Staining of Trichomonas vaginalis with Fluorescent Brighteners

Infection with Trichomonas vaginalis (T. vaginalis) is an important and common sexually transmitted infection that often is unsuspected and undiagnosed. While sensitive laboratory tests such as culture and those based on genetic probes or antigen detection are available, many laboratories still use a relatively insensitive microscopic examination of an unstained wet preparation to diagnosis this infection. Cultured T. vaginalis expresses chitin on its cell surface that fluoresces when stained with calcofluor white (CFW). This study investigated whether CFW improves the sensitivity of microscopic detection of trichomonads. Uvitex 2B and 7 different commercial preparations of CFW were tested with 23 urine and 20 vaginal specimens positive by microscopy for trichomonads. In addition to adding the fluorescence brighteners (FBs) to wet preparations, air-dried smears were stained with the FBs using a variety of fixation methods, FB concentrations, and staining duration. Ten recently isolated strains of T. vaginalis in cultures were also examined. In 40 clinical specimens, no fluorescence was seen with any of the FB staining procedures used, either in wet preparations or smears; 3 vaginal specimens produced only minimal fluorescence. Some of the cultured trichomonads produced fluorescence, depending upon the age of the culture and fixation method. For laboratories using microscopy to detect T. vaginalis in vaginal smears and urine specimens, FBs do not appear to improve sensitivity compared with unstained wet preparations.