Introduction Trichomonas vaginalis (TV) is the most prevalent sexually transmitted parasite worldwide. Trichomoniasis is associated with an increased risk of acquiring other sexually transmitted infections and in pregnant women is associated with premature rupture of membranes and preterm delivery. It is important to have high sensitivity diagnostic methods in order to establish appropriate treatments and avoid complications, since approximately 10%–50% of infected women remain asymptomatic. The aim of this study was to evaluate three DNA extraction methods to optimise the detection of TV by PCR.
Methods Vaginal swabs were studied by culture in liquid medium (modified thyoglicolate medium). An aliquot of the original samples was saved for DNA purification by a) using a silica-membrane-based DNA purification commercial kit, b) 10 min boiling and c) 10 min boiling followed by sample dilution. All extracts were analysed by PCR for TV (18S rRNA gene). PCR inhibitors were evidenced by human tnf gene amplification. Samples that resulted TV positive by culture and/or PCR were considered as true positive (expanded gold standard).
Results Fortythree vaginal swabs were included in this study. PCR inhibitors were detected in 1 sample prepared by method a), in 2 samples prepared by method b) and c) hence not further analyse. By culture five samples were positive (12.2%). TV was detected by PCR in a) 12 samples (29.3%) b) 7 samples (17.1%) and c) 8 samples (19.5%). All positive culture samples were detected by method a) and c) and only 4 of them by method b). Considering the expanded gold standard, sensitivity for the TV detection by culture was 41.7%, by method b) 58.3%, c) 66.7% being a) the most sensitive (100%).
Conclusion Currently the TV molecular diagnosis is not routinely performed and there are no standardised molecular detection methods. Considering the high percentage of asymptomatic patients, the use of high sensitivity techniques such as method a) will allow the improvement of diagnostic protocols and the design of prevention and control strategies.