Trichomonas vaginalis is a common sexually transmitted pathogen causing vaginitis, exocervicitis, and ureteritis in women (Fauts and Kraus 1980). Trichomonas vaginalis infections has been suggested to play a role in the pathogenesis of pre-term birth, pre-term rupture of membranes and delivery of low-birth-weight infants (Cotch et al. 1991; Read and Klebanoff 1993). Recently T. vaginalis infections has been implicated as a cofactor in the transmission of HIV (Laga et al. 1993). Trichomonas vaginalis infection are frequently asymptomatic, and early, accurate diagnosis are required for specific treatment. Routine diagnosis of T. vaginalis usually depends on direct microscopic identification of the parasite in wet mount preparations. However, wet mount examinations detects only 60% and the direct immunofluorescense using monoclonal antibodies detect 86% of culture positive cases in women. Although culture is considered the most reliable diagnostic method, with a sensitivity of >90% for detecting T. vaginalis (Spence et al. 1990), it requires complex media and is time-consuming (daily examination from 2 to 7 days). Furthermore, even redundant culture techniques may miss parasites in low number, defective parasites and organisms not surviving the transfer to cultural medium. Molecular approaches to diagnose T. vaginalis have been reported (Riley et al. 1992; Briselden and Hiller 1994; Jeremias et al. 1994; Kenge et al. 1994; Lin and Shaio 1997). PCR detection of T. vaginalis in clinical samples was first reported by Riley et al. (1992), who found that primers amplifying a 102-bp genomic sequence, termed as A6, detected T. vaginalis in all 24 clinical isolates tested. Using the same primer pairs another study conclude that PCR analysis may be useful in women who were negative by wet mount but whose symptomatic vaginitis remained unexplained (Jeremias et al. 1994). Recently, the target of a family of 650-bp repeat of the T. vaginalis genome used in a single tube nested PCR has been evaluated in 378 clinical vaginal discharges (Shaio et al. 1997). For symptomatic patients, the PCR was as sensitive as culture for detection of T. vaginalis in vaginal discharge. The test was consistently negative in patients whose symptoms were due to bacterial vaginosis and vaginal candidiasis, and for asymptomatic women nested PCR was more sensitive than culture for detection of T. vaginalis. To date, PCR is not a routine detection method in diagnosing T. vaginalis.
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