Trichomoniasis, caused by Trichomonas vaginalis, is the leading nonviral sexually transmitted infection worldwide. We report the selection of a DNA aptamer against a T. vaginalis adhesion protein, AP65, using a microtiter plate-based in vitro combinatorial chemistry process termed systematic evolution of ligands by exponential enrichment. The enriched library pool was sequenced by next-generation sequencing, and several aptamer candidates with high affinity and specificity were identified. The aptamer with the highest affinity and specificity had a K in the low nanomolar range, as confirmed by three different techniques: surface plasmon resonance, enzyme-linked aptamer assay, and biolayer interferometry. The selected aptamer was demonstrated to have a high specificity to the AP65 protein and to T. vaginalis cells with no cross-reactivity to other enteric and urogenital microorganisms. Current work is focused on the development of inexpensive and easy-to-use aptamer-based diagnostic assays for the reliable and rapid detection of T. vaginalis in vaginal swabs.

This is the first study in the Philippines and one of the two reports worldwide to detect the four TVVs and their concurrent infection in a single T. vaginalis isolate.

Background. Metronidazole susceptibility and the presence of Trichomonas vaginalis virus (TVV) are the phenotypes found to be significantly correlated with the microsatellite-based genotypes of T. vaginalis. These phenotypes were assessed in T. vaginalis isolates from select urban areas to determine preliminary “type” of Philippine T. vaginalis. Methods. Culture and microscopy were used to detect T. vaginalis in vaginal swab samples collected from women attending social hygiene clinics in Metro Manila and Angeles City, Philippines. Screening of TVV on T. vaginalis was performed using RNA gel electrophoresis and RT-PCR. A modified protocol for metronidazole susceptibility assay was used to determine the aerobic minimum lethal concentration (MLC) of metronidazole in axenized T. vaginalis isolates. Results. A total of 42 T. vaginalis were screened for the presence of TVV and assayed for metronidazole susceptibility. TVV was detected in 13 of the isolates. All but one of the samples was susceptible to metronidazole. Conclusion. This is the first study to assess the in vitro metronidazole susceptibility of Philippine T. vaginalis isolates. The isolates are generally susceptible to metronidazole even with the presence of TVV. The metronidazole susceptibility and presence of TVV are not enough to classify the isolates into type 1 or type 2.