Tetracyclines and
sulfonamides are no longer effective for the treatment of
chancroid in many parts of the world.
Rifampin and
trimethoprim both possess in vitro activity against Haemophilus ducreyi, the causative agent of
chancroid. In a randomized, controlled study, 22 patients with H. ducreyi-positive genital
ulcers received 600 mg of
rifampin once daily for three days, and 32 patients received 600 mg of
rifampin plus 160 mg of
trimethoprim once daily for three days. Both regimens rapidly eradicated H. ducreyi from
ulcers, with subsequent healing of
ulcers and buboes. Two relapses of
ulcers and one therapeutic failure were observed in the
rifampin-
trimethoprim group, whereas no relapses or failures were noted in the
rifampin group. In addition, all of 16 H. ducreyi-negative
ulcers responded rapidly to treatment with either regimen. In an uncontrolled, open study, 22 H. ducreyi-positive
ulcers were treated with a single dose of
rifampin (600 mg) plus
trimethoprim (160 mg).
Ulcers and buboes resolved by day 14 in all but one patient. Thus, these short-course and single-dose regimens are effective against
chancroid.