Sulfamethizole is a sulfathiazole antibacterial agent. Target: Antibacterial Sulfamethizole is a sulfathiazole antibacterial agent. Sulfamethizole is a competitive inhibitor of bacterial para-aminobenzoic acid (PABA), a substrate of the enzyme dihydropteroate synthetase. The inhibited reaction is necessary in these organisms for the synthesis of folic acid. Sulfamethizole, an inhibitor of dihydropteroate synthetase and the formation of folic acid, inhibited bioluminescence more than growth [1]. Treatment with sulfamethizole resulted in a significant reduction in bacterial counts in all samples from a susceptible strain (MIC, 128 micro g/ml) and a resistant strain (MIC, 512 micro g/ml). Infection with a sulII gene-positive strain (MIC, >2,048 micro g/ml) could not be treated with sulfamethizole, as no effect could be demonstrated in the urine, bladder, or kidneys [2].