Survival of Trichomonas vaginalis in wet preparation and on wet mount

Microscopy is an insensitive method for detection of Trichomonas vaginalis, but is widely used because it is both rapid and inexpensive. Diagnosis of trichomoniasis by microscopy requires that motile forms be identified in vaginal fluid samples. However, microscopy cannot always be performed immediately after sample collection. The objective of this study was to assess the impact of sample storage at room temperature on trichomonad motility.

Vaginal swab samples from 77 women positive for T vaginalis infection were collected to determine the impact of storage on wet preparations (swabs in plastic tubes with saline) and wet mounts (samples placed onto a glass slide with a coverslip). Samples were read at 400× every 30 min for the first hour and then once per hour thereafter until there were no motile trichomonads observed.

For wet preparations, motility was 100% at 30 min, 99% at 60 min and decreased by 3%-15% each subsequent hour, with samples having a lower density of trichomonads losing motility more quickly. Trichomonad motility diminished more rapidly in wet mounts compared with wet preparations, with a 20% decrement in motility in 60 min.

These data suggest that vaginal fluid samples for diagnosis of trichomoniasis should be stored in saline rather than on microscope slides until they are examined under the microscope and samples should be evaluated by microscopy within an hour of collection. These findings also suggest that clinical sites which cannot perform microscopy within 1 h of sample collection should consider the use of other diagnostic tests.