This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cell Wall Synthesis Inhibitors, Subject name: Pharmacology
Which is not a bacterial drug resistance mechanism? 
Select and explain. 
A. By synthesizing enzymes against antibiotics, B. By altering porin channels, C. By actively effluxing the drug out of the cell, D. By inhibiting DNA gyrase or topoisomerase activity
D: By inhibiting DNA gyrase or topoisomerase activity
Answer: D: By inhibiting DNA gyrase or topoisomerase activity 
Explanation: Resistance to antibiotics occurs by following mechanism. By synthesizing enzymes against antibiotics : Penicillinases , Beta lactamases, Aminoglycoside inactivating enzymes. By altering porin channels, so the drug is not able to enter inside. Resistance to aminoglycosides occurs by this mechanism. By actively effluxing the drug out of the cell : resistance to tetracyclines occurs by this mechanism. Inhibition of DNA gyrase or topoisomerase activity is mechanism of action of flouroquinolones rather than mechanism of acquisition of resistance. So, answer is 'D'.