive, small, fat rod, but commonly coccoid
What do colonies of Listeria monocytogenes look like?
relatively small colonies with narrow zone beta hemolysis
Is Listeria monocytogenes catalase positive or negative?
positive
Where does L. monocytogenes live?
in soil, plant material, and intestinal tracts especially of herbivores
At what pH does Listeria multiply?
pH 5.5 to 9.0
What pH does silage need to be below to prevent Listeria?
5
What is human listeriosis commonly due to?
food contamination: raw hotdogs, ice cream, milk, cheeses, organically grown lettuce
What kills Listeria in food?
proper pasteurization
What toxin does Listeria have?
listeriolysin O
What type of toxin is listeriolysin O?
cholesterol-binding
What is the function of listeriolysin O?
it destroys the phagosomal membrane and allows listeria to be a facultative intracellular parasite
How does infection of Listeria usually happen?
most animals and humans are exposed to Listeria but become infected due to bad silage or severely contaminated foods
What hosts are especially susceptible to Listeria?
immunosuppresed - pregnancy, stresses, and intercurrent diseases
What disease does Listeria cause in ruminants?
circling disease and abortions
What are the symptoms of circling disease?
meningoencephalitis, unilateral facial paralysis, fever, blindness, head pressing, and circling in the same direction
What does listeriosis cause?
septicemia in monogastrics and young ruminants
What immunization is possible for Listeria?
a live-attenuated vaccine (not available in US) that expresses cancer antigens
What treatment works for Listeria?
ampicillin, penicillin, and tetracycline
