Characterization of the vaginal microbiota of healthy Canadian women through the menstrual cycle

Abstract

BackgroundThe vaginal microbial community plays a vital role in maintaining women’s health. Understanding the precise bacterial composition is challenging because of the diverse and difficult-to-culture nature of many bacterial constituents, necessitating culture-independent methodology. During a natural menstrual cycle, physiological changes could have an impact on bacterial growth, colonization, and community structure. The objective of this study was to assess the stability of the vaginal microbiome of healthy Canadian women throughout a menstrual cycle by using cpn60-based microbiota analysis. Vaginal swabs from 27 naturally cycling reproductive-age women were collected weekly through a single menstrual cycle. Polymerase chain reaction (PCR) was performed to amplify the universal target region of the cpn60 gene and generate amplicons representative of the microbial community. Amplicons were pyrosequenced, assembled into operational taxonomic units, and analyzed. Samples were also assayed for total 16S rRNA gene content and Gardnerella vaginalis by quantitative PCR and screened for the presence of Mollicutes by using family and genus-specific PCR.ResultsOverall, the vaginal microbiome of most women remained relatively stable throughout the menstrual cycle, with little variation in diversity and only modest fluctuations in species richness. Microbiomes between women were more different than were those collected consecutively from individual women. Clustering of microbial profiles revealed the expected groupings dominated by Lactobacillus crispatus, Lactobacillus iners, and Lactobacillus jensenii. Interestingly, two additional clusters were dominated by either Bifidobacterium breve or a heterogeneous mixture of nonlactobacilli. Direct G. vaginalis quantification correlated strongly with its pyrosequencing-read abundance, and Mollicutes, including Mycoplasma hominis, Ureaplasma parvum, and Ureaplasma urealyticum, were detected in most samples.ConclusionsOur cpn60-based investigation of the vaginal microbiome demonstrated that in healthy women most vaginal microbiomes remained stable through their menstrual cycle. Of interest in these findings was the presence of Bifidobacteriales beyond just Gardnerella species. Bifidobacteriales are frequently underrepresented in 16S rRNA gene-based studies, and their detection by cpn60-based investigation suggests that their significance in the vaginal community may be underappreciated.

Molecular Signatures of Immune Activation and Epithelial Barrier Remodeling Are Enhanced during the Luteal Phase of the Menstrual Cycle: Implications for HIV Susceptibility

“…Our findings are only inclusive of the 19 bacterial proteins confidently identified using our proteomics method; however, our results appear to be consistent with those of a pyrosequencing study examining the microbiota changes over the menstrual cycle of Canadian women. The study found the vaginal microbiome of most women to be relatively stable, and most women were predominantly colonized by Lactobacillus and Bifidobacterium species (58).…”

Temporal and spatial variation of the human microbiota during pregnancy

“…In nonpregnant women, longitudinal studies of the vaginal microbiota have demonstrated stability when viewed at a weekly timescale, punctuated by occasional daily fluctuations (25,(27)(28)(29)(30)(31)(32). These studies also documented significant variability among individuals with respect to the typical vaginal CST and its level of stability.…”

The Human Microbiome during Bacterial Vaginosis

“…Studies of microbiota-host interactions have to control for menstrual cycle phase, which affects both cytokine levels (145,146) and microbial composition (147,148). Cervical ectopy (columnar epithelium replacing the squamous multilayer epithelium of the ectocervix), which is hormone dependent and especially common in adolescents, is also characterized by higher levels of proinflammatory mediators (146) and a shift to BV microbiota (149).…”