Association between Trichomonas vaginalis and vaginal bacterial community composition among reproductive-age women.

Objectives: Some vaginal bacterial communities are thought to prevent infection by sexually transmitted organisms. Prior work demonstrated that the vaginal microbiota of reproductive-age women cluster into 5 types of bacterial communities; 4 dominated by Lactobacillus species (L. iners, L. crispatus, L. gasseri, L. jensenii) and 1 (termed community state type (CST) IV) lacking significant numbers of lactobacilli and characterized by higher proportions of Atopobium, Prevotella, Parvimonas, Sneathia, Gardnerella, Mobiluncus, and other taxa. We sought to evaluate the relationship between vaginal bacterial composition and Trichomonas vaginalis.
Methods: Self-collected vaginal swabs were obtained cross-sectionally from 394 women equally representing 4 ethnic/racial groups. T. vaginalis screening was performed using PCR targeting the 18S rRNA and β-tubulin genes. Vaginal bacterial composition was characterized by pyrosequencing of barcoded 16S rRNA genes. A panel of 11 microsatellite markers was used to genotype T. vaginalis. The association between vaginal microbiota and T. vaginalis was evaluated by exact logistic regression.
Results: T. vaginalis was detected in 2.8% of participants (11/394). Of the 11 T. vaginalis-positive cases, 8 (72%) were categorized as CST-IV, 2 (18%) as communities dominated by L. iners, and 1 (9%) as L. crispatus-dominated (P = 0.05). CST-IV microbiota were associated with an 8-fold increased odds of detecting T. vaginalis compared with women in the L. crispatus-dominated state (OR: 8.26, 95% CI: 1.07-372.65). Seven of the 11 T. vaginalis isolates were assigned to 2 genotypes.
Conclusion: T. vaginalis was associated with vaginal microbiota consisting of low proportions of lactobacilli and high proportions of Mycoplasma, Parvimonas, Sneathia, and other anaerobes.