Which of the following drugs is available without a prescription in the US and targets cell wall synthesis?

Recall the mechanism of action for each drug: Vancomycin inhibits cell wall synthesis but is prescription-only; Bacitracin inhibits cell wall synthesis and is commonly found in OTC topical antibiotic ointments; Neomycin targets protein synthesis and is also OTC but does not affect the cell wall; Isoniazid inhibits mycolic acid synthesis in mycobacterial cell walls but requires a prescription.