**Question:** Fluroquinolone mechanism of action in gram positive organism is by -

A. Inhibition of DNA gyrase
B. Inhibition of topoisomerase IV
C. Inhibition of protein synthesis
D. Inhibition of bacterial cell wall synthesis

**Core Concept:**
Fluroquinolones are a class of broad-spectrum antibiotics that primarily target bacterial DNA replication and transcription. They exert their antibacterial activity by inhibiting two enzymes: DNA gyrase and topoisomerase IV, which are essential for maintaining DNA supercoiling and decatenating DNA, respectively.

**Why the Correct Answer is Right:**
Fluroquinolones exert their antibacterial action in gram-positive organisms primarily through inhibition of DNA gyrase and topoisomerase IV. In gram-positive bacteria, these enzymes play a crucial role in maintaining DNA supercoiling and decatenating DNA, respectively. By inhibiting these enzymes, fluroquinolones disrupt the bacterial DNA replication and transcription processes, ultimately leading to cell death.

**Why Each Wrong Option is Incorrect:**

A. Inhibition of DNA gyrase (Option A) is incorrect because it is the target of action for fluroquinolones in gram-negative bacteria, not gram-positive organisms.

B. Inhibition of topoisomerase IV (Option B) is incorrect because it is the target of action for fluroquinolones in gram-negative bacteria, not gram-positive organisms.

C. Inhibition of protein synthesis (Option C) is incorrect because it is a mechanism of action for other antibiotics, not fluroquinolones specifically.

D. Inhibition of bacterial cell wall synthesis (Option D) is incorrect because it is the target of action for beta-lactam antibiotics, not fluroquinolones.

**Clinical Pearl:**
Fluroquinolones are essential drugs for the treatment of infections caused by gram-negative bacteria due to their specific target of action in these organisms. In contrast, gram-positive bacteria have different defense mechanisms and are generally less susceptible to fluroquinolones, making them a better choice for treating infections caused by gram-negative bacteria.