Comparison of different hypervariable regions of 16S rRNA for taxonomic profiling of vaginal microbiota using next-generation sequencing

The exploration of vaginal microbiota by using next-generation sequencing (NGS) of 16S ribosomal RNA (rRNA) gene is widely used. Up to now, different hypervariable regions have been selected to study vaginal microbiota by NGS and there is no standard method for analysis. The study aimed to characterize vaginal microbiota from clinical samples using NGS targeting the 16S rRNA gene and to determine the performance of individual and concatenated hypervariable region sequences to generate the taxonomic profiles of the vaginal microbiota. Fifty-one vaginal DNA samples were subjected to 16S rRNA gene NGS based on the Ion Torrent PGM platform with the use of two primer sets spanning seven hypervariable regions of the 16S rRNA gene. Our analysis revealed that the predominant bacterial genera were Lactobacillus, Gardnerella and Atopobium, which accounted for 78%, 14% and 2%, respectively, of sequences from all vaginal bacterial genera. At the species level, Lactobacillus iners, Gardnerella vaginalis and Atopobium vaginae accounted for 72%, 10% and 6%, respectively, of the bacterial cells present. Analyses using the V3 region generally indicated the highest bacterial diversity followed by the V6-V7 and V4 regions, while the V9 region gave the lowest bacterial resolution. NGS based on the 16S rRNA gene can give comprehensive estimates of the diversity of vaginal bacterial communities. Selection of sequences from appropriate hypervariable regions is necessary to provide reliable information on bacterial community diversity.