Background: The association of the normal physiological cycle to the structural pattern of microbiota in reproductive tract of women at reproductive age has not been extensively explored. This study was undertaken to determine whether the vaginal microbes of women at childbearing age is different among groups defined by urogenital tract infections, childbearing history and menstrual cycle, respectively.
Results: This was a multiple case-control study of women at childbearing age who were assigned to case or control groups according to their states of urogenital tract infections. The participants were also grouped by childbearing history and menstrual cycle. Samples of vaginal swabs were collected and stored at -70℃ until assayed. The V3-V4 regions of 16S rRNA genes were amplified using PCR and sequenced on the Illumina MiSeq platform. We tested the hypothesis of whether the relative abundance of microbial species in vaginal microbiota was different between women with different urogenital tract infections, childbearing history and menstrual cycle. We showed that the vaginal microbial richness(Alpha diversity measured by PD_whole tree) was decreased in normal women(without reproductive tract infections) than in those with bacterial vaginosis (BV), and decreased in pregnant women than in other groups of non-pregnancy. Similarly, women from groups of normal and in pregnancy had lower beta diversity on measure of unweighted_unifrac distance in comparison to those of uninfected and non-pregnant. The top 10 genus relative abundance, especially that Lactobacillus was the most dominant genus with the relative abundance of 71.55% among all samples, did not differ significantly between groups of childbearing history and menstrual cycle analyzed by ANOVA and nonparametric kruskal_wallis.
Lactobacillus iners and Lactobacillus helveticus have the most abundance, totally account for 97.92% relative abundance of genus Lactobacillus. It is proposed that a higher L.helveticus/L.iners ratio is more likely to present in normal women than in the infected and in pregnant than in non-pregnant, although this comparison lacks statistical significance.
Conclusions: The relative abundance of dominant bacterial taxa in vaginal microbial communities of women at childbearing age, characterized with 16S rRNA gene sequence and QIIME based analysis, were not different among groups of childbearing history and menstrual cycle. Women from groups of in pregnancy and without reproductive tract infections had lower alpha and beta diversity. The compositional ratio of the main lactobacillus species may shift depending on the normal physiological cycle and reproductive tract infections.