List three classes of antibiotics that inhibit bacterial cell wall synthesis and a representative drug for each.

• A. Beta-lactams (penicillins, e.g., ampicillin); Glycopeptides (vancomycin); Fosfomycin.
• B. Aminoglycosides (gentamicin); Macrolides (azithromycin); Tetracyclines (doxycycline).
• C. Fluoroquinolones (ciprofloxacin); Lipopeptides (daptomycin); Polymyxins (polymyxin B).
• D. Sulfonamides (sulfamethoxazole); Rifamycins (rifampin); Nitrofurantoin.

Answer: (A)

Antibiotics that disrupt bacterial cell wall synthesis do so by targeting steps in peptidoglycan production, a feature unique to bacteria. Beta-lactams bind penicillin-binding proteins that mediate cross-linking of peptidoglycan strands, preventing the wall from forming properly as the bacteria grow. Ampicillin is a representative drug in this class. Glycopeptides, like vancomycin, attach to the D-Ala-D-Ala terminus of the nascent peptidoglycan chain, blocking addition and cross-linking of units, which halts wall assembly—especially effective against Gram-positive organisms. Fosfomycin blocks an early cytoplasmic step by inhibiting the MurA enzyme, stopping the synthesis of the peptidoglycan precursors before they even become part of the wall. Together, these mechanisms prevent proper cell wall construction, leading to bacterial lysis. Other classes in the list target processes such as protein synthesis, DNA replication, membranes, or metabolic pathways, not cell wall formation.