A sulfonamide antibiotic that inhibits the growth of Gram-positive and Gram-negative bacteria; inhibits recombinant P. carinii DHPS (IC50 = 0.19 μM); inhibits the growth of clinical isolates of M. tuberculosis (MIC90 = 10 mg/L) and of N. meningitidis (MICs = 5-2,000 mg/L); inhibits the growth of A. pleuropneumoniae, S. choleraesuis, S. typhimurium, P. multocida, S. equi, and S. suis (MIC90s = T. gondii infection when used at a dose of 40 mg/kg per day in combination with pyrimethamine