This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: miscellaneous, Subject name: Microbiology
The most common pathogens responsible for nosocomial pneumonia in the ICU are 
Select and explain. 
A. Gram positive organisms, B. Gram negative organisms, C. Mycoplasma, D. Viral infection
B: Gram negative organisms
Answer: B: Gram negative organisms 
Explanation: Mainly responsible organisms are acinetobacters which are Gram-negative aerobic bacteria. Ref: Ananthanarayan& Paniker&;s textbook of microbiology, 9th edition. Pg no.397