AN IN-VITRO METRONIDAZOLE SUSCEPTIBILITY TEST FOR TRICHOMONIASIS USING THE INPOUCH TV(TM) TEST

Objective: An efficient anaerobic culture system, the InPouch TV(TM) t est, was used to determine the susceptibility of Trichomonas vaginalis to metronidazole. Glacial acetic acid was employed as a solvent for m etronidazole. Methods: T vaginalis isolates were cultured from 16 symp tomatic female patients. The 11 who responded to oral metronidazole, 2 50 mg tid for 7 days, were considered as having sensitive trichomonads ; the 5 who remained infected after treatment were considered to have resistant organisms. All isolates were cultured for minimum lethal con centrations (MLC). Metronidazole was added to a series of pouches; two -fold dilution of the most concentrated was 50 mu g/ml and the least w as 0.4 mu g/ml. The inoculum of viable trichomonads was 1 x 105/ml in each pouch. Pouches were incubated at 37 degrees C for 48 h, examined microscopically for motile trichomonads, and then 0.5 ml was subcultur ed to drug free pouches. After 5 days incubation at 37 degrees C, each subculture and culture were examined microscopically for viable trich omonads. Results: Eleven isolates of T vaginalis from patients respond ing to metronidazole treatment had MLC between 0.4 to 3.1 mu g/ml. The MLC from the 5 treatment failure patients were between 12.5 to 50 mu g/ml. Conclusions: For the 16 patients in this study, the MLC values d etermined with the InPouch TV(TM) test differentiated between infectio n caused by metronidazole sensitive and resistant trichomonads. The me an MLC of clinically resistant isolates was approximately eleven fold higher than the mean MLC of clinically sensitive isolates (15 mu g/ml 1.32 mu g/ml). There was a significant difference between clinically r esistant and sensitive isolates (t = 5.47, p < 0.0005). This study sug gests that the InPouch TV(TM) test could be used for distinguishing be tween metronidazole resistant and sensitive isolates.