A clinical isolate of Pseudomonas aeruginosa shows resistance to ciprofloxacin. Genetic analysis reveals upregulation of the MexAB-OprM efflux pump system. What is the primary mechanism by which this confers resistance?
- A Modification of the DNA gyrase target
- B Enzymatic degradation of the drug
- C Active extrusion of the drug from the bacterial cell ✓
- D Production of a protective Qnr protein
Correct answer: C. Active extrusion of the drug from the bacterial cell
Explanation
The MexAB-OprM efflux pump actively extrudes ciprofloxacin out of the bacterial cell, reducing intracellular drug concentration. Efflux is a common mechanism of multidrug resistance in Pseudomonas aeruginosa, often leading to cross-resistance among multiple antibiotic classes. Modification of DNA gyrase is a chromosomal mutation mechanism. Qnr proteins protect the target. Enzymatic degradation is not a mechanism of fluoroquinolone resistance.
Reference: Lippincott Illustrated Reviews: Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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