Differential response of chlamydial and ureaplasma-associated urethritis to sulphafurazole (sulfisoxazole) and aminocyclitols.

91 men with non-gonococcal urethritis (N.G.U.) were randomly treated with either sulphafurazole (sulfisoxazole), 500 mg orally q.i.d. for 10 days, or an aminocyclitol (streptomycin or spectinomycin), 2 g intramuscularity for 1 to 3 doses at 12 h intervals. Initial urethral cultures were positive for Chlamydia trachomatis (C) in 36 (40%). Ureaplasma urealyticum (U) was isolated from the urethra or urine from20 (95%) of 21 White men in a first episode of N.G.U. who had negative chlamydia cultures. Sulphafurazole, active against C. trachomatis but not U. urealyticum in vitro, produced a clinical response in 7 of 7 men with C+U- N.G.U. and 5 of 19 with C-U+ N.G.U. (P less than 0-01). Aminocyclitols, active against U. urealyticum but relatively inactive against C. trachomatis in vitro produced a clinical response in 0 of 6 men with C+U-N.G.U., 9 of 11 men with C-U+N.G.U. from whom ureaplasma was eradicated (P less than 0-01), and 0 of 8 with C-U+ N.G.U. from whom ureaplasma was not eradicated. C+U+ N.G.U. responded poorly to both antimicrobials alone. These results support the aetiological importance of both C. trachomatis and U. urealyticum in N.G.U.