We sought to assess time-independent and time-varying factors associated with incidence and spontaneous clearance of molecular-bacterial vaginosis (BV; without treatment).
Midvaginal samples were self-collected daily by 100 participants recruited at the University of Alabama Birmingham for 10 weeks (4778 samples). Vaginal microbiota was characterized by 16S rRNA gene amplicon sequencing and clustered into community state types (CSTs). A low-Lactobacillus CST defined the molecular-BV outcome in this study. Factors associated with molecular-BV incidence and spontaneous clearance were modeled using Andersen-Gill recurrent event Cox models. Community class identified the predominant CST of a participant during follow-up.
Menstruations (adjusted odds ratio [aHR], 2.09 [95% confidence interval, 1.51-2.89] in the prior 24 hours) and CST III (Lactobacillus iners dominated) at the previous sample (aHR, 2.25 [1.48-3.40]) were associated with increased molecular-BV incidence. Participants with a majority of L. iners-dominated samples longitudinally (community class LI) displayed less stable patterns of vaginal microbiota. In LI participants, reduced molecular-BV spontaneous clearance was observed in African American participants (aHR, 0.44 [0.26-0.75]) compared with White participants, older participants (age, 40-49 years [aHR, 0.38; 0.23-0.61]; age, 30-39 years [aHR, 0.48; 0.28-0.83]) compared with participants aged 18 to 29 years, and after douching (0.45 [0.28-0.73] within prior 72 hours).
Although it is now well documented that vaginal microbiota are dynamic, there are few available data on factors associated with spontaneous clearance of molecular-BV. Lactobacillus iners-dominated vaginal microbiota are more likely to be dynamic and associated with different risk factors for incidence and clearance of BV. Among L. iners-dominated participants, age, race, and douching were linked to reduced clearance. Most transitions to molecular-BV during menstruations were short-lived.