This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anti Microbial, Subject name: Pharmacology
Ciprofloxacin acts on 
Select and explain. 
A. DNA histone proteins, B. DNA gyrase, C. Camp, D. mRNA polymerase
B: DNA gyrase
Answer: B: DNA gyrase 
Explanation: Ans. is 'b' i.e., DNA gyrase Major mechanism of action of fluoroquinolone is inhibition of bacterial enzyme DNA gyrase.Recent evidence indicates that in gram positive bacterias, the major target is topoisomerase IV.So greater affinity for topoisomerase IV may confer higher potency against gram positive bacteria.