Trichomonas vaginalis: comparison of primers for implementation as an in-house PCR in rural Vellore, South India.

Background: Trichomonas vaginalis (TV) accounts for the highest burden of curable, non-viral sexually transmitted infections worldwide. Prevalence in India ranges from 0.4 to 27.4% in women and 0.0-5.6% in men. In 2015, the prevalence of TV among pregnant women of rural Vellore was 3.11% using Sekisui OSOM® Trichomonas test and culture methods. Molecular methods are the most sensitive, rapid diagnostic tool for Sexually Transmitted Infection's (STI) albeit cost hinders implementation of commercial platforms. To determine a sensitive, sustainable molecular method, we compared three targets (Adhesin AP65, cytoskeleton Beta-tubulin BTUB 9/2 and TVK 3/7) with the highest published diagnostic accuracy against microscopy, culture and Real Time PCR (RT- PCR). Materials & methods: Six-hundred adult, sexually active women attending the Obstetrics-Gynaecology rural out-patient clinic the Rural Unit for Health and Social Affairs (RUHSA) from July 2020 - February 2021 were enrolled. A vaginal lateral and posterior fornix specimen was inoculated, onsite, into Biomed InPouch® TV culture and smeared onto a slide for fluorescence microscopy using Acridine orange. A flocked nylon swab specimen for PCR was used to determine the sensitivities of the Adhesin AP65, cytoskeleton Beta-tubulin BTUB 9/2 and TVK 3/7 gene targets. Seegene Allplex™ STI Essential Assay, S.Korea was used to confirm TV positives. Results: Nine specimens (9/600, 1.5%) were positive for TV. There was a 100% correlation between Biomed InPouch TV® culture, PCR with TVK 3/7 and RT-PCR while a correlation of 66.6% with BTUB 9/2 and AP65 gene targets. Clinically, 77.7% (n = 7) presented with white-greenish discharge per vagina, 11% (n = 1) with infertility, 22.2% (n = 2) were asymptomatic. Eight of nine patients (88.9%) had co-infections with other bacterial STIs. Prevalence of TV coinfection with Neisseria gonorrhoea was 1.1%. Conclusion: Current hospital-based prevalence of TV in rural Vellore was 1.5%. Repetitive DNA target TVK 3/7 was more sensitive than AP65 and BTUB 9/2 primers. [ABSTRACT FROM AUTHOR]