Mechanisms of Action of Antibiotics

Basic Mechanisms of action

Disruption of cell wall

Beta-lactams	Bind PBPs and enzymes responsible for peptidoglycan synthesis
beta-lactamase inhibitor	prevents enzymatic degradation of beta-lactams
vancomycin	prevents cross-linking of peptidoglycan layers
isoniazid ethionamide	inhibits mycolic acid synthesis
ethambutol	inhibits arabinoglycan synthesis
cycloserine	inhibits cross linkage of peptidoglycan layers
polymyxin	inhibits bacterial membranes
bacitracin	inhibits bacterial cytoplasmic membrane and movement of peptidoglycan precursors

Inhibition of protein synthesis

aminoglycoside	produces premature release of aberrant proteins from 30S ribosome
tetracycline	prevents polypeptide elongation at 30S ribosome
linezolid	prevents initiation of protein synthesis at 30S ribosome
macrolide clindamycin streptogramins	prevents polypeptide elongation at 50S ribosome

Inhibition of nucleic acid synthesis

quinolone	binds alpha subunit of DNA gyrase
rifampin rifabutin	prevents transcription by binding DNA-dependent RNA polymerase
metronidazole	disrupts bacterial DNA (i.e. cytotoxic)

Antimetabolites

sulfonamides	inhibit dihydropterate synthase and disrupts folic acid synthesis
dapsone	inhibits dihydropterate synthase
trimethoprim	inhibits dihydrofolate reductase and disrupts folic acid synthesis

Binding to mycobacterial wall