What is the mechanism of action for the antibiotic ciprofloxacin against Enterobacteriaceae?

• A. It inhibits bacterial RNA polymerase
• B. It inhibits bacterial cell wall synthesis
• C. It inhibits bacterial DNA gyrase and topoisomerase IV
• D. It disrupts protein synthesis

Answer: (C)

Ciprofloxacin is a fluoroquinolone antibiotic that specifically targets bacterial DNA gyrase and topoisomerase IV, which are essential enzymes for bacterial DNA replication, transcription, repair, and overall genetic stability.

The mechanism of action begins with the antibiotic binding to these enzymes, which leads to the inhibition of their activity. DNA gyrase is responsible for introducing negative supercoils into DNA, which is crucial for DNA replication and transcription. Topoisomerase IV plays a vital role in separating the replicated DNA strands during cell division. By inhibiting these enzymes, ciprofloxacin disrupts the normal process of DNA replication and leads to the accumulation of breaks in the DNA, ultimately resulting in bacterial cell death.

This mechanism explains the effectiveness of ciprofloxacin against Enterobacteriaceae, as it effectively targets the fundamental processes required for bacterial survival and multiplication.