Which is not a bacterial drug resistance mechanism?

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'.