Susceptibility of Trichomonas vaginalis to metronidazole: A survey of 76 random isolates

Isolates were cultured in an TYM-medium (MEINGASSNER and HEYWORTH 1982) containing antibiotics for inhibition of bacterial and fungal growth. Inhibitors were omitted from the growth medium when the cultures proved to be free from contaminants. Drug testing on the isolates was usually performed within 10 passages after isolation. The laboratory procedure for susceptibility testing to metronidazole in microtitration plates has been previously reported in detail (MEINGASSNER and THURNER 1979), but differed in the use of TYM-medium instead of CPLM-medium. For the assay, stock cultures of the isolates were prepared by two successive transfers of 5 x 10 to 10 ml medium at 24 hr intervals. The cell density was finally adjusted to 5 x 10 cells per ml by addition of fresh medium. 150 \i\ of this suspension were pipetted into 50 fxl drug solution per well in the plates. The minimal lethal concentration (MLC), taken as the highest dilution in which no flagellar motility could be observed after exposure to the drug for 48 hr, was evaluated under aerobic and anaerobic test conditions. Individual isolates were tested in a mouse assay (MEINGASSNER and THURNER 1979). Mice were infected ectopically by two subcutaneous injections of 0.1 ml inoculum and an intraperitoneal dose of 0.3 ml. The inoculum (4 x 10 cells ml") prepared from a 24 hr culture in TYM-medium plus 0.5% agar. The seed culture was also 24 hr old. Survival in the subcutis and in the peritoneal fluid was tested after oral treatment with 3 doses of 25, 50 or 100 mg kg" each. 8-12 mice were used per dose group.