Survival of Trichomonas vaginalis in human semen.

Although exposure of Trichomonas vaginalis to human semen is of short duration, any effect that this fluid may have on the urogenital protozoon could affect its transmission, especially if only few trichomonads are present. Small numbers of parasites (about 2500/ml semen) incubated in semen from different donors at 37 degrees C, were found to survive or grow for up to 12 hours in all samples and for up to 24 hours in most. Survival and growth of T vaginalis in semen most resembled that found in Diamond's trypticase, yeast extract, and maltose (TYM) medium without serum supplement, rather than in complete TYM medium and phosphate buffered saline. Contrary to previous reports, semen did not inhibit the survival of T vaginalis, and the presence of trichomonads did not alter motility or numbers of spermatozoa up to 24 hours. The data suggest that semen provides a favourable milieu for transmitting trichomonads.