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: Pharmacology
The most important mechanism by which gram negative bacilli acquire chloramphenicol resistance is: 
Select and explain. 
A. Decreased permeability into the bacterial cell., B. Acquisition of a plasmid encoded for chloramphenicol  acetyl transferase., C. Lowered affinity of the bacterial ribosome for chloramphenicol., D. Switching over from ribosomal to mitochondrial protein synthesis.
B: Acquisition of a plasmid encoded for chloramphenicol  acetyl transferase.
Answer: B: Acquisition of a plasmid encoded for chloramphenicol  acetyl transferase. 
Explanation: None