This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
[{'content': 'A patient appeared in the emergency room with a submandibular mass. A smear was made of the drainage and a bewildering variety of bacteria were seen, including branched, Gram-positive rods. The most clinically appropriate action is \nSelect and explain. \nA. Do no further clinical workup, B. Suggest to the laboratory that low colony counts may reflect infection, C. Determine if fluorescent microscopy is available for the diagnosis of actinomycosis, D. Consider vancomycin as an alternative drug', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The patient has actinomycosis. These laboratory data are not uncommon. There is no reason to work up all the contaminating bacteria. A fluorescent microscopy test for A. israelii is available. If positive, the FA provides a rapid diagnosis. In any event, it may be impossible to recover A. israelii from such a specimen. High-dose penicillin has been used to treat actinomycosis.', 'role': 'assistant'}]