Pyrazinamide exerts its bactericidal activity against Mycobacterium tuberculosis only under which specific condition?

• A Acidic pH, as found within macrophage phagolysosomes ✓
• B Neutral pH inside caseous lesions
• C Alkaline pH of the extracellular cavitary environment
• D Anaerobic conditions irrespective of pH

Explanation

Pyrazinamide is a prodrug converted by bacterial pyrazinamidase into active pyrazinoic acid, which is effective only at acidic pH. Acidic environments exist inside macrophage phagolysosomes and within acute inflammatory areas of tuberculous lesions, making pyrazinamide the key sterilizing drug for intracellular bacilli during the intensive phase. At neutral or alkaline pH it is essentially inactive, which distinguishes it from isoniazid and rifampicin that act across pH ranges.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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