All are true about listeria except-
Correct Answer: Characteristic tumbling motility at 37degC
Description: Ans. is 'c' i.e., Characteristic tumbling motility at 37degC o L monocytogenes is a gram positive 'coccobacillus9 (coccoid rod) with tendency to occur in chains.o It exhibits characteristic, slow, tumbling motility when grown at 25degC but at 3 7degC is non motile. This is because peritrichous flagella are produced by the bacillus optimally at 20-30degC but only scantily or not at all at 37degC.o It grows on oridinary media with in a temprature range of 1deg to 45degC.o Most cases of human disease are caused by serotypes l/2a, l/2b and 4b.o The organism can be found as a part of the gastrointestinal flora in healthy individuals.o Human disease due to L. monocytogenes generally occurs in the setting of pregnancy or immunosuppression.o Culture media used for isolation are blood agar, chocolate agar and PALCAM agar,o Listeria monocytogenes shows '"subtle' beta hemolysis on blood agar.Because of its motility, when inoculated in a tube (in liquid or semisolid medium), L monocytogenes shows 'Umbrella-shaped' (Umbrella- 'zone') growth.o Listeria monocytogenes is CAMP-positive due to CAMP factor (like Group-B streptococci). When streaked at right angel to streak of staphylococcus aureus, there is increased zone of hemolysis near staphylococcal streak (arrow head).
Category:
Microbiology
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