Determining the Origins of Repeat Trichomonas vaginalis Infections Using Clinical Versus Genotype-Informed Criteria

Background High rates of repeat infections post-treatment are reported in women infected with Trichomonas vaginalis (TV). Determining the origin of repeat infections is generally limited to clinical queries of adherence to treatment and sexual exposure. The purpose of this study was to add micro-satellite (MS) genotype data to classification criteria for origin of repeat TV infection, and examine if the addition of TV genotype changes classification as treatment failure, re-infection, or new infection Methods Women were enrolled at clinics in Birmingham, AL; Jackson, MS; and New Orleans, LA as part of a randomized clinical trial comparing single-dose (2 g) and multi-dose (500 mg twice daily x 7 days) metronidazole (MTZ) treatment regimens. Participants provided vaginal swabs and completed a behavioral audio-computer assisted self-interview (ACASI). TV specimens were genotyped at 11 microsatellite (MS) loci. Women with repeat TV infections at TOC, were classified as treatment failure, re-infection or new infections using behavioral and genotype data; classifications were compared. Results Data were available for 45 women. Genotype concordance was defined as <4 MS loci different and genotype discordance was defined as ≥ 4 MS loci different. Clinical criteria vs. genotype-informed criteria classifications were treatment failure (66.7% vs 64.4%) re-infection (26.7% vs. 17.8%) and new infections (6.7% vs. 17.8%) respectively; Bowker’s test of symmetry had Χ 2 =16.00 p=0.0011, indicating differences in results. Conclusions The majority of women, using either criteria, were classified as treatment failure. Clinical assessment may overestimate reinfections and underestimate new infections. Patient counseling should be adapted accordingly. Summary To more precisely determine the origin of repeat Trichomonas vaginalis infection, we compared genotype microsatellite size polymorphism data to clinical criteria and found that clinical data overestimated reinfection and underestimated new infections. Patient counselling should consider new partners.