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
Which is NOT TRUE with regards to antibiotic resistance in bacteria? 
Select and explain. 
A. Most common mechanism is production of antibiotic destroying enzymes, B. Lack of target binding site may be mechanism of resistance in some enterococci against vancomycin, C. Plasmid mediated resistance is transmitted only veically, D. Target binding shifting is the mechanism in some pneumococci
C: Plasmid mediated resistance is transmitted only veically
Answer: C: Plasmid mediated resistance is transmitted only veically 
Explanation: Plasmid mediated resistance can be transmitted both horizontally and veically. Routes of horizontal transfer of plasmid mediated resistance are conjugation, transduction and transformation. 3 main mechanisms of drug resistance: Production of beta lactamases: Most common mechanism of penicillin resistance in both gram +ve and -ve bacteria. Alteration of PBP (penicillin binding proteins ): Seen in gram +ve bacteria. This is the basis for methicillin resistance in MRSA also basis for penicillin resistance in pneumococci and enterococci. Impaired penetration: Seen only in gram -ve bacteria PBP are localised on outer surface of cell membrane and not on cell wall. PBP are essential for synthesis of cell wall.