The short-term variability of bacterial vaginosis diagnosed by Nugent Gram stain criteria among sexually active women in Rakai, Uganda.

BACKGROUND: Studies evaluating clinical and behavioral factors related to short-term fluctuations in vaginal microbiota are limited. We sought to describe changes in vaginal microbiota evaluated by Gram stain and assess factors associated with progression to and resolution of bacterial vaginosis (BV) at weekly intervals.
METHODS: A cohort of 255 sexually experienced, postmenarcheal women provided self-collected vaginal swabs to assess vaginal microbiota by Nugent score criteria at weekly visits for up to 2 years contributing 16,757 sequential observations. Absolute differences in Nugent scores (0-10) and transition probabilities of vaginal microbiota states classified by Nugent score into normal (0-3), intermediate (4-6), and BV (7-10) between visits were estimated. Allowing each woman to serve as her own control, weekly time-varying factors associated with progression from normal microbiota to BV and resolution of BV to normal microbiota were estimated using conditional logistic regression.
RESULTS: The distribution of absolute difference in Nugent scores was fairly symmetric with a mode of 0 (no change) and a standard deviation of 2.64. Transition probabilities showed weekly persistence, was highest for normal (76.1%) and BV (73.6%) states; whereas, intermediate states had similar probabilities of progression (36.6%), resolution (36.0%), and persistence (27.4%). Weekly fluctuation between normal and BV states was associated with menstrual cycle phase, recency of sex, treatment for vaginal symptoms, pregnancy, and prior Nugent score.
CONCLUSIONS: Weekly changes in vaginal microbiota were common in this population. Clinical and behavioral characteristics were associated with vaginal microbiota transitioning, which may be used to inform future studies and clinical management of BV.