Background Vulvovaginal candidosis (VVC) is commonly diagnosed in STD clinic populations and has been found in longitudinal studies to be associated with increased risk for HIV infection. Many women with recurrent VVC relapse even when on prophylactic therapy and VVC often follows antibiotic treatment. Because the type of vaginal bacterial communities may influence yeast colonisation, we sought to compare the vaginal bacterial communities of Candida albicans-positive and C. albicans-negative women using molecular methods.

Methods Self-collected vaginal swabs were obtained cross-sectionally from 396 U.S. women equally representing four ethnic/racial groups. Exclusion criteria included self-report of vaginal discharge and pregnancy. Detection of C. albicans was performed using PCR targeting the 18S rRNA gene. Vaginal bacterial composition was characterised by pyrosequencing of barcoded 16S rRNA genes. The bacterial communities were clustered into five community state types (CSTs); four dominated by Lactobacillus species (L. iners, L. crispatus, L. gasseri, L. jensenii), and one lacking significant numbers of lactobacilli and characterised by higher proportions of strictly anaerobic organisms (termed CST-IV). The relationship between CSTs and C. albicans detection was evaluated by logistic regression. Random forest analysis was used to identify bacterial phylotypes associated with the presence/absence of C. albicans.

Results 83 women (21%) were C.albicans-positive. Women in the L. crispatus- and L. iners-dominated CSTs were 2-fold more likely to have C. albicans detected compared to women in the relatively low-lactobacillus CST-IV (OR:2.42, 95% CI: 1.21–4.85; OR:1.97, 95% CI: 1.00–3.86, respectively). In random forest analysis, individual genera found highly associated with C. albicans-absence were traditional BV-associated bacteria including Campylobacter, Dialister, Peptoniphilus, Prevotella, and Anaerococcus. Lactobacillus was the primary genera associated with C. albicans-presence.

Conclusion Women with a Lactobacillus-dominated microbiota were more likely to be C. albicans-positive. Longitudinal studies of the vaginal microbiome are needed to determine how vaginal bacterial communities interact with Candida spp.