Real-time PCRs for detection of Trichomonas vaginalis beta-tubulin and 18S rRNA genes in female genital specimens

Abstract

Trichomonas vaginalis is the cause of one of the most common types of vaginitis, trichomoniasis. The incidence of trichomoniasis in developed countries has decreased substantially during the past decade, but high prevalence of this disease can still be found in rural and remote areas of Australia. Clinical manifestations of symptomatic women are generally non-specific, but include vaginal discharge, vaginitis and irritation. T. vaginalis infection has also been linked to the increased risk of human immunodeficiency virus transmission. Current diagnosis of T. vaginalis relies on the visualization of motile organisms in a wet-mount preparation. Culture is used mainly in reference laboratories. The latter two methods require viable organisms and would not be suitable for use where transportation of specimens can be delayed. Two real-time fluorescence resonance energy transfer (FRET) hybridization probe PCR assays were used in this study to test for T. vaginalis DNA, targeting the beta-tubulin and 18S rRNA genes. We tested 500 randomly selected female patients, in an STD setting, for T. vaginalis DNA. The FRET PCRs targeting the beta-tubulin gene and the 18S rRNA gene detected 96 % (85/89) and 100 % (89/89) , respectively, of the positive specimens (first-void urine sample or genital swabs). Wet-mount microscopy was performed on 76 of these PCR-positive specimens and showed a sensitivity of 38 % (29/76). The prevalence, by PCR, of trichomoniasis was 18 % in this study. The two real-time PCRs developed in this study, targeting different genetic regions of the organism, provide a rapid, sensitive and specific diagnosis of T. vaginalis infection.