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': 'The most common pathogens responsible for nosocomial pneumonias in the ICU are - \nSelect and explain. \nA. Gram positive organisms, B. Gram negative organisms, C. Gram negative organisms, D. Virus infections', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. is \'b\' i.e., Gram negative organisms "Hospital-acquired (nosocomial) pneumonia is frequently caused by enteric gram-negative bacilli such as E.coli, pseudomonas aeruginosa".', 'role': 'assistant'}]