Beta-lactam antibiotics are bactericidal because they inhibit penicillin-binding proteins (PBPs). The downstream bactericidal event that directly causes cell lysis is:
- A Direct inhibition of transpeptidase causes immediate cell death without autolysis
- B Inhibition of transglycosylase blocks initiation of peptidoglycan synthesis
- C Inhibition of cell wall crosslinking leads to autolysis via activation of autolytic enzymes (murein hydrolases) ✓
- D Peptidoglycan fragments produced bind TLR-2 and cause apoptosis
Correct answer: C. Inhibition of cell wall crosslinking leads to autolysis via activation of autolytic enzymes (murein hydrolases)
Explanation
Beta-lactams inhibit PBP transpeptidases, preventing cross-linking of peptidoglycan; the resulting structural weakness activates bacterial autolytic enzymes (murein hydrolases), which degrade existing peptidoglycan and cause osmotic lysis. Organisms that lack autolytic activity (tolerant strains) are inhibited but not killed despite PBP inhibition. This autolysis-dependent killing explains the phenomenon of beta-lactam 'tolerance'.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.