Utility of antimicrobial susceptibility testing in Trichomonas vaginalis-infected women with clinical treatment failure.

Antimicrobial resistance is one of the causes of treatment failure in women after standard nitroimidazole therapy for Trichomonas vaginalis infections. The Centers for Disease Control and Prevention provides drug susceptibility testing and guidance for treatment failures but the efficacy of the alternate recommendations has not been assessed. T. vaginalis isolates from women who had failed at least 2 courses of standard therapy for trichomoniasis were submitted to the Centers for Disease Control and Prevention for susceptibility testing. Alternative treatment recommendations were provided based on in vitro drug susceptibility results and clinical outcomes were collected. Drug susceptibility results were available for 175 women tested between January 2002 and January 2008. In vitro, 115 of the 175 isolates demonstrated metronidazole resistance. For all isolates resistant to metronidazole, in vitro resistance to tinidazole was similar or lower. Clinical treatment outcomes were available for 72 women. Of the women receiving an alternative recommended nitroimidazole regimen, 30 (83%) of 36 were cured compared with 8 (57%) of 14 women who received a lower dose than recommended. Clinical and microbiologic success was attained in 59 (82%) of 72 women whose follow-up information was available, with some women requiring multiple treatment courses. Clinical and microbiologic cure rates were higher for women who were treated in accordance with the recommendation provided after in vitro testing compared with those who received a lower dose or a different drug. Susceptibility testing leading to tailored treatment may have a beneficial role for management of women with persistent trichomoniasis.