How do fluoroquinolones exert their antimicrobial effect?

• A. By disrupting cell wall synthesis
• B. By inhibiting bacterial DNA synthesis
• C. By blocking protein synthesis
• D. By altering the cell membrane permeability

Answer: (B)

Fluoroquinolones exert their antimicrobial effect primarily by inhibiting bacterial DNA synthesis. They achieve this through the targeting of specific enzymes known as topoisomerases, particularly DNA gyrase and topoisomerase IV. These enzymes are essential for bacterial DNA replication, repair, and other processes that maintain DNA integrity. When fluoroquinolones bind to these enzymes, they prevent the necessary unwinding and re-ligation of DNA strands. This disruption halts DNA replication, thereby leading to bacterial cell death or inhibition of growth.

Because of their mechanism of action, fluoroquinolones are effective against a broad range of bacteria, making them a valuable option in treating various infections. Their role in interfering with DNA synthesis sets them apart from other classes of antibiotics that may target different aspects of bacterial biology, such as cell wall synthesis, protein synthesis, or membrane integrity.