Which antibiotic does NOT target cell wall synthesis?

• A. Cephalexin
• B. Augmentin
• C. Bacitracin
• D. Moxifloxacin

Answer: (D)

Targeting cell wall synthesis means interfering with peptidoglycan formation, which is essential for bacterial shape and integrity. The drugs that do this block steps like cross-linking of the peptidoglycan or the transport of building blocks across the cell membrane.

The antibiotic that does not target the cell wall is a fluoroquinolone. It acts on DNA replication by inhibiting DNA gyrase and topoisomerase IV, enzymes that manage DNA supercoiling and separation during replication. By stopping replication, it halts bacterial growth without directly weakening the cell wall.

The other options are all cell wall synthesis inhibitors. Cephalexin is a cephalosporin that binds penicillin-binding proteins and prevents cross-linking of peptidoglycan. Augmentin (amoxicillin with clavulanate) is a beta-lactam that also targets PBPs and blocks wall synthesis, with the clavulanate protecting the antibiotic from beta-lactamase degradation. Bacitracin disrupts cell wall construction by interfering with the dephosphorylation of bactoprenol, the carrier that shuttles peptidoglycan precursors across the cell membrane.