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': 'Commonest cause of nosocomial infection \nSelect and explain. \nA. Pseudomonas, B. Staphylococci, C. Klebsiella, D. Enterobacteriacea', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Controversial MCQ, no where there is clear cut reference for MC agent of HAI\nInitially hospital outbreaks were caused by Gram positive organisms like Streptococcus pyogenes and the methicillin\xa0resistant Staphylococcus aureus (MRSA)\nPresently Gram negative enteric pathogens (Enterobacteriaceae) including Escherichia coli, Klebsiella and Enterobacter\xa0species have emerged as an important cause\nPseudomonas and Acinetobacter species are also common nosocomial pathogens and are extremely resistant to\xa0common antibiotics and antiseptics.', 'role': 'assistant'}]