Trichomonas vaginalis Susceptibility Testing

Susceptibility Testing

The CDC Division of Parasitic Diseases and Malaria performs susceptibility testing of Trichomonas vaginalis isolates collected from individuals with infections that are refractory to treatment. Susceptibility testing is conducted by broth microdilution for both metronidazole and tinidazole.  Susceptibility data are reported as the minimum lethal dose (MLC) which is defined as the lowest antimicrobial concentration that results in loss of parasite motility in culture.

Currently there are no established breakpoints for metronidazole and tinidazole in T. vaginalis.  CDC is making MLC distribution data available online to aid in the interpretation of Trichomonas susceptibility testing results. These downloadable data contain tables and graphic representations that display MLC distributions for isolates collected from successfully treated individuals and from individuals with infections that are refractory to treatment. CDC will continue to expand this database to include additional data as additional studies are conducted.

Trichomonas vaginalis Clinical Management and Consultation

The CDC Division of STD Prevention provides recommendations on the treatment of various sexually transmitted diseases including Trichomoniasis – STI Treatment Guidelines ( For clinical guidance with the management of recurrent or persistent trichomoniasis, please contact the CDC Division of STD Prevention Trichomonas Clinical Consultation team at Susceptibility testing may be helpful in selection of alternative treatment regimens (1,2).



  1. Bosserman EA, Helms DJ, Mosure DJ, Secor WE, Workowski KA. Utility of antimicrobial susceptibility testing in Trichomonas vaginalis-infected women with clinical treatment failure. Sex Transm Dis. 2011;38(10):983-987.
  2. Workowski, KA, Bachmann, LH, Chan, PA, Johnston, CM, et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep 2021;70(No. RR4): 1-187.