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
Fluoroquinolones act on - 
Select and explain. 
A. DNA histone proteins, B. DNA gyrase, C. Camp, D. mRNA polymerise
B: DNA gyrase
Answer: B: DNA gyrase 
Explanation: Ans. is 'b' i.e., DNA gyrase o Fluoroquinolones (including ciprofloxacin) inhibit DNA gyrase and topoisomerase IV. For gram negative bacteria, the primary target is DNA gyrase, while topoisomerase IV is inhibited in gram positive bacteria.