Comparing Asymptomatic vs Symptomatic Bacterial Vaginosis: Clinical Characteristics, Vaginal Microbiota, and Lactic Acid Profiles

BACKGROUND: Irrespective of symptoms, bacterial vaginosis (BV) has been linked to increased risk of sexually transmitted infections (STI) and HIV, yet clinical guidelines recommend treatment only for symptomatic BV (sBV). We compared demographic, clinical, and vaginal microbiota factors between asymptomatic BV (aBV) and sBV. METHODS: Data from a previously conducted vaginitis cohort study were analyzed. Participants with Amsel-BV were classified as sBV if they reported vaginal symptoms and aBV if asymptomatic. Nugent scores were assigned. Cervicovaginal lavage fluid underwent 16S rRNA gene amplicon sequencing, broad-range qPCR, and lactic acid isomer quantitative assays. Wilcoxon rank-sum, Fisher's exact, and Chi-squared tests compared factors between aBV and sBV. Taxonomic differences were evaluated using elastic net modeling and differential abundance testing. RESULTS: Among 70 participants with sBV and 270 with aBV, clinician-assessed abnormal discharge was more common in sBV (86%) than aBV (71%). In adjusted analyses, recent use of metronidazole or clindamycin, more sex partners, and education beyond high school were associated with increased odds for sBV, and injectable contraception with aBV. No consistent differences were observed between sBV versus aBV for other Amsel's criteria, Nugent scores, or vaginal microbiota composition. D- and L-lactic acid levels were slightly higher in sBV than aBV. CONCLUSIONS: Although some demographic, clinical, and behavioral factors differed between sBV and aBV, no consistent differences were found in vaginal microbiota composition; lactic acid isomer levels were low in both groups. Further research is needed to understand why some experience symptoms, to identify whether other biological factors differentiate aBV from sBV, and to evaluate their respective associations with adverse reproductive outcomes.