[Metronidazole resistance test in vitro in strains of Trichomonas vaginalis isolated from clinical material. 1. Test conditions].

Metronidazole-resistant clinical isolates of Trichomonas vaginalis display an aerobic type of resistance detectable in vitro only if some oxygen is present. Consequently, adjustment of the optimal concentration of O2 in assay system is of critical importance for dependable determination of minimal lethal concentration (MLC) of the drug. The authors demonstrated that decrease of oxygen content in assay media (from 191.2 nM to 49.5 nM O2.ml-1) resulted in increased susceptibility of the drug-resistant strain IR-78 to metronidazole (from MLC 100 micrograms.ml-1 to MLC 25 micrograms.ml-1). Different MLCs were obtained in media of different reducing capacity. Oxygen dependent variations in MLC were also observed in assay systems containing different volumes of medium. The authors discuss effect of these and other variables in methodology of susceptibility assays in order to define conditions of standard procedure.