Mechanism of action — cephalosporins and penicillins in antimicrobial therapy Cephalosporins and penicillins primarily interfere with which critical bacterial process?

Introduction / Context:
Penicillins and cephalosporins are the prototypical beta-lactam antibiotics. Their shared mechanism underpins their clinical utility, resistance patterns, and safety profile. Understanding this mechanism helps interpret laboratory susceptibility results and predict synergy with other drugs.

Given Data / Assumptions:

• Bacterial cell walls require peptidoglycan cross-linking for structural integrity.
• Penicillin-binding proteins (PBPs) catalyze transpeptidation.
• Beta-lactams resemble the D-Ala-D-Ala dipeptide substrate.

Concept / Approach:
Beta-lactams covalently acylate PBPs, blocking transpeptidation and, in some cases, transglycosylation, leading to cell lysis by autolysins. This explains their bactericidal activity in actively dividing bacteria. They do not target ribosomes, DNA, or folate pathways; those are targeted by other classes (for example, macrolides, fluoroquinolones, trimethoprim-sulfonamide).

Step-by-Step Solution:
Identify the drug class: beta-lactams (penicillins, cephalosporins).Recall target: PBPs in the cell wall synthesis pathway.Exclude other mechanisms (protein, DNA, membrane) used by different classes.Choose cell wall synthesis inhibition via PBPs as the correct mechanism.

Verification / Alternative check:
Beta-lactamase production or altered PBPs (for example, PBP2a in MRSA) confers resistance, further confirming PBPs as the key target.

Why Other Options Are Wrong:
Protein synthesis inhibitors include aminoglycosides/macrolides; DNA function is targeted by fluoroquinolones/metronidazole; membrane disruptors include daptomycin/polymyxins; folate pathway is inhibited by trimethoprim-sulfamethoxazole.

Common Pitfalls:
Assuming all bactericidal agents disrupt membranes; beta-lactams are cell wall–active, not membrane-active.

Final Answer:
Peptidoglycan cell wall synthesis (penicillin-binding proteins).