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': 'All of the following statement are true about Staphylococci except : \nSelect and explain. \nA. A majority of infection caused by coagulase (-) ve Staph. are due to staph epidermidis, B. β -Lactmase production is under plasmid control, C. Expression of methicillin resistance in Staphylococcus aureus increases when it is incubated at 37 degree C on blood agar, D. Methicillin resistance in Staph. aureus is independent of b-Lactmase production', 'role': 'user'}, {'content': 'Answer: C \nExplanation: “Methicillin resistance is expressed more when Staph. is incubated at 30 0 C than at 37 0 C.”\nPenicillin resistance in Staphylococcus is by following ways :\n1. Production of β lactmase :\n\nPlasmid mediated inducible enzyme which is transmitted by transduction (more commonly) or conjugation.\n\nNow only <5% of strains of staph are sensitive to penicillin.\n\nHospital strains mostly form type A penicillinase.\nSame plasmid carry genes for resistance to tetracycline, Erythromycin, Aminolgycoside too.\n\n2.\xa0 Altered penicillin binding protein :\n\nDue to production of novel penicillin binding protein PBP2a. The protein is synthesized by mecAgene.\nChromosomally mediated expressed more at 30 0 C than at 37 0 C.\nResponsible for resistance against penicillinase resistant penicillin such as methicilin, cloxacillin. Strains are called MRSA (Methicillin resistant Staph. aureus).\n\n3. Tolerance to pencillin :\n\nBacteria only inhibited not killed.', 'role': 'assistant'}]