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.

Highlights

  • The vaginal microbial community plays a vital role in maintaining women’s health

  • The vaginal microbiota of reproductive-aged women has traditionally been characterized by culture-based techniques as dominated by Lactobacillus species, which, among other roles, produce lactic acid, biosurfactants, hydrogen peroxide, and other factors that create an inhospitable environment for pathogenic bacteria [2,3,4,5,6,7]

  • Detailed community profiling with culture-independent techniques has demonstrated that “healthy” microbial communities are usually dominated by Lactobacillus crispatus, Lactobacillus iners, Lactobacillus gasseri, Lactobacillus jensenii, or a combination of these species, and in a small portion of women, “mixed” profiles are depleted of lactobacilli and consist of bacteria such as Gardnerella, Prevotella, Atopobium, Megasphaera, and Streptococcus [8,9,10,11,12,13,14]

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Summary

Introduction

The 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. Detailed community profiling with culture-independent techniques has demonstrated that “healthy” microbial communities are usually dominated by Lactobacillus crispatus, Lactobacillus iners, Lactobacillus gasseri, Lactobacillus jensenii, or a combination of these species, and in a small portion of women, “mixed” profiles are depleted of lactobacilli and consist of bacteria such as Gardnerella, Prevotella, Atopobium, Megasphaera, and Streptococcus [8,9,10,11,12,13,14] The latter has challenged our traditional understanding of the “healthy vaginal microbiome,” and raises questions about the structure and function of this community and the host response to it. In at least some cases, the overall functional characteristics of the community are predicted to be maintained, despite the fluctuations in the bacterial composition, because the shifts in relative dominance may be limited to different lactic acidproducing bacterial species [13]

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