Ureaplasma parvum and the vaginal microbiota

The vaginal microbiome displays the first line of defense against sexually transmitted pathogens and plays a key role in human reproduction. Among the most prevalent pathogens colonizing the vagina is Ureaplasma parvum, a bacterium with association to various vaginal health issues but under debate about its importance and functional role in disease conditions. We herein sought to determine the relation between the women´s vaginal microbiota and the presence and acquisition of U. parvum. We performed longitudinal sampling of women´s self-sampled cervical swabs, recorded demographic data, data on sexual behavior and previous sexually transmitted infections and performed STI-testing every 6 months. The vaginal microbiota was analyzed using 16S rRNA gene-based analysis in conjunction with predictive modelling of functional pathway abundances within the microbiome. A logistic regression model was built on the basis of microbial volatility to enable prediction of U. parvum acquisition. We report increased number of sexual partners and duration of sexual activity in women positive for U. parvum. Microbial composition largely reflects the white population of study participants. Within our cohort, women with CST IV-B display enhanced prevalence of U. parvum at inclusion to the study, however, U. parvum is present in a fraction of all recorded CST apart from CST II. Presence of U. parvum is generally highlighted by higher a-diversity. Functional difference of the microbiome between U. parvum-positive and U. parvum-negative women is displayed by accompanying bacterial taxa (e.g. Gardnerella spp.) with increased presence of the bifido shunt, which produces acetate. We identified volatility of Lactobacillus crispatus and L. iners as a potent predictor of U. parvum acquisition when considering sexual behavior as a central risk factor. Our data show, that in women with sexual risk behavior and increase of volatility of the two most abundant vaginal Lactobacillus species predicts the risk of U. parvum acquisition while presence of U. parvum is associated to functional changes within the microbiome transferred through associated taxa, which predictively lead to unbalanced acetate vs. lactate availability in the vagina. This disbalance may increase susceptibility to further STIs. Our data are, thus, of particular importance for a better understanding of the variability of the vaginal microbiome and it´s interaction with sexually transmitted pathogens.