Cryosurvival of Trichomonas vaginalis during cryopreservation of human semen.

Despite a 90% cryosurvival of Trichomonas vaginalis in their growth medium trypticase yeast maltose (TYM) with DMSO, none of these parasites have previously been observed to survive during cryopreservation of infected human semen with glycerol (Andrologia 18, 323 (1986)). This could have been due to the failure of the culture method used to detect low numbers of survivors. The prospects of possible transmission of T. vaginalis by artificial insemination with cryobanked (-196 degrees C) semen prompted an investigation of the cryosurvival of this parasite in the presence of semen with the cryoprotectant glycerol, using a more sensitive culture method for viability evaluation. Semen and seminal fluid from the same 23 ejaculates, as well as culture medium, were inoculated with small clinical numbers of T. vaginalis and evaluated as to their survival before and after cryopreservation. Results indicated: (i) The highest cryosurvival of T. vaginalis (4.5%) was in cryobanked (glycerolated) semen, (ii) semen, as well as glycerol, shows cryoprotective action, and (iii) glycerol reduced survival of parasites in semen, seminal fluid, and TYM medium during exposure prior to freezing. Clinical information on infectivity of small numbers of T. vaginalis and the data presented here suggests that these organisms could be transmitted by artificial insemination with infected cryobanked human semen.

The effect of ionizing radiation on the viability of Trichomonas vaginalis.

1. The effects of continuous gamma radiation on the viability of Trichomonas vaginalis (ATCC 30001) were assessed by a colony count technique. 2. A triphasic survival curve showed an initial shoulder (Dq) of 3 Gy followed by three linear curves with D0 values of 34, 300, and 90 Gy. 3. Sterilization of 10(6) cells/ml occurred from 1600 to 1800 Gy of radiation. 4. Population growth, subsequent to radiation exposure of 17-100 Gy, showed an increased lag time followed by a faster rate of growth, compared with unirradiated cells. 5. Trichomonas vaginalis is more sensitive to ionizing radiation than free-living protozoa and appears as radiosensitive as those parasitic protozoa examined in radioattenuation experiments.

Difference in effect of dog seminal fluid and human seminal fluid and semen on in vitro survival of Trichomonas vaginalis.

The authors examined the ability of dog seminal fluid to serve as an animal model in order to study survival of Trichomonas vaginalis in human urogenital secretions. Two strains were used: SVI-1, a recent isolate from a male patient, and ATCC 30001, a strain that has been cultured for many years. The authors incubated the T. vaginalis strains in dog seminal fluid, human seminal fluid, and human semen, at 37 degrees C for 6, 12, and 24 hrs. For both strains, survival in dog seminal fluid was much poorer than that in human semen and seminal fluid, zero survival being noted at 24 hrs. The SVI-1 strain survived significantly better than ATCC 30001 in all secretions. Data from experiments using isolates from two female patients, but incubated in human seminal fluid alone, agreed with results obtained with SVI-1. Dog seminal fluid may not be a suitable substitute for human secretions in T. vaginalis studies, and long-term culture may decrease the ability of T. vaginalis to survive in the male urogenital tract.

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.