Failure of treatment for chancroid in Rwanda is not related to human immunodeficiency virus infection: in vitro resistance of Haemophilus ducreyi to trimethoprim-sulfamethoxazole.

A comparative open study was performed to evaluate the efficacy of single doses of ciprofloxacin (500 mg) and trimethoprim-sulfamethoxazole (TMP-SMZ; 640 mg/3,200 mg) for the treatment of culture-proven chancroid. Clinical cure or improvement was observed 7 days after treatment in 32 (76.2%) of the 42 patients who received ciprofloxacin and 21 (52.5%) of the 40 patients who received TMP-SMZ (P = .04). Cultures for one (4.5%) of 22 patients not cured with ciprofloxacin and 16 (59.3%) of 27 patients not cured with TMP-SMZ were still positive for Haemophilus ducreyi 7 days after treatment (P < .001). Although 77 (71.3%) of the 108 patients tested were seropositive for HIV-1 antibody, HIV infection and the degree of CD4+ lymphocyte depletion had no effect on clinical and bacteriologic outcome. All isolates of H. ducreyi were highly susceptible to ciprofloxacin (MIC, 0.004-0.06 mg/L). In contrast, resistance to TMP-SMZ (MIC, > or = 4/76 micrograms/mL) was observed in 48.9% of isolates (22 of 45) and was significantly associated with treatment failure. Therefore, the administration of TMP-SMZ, in single or multiple doses, is no longer indicated for the treatment of chancroid in Rwanda.