This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'Which of the following is gram-positive bacillus- \nSelect and explain. \nA. Staphylococcus, B. Streptococcus, C. Listeria, D. Meningococci', 'role': 'user'}, {'content': "Answer: C \nExplanation: Listeria is gram-positive bacillus.\nStaphylococcus and streptococcus are also gram-positive, but they are cocci (not bacilli).\nMeningococci are gram-negative cocci.\n\nAlso know\n\nClinically important spore-forming bacteria are gram-positive → Clostridium, Bacillus.\nListeria is the only gram-positive bacteria that has endotoxin. (Endotoxin is present only in gram-negative organisms).\nOf the gram-negative organisms, only two groups are cocci - Neisseria (meningococcus & gonococcus), veillonella.\nAll other gram-negative organisms are bacilli (including coccobacilli).\nAmongst medically important bacilli '6' are gram (+)ve → Actinomycetes, clostridium, mycobacteria, Bacillus, Listeria, Corynebacterium.\nAll other medically important bacilli are gram-negative.", 'role': 'assistant'}]