This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Microbiology
[{'content': 'All are true about listeria except \nSelect and explain. \nA. Gram positive, B. PALCAM agar is used for isolation, C. Characteristic tumbling motility at 37degC, D. Umbrella shaped growth', 'role': 'user'}, {'content': 'Answer: C \nExplanation: L. monocytogenes is a gram-positive&; coccobacillus&;(coccoid rod) with a tendency to occur in chains. Peritrichous flagella are produced by the bacillus optimally at 20-30degC but only scantily or not at all at 37degC Culture media used for isolation are blood agar, chocolate agar, and PALCAM agar. It grows on ordinary media within a temperature range of 1deg to 45degC. Most cases of human disease are caused by serotypes 1/2a, 1/2b and 4b. The organism can be found as a pa of the gastrointestinal flora in healthy individuals. Human disease due to L. monocytogenes generally occurs in the setting of pregnancy or immunosuppression REF : ananthanarayana 10th ed', 'role': 'assistant'}]