Topic overview

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These drug groups act at distinct points in bacterial metabolism and nucleic acid replication. Sulfonamides, structural analogs of para-aminobenzoic acid, competitively inhibit dihydropteroate synthase and thereby block folic acid production. Trimethoprim also inhibits folic acid synthesis; together, trimethoprim and sulfamethoxazole (TMP-SMX) have a synergistic effect. Quinolones inhibit DNA gyrase and topoisomerase IV. The topic connects these mechanisms with uses that include urinary, respiratory, and gastrointestinal infections, and examines how resistance can arise through enzyme mutations, efflux pumps, and plasmid-mediated mechanisms. It also highlights adverse effects associated with each group, including Stevens-Johnson syndrome with sulfonamides, bone marrow suppression with trimethoprim, and tendon rupture with quinolones.