[In vitro studies on the identification of metronidazole resistant strains of Trichomonas vaginalis (author's transl)].

In order to ascertain the minimal lethal concentration (MLC) of metronidazole for strains of T. vaginalis with varying susceptibility, comparative studies were carried out under different assay conditions. These studies were made under aerobic or anaerobic conditions in microtiter plates and culture tubes respectively, using the following media: CACH with/without agar, CPLM, trichomonas medium (Merck), fluid thioglycollate (BBL), TYM with/without agar and STS modified. Thus only MLC values greater than or equal to 25 microgram/ml proved to be indicate for metronidazole resistant strains of T. vaginalis in the aerobic plate test. Under identical test conditions the MLC of 12.5 microgram/ml can be considered as an intermediate since this value in some cases has been ascertained for both normal sensitive strains and strains with known decreased susceptibility. Due to the irrelevant findings obtained with the CACH medium without agar and the modified STS medium, as well as with anaerobic test methods, these media seem to be unsuitable for the identification of metronidazole resistant strains of T. vaginalis.