“…They reversibly inhibit the synthesis of folic acid through binding to dihydropteroate synthase (DHPS), a catalytic enzyme in the folic acid biosynthesis pathway. Sulfonamide resistance was first reported around 1938, where particular strains of Streptococcus did not respond to the bactericidal effects of sulfonamide (Buttle, 1939). Vertically acquired resistance to sulfonamides is conferred by mutations in the chromosomal DHPS gene (folP), enabling bacteria to produce altered forms of the DHPS enzyme that are resistant to inhibition by the drug (Skold, 2000).…”