after treatment
The samples were rewarmed before detection, and DNasy PowerWater Kit ( Qiagen, Hilden, Germany ) was used to extract total bacterial genomic DNA from vaginal swab secretion. Qubit dsDNA BR analysis kit ( Invitgen, USA ) and Qubit fluorescence analyzer were used to quantify DNA, and Aliquot was run on 1 % agarose gel for quality inspection.     Using the extracted DNA as template, the 16SrRNA-V4 gene fragment was amplified. The primer sequences were 515F ( 5 ' -GTGCCAGCMGCCGCGGTAA-3 ' ) and 806R ( 5 ' -GGACTACHVGGGGTWTCTAAT-3 ' ). Both forward and reverse primers were labeled with Illumina connector, PAD and connector sequences. The amplified library was identified by Agilent 2100 bioanalyzer. The verified library was sequenced on the Illumina HiSeq 2500 platform ( Wuhan Huada Gene, China ) according to the Illumina standard pipeline, and a 2  261 bp double-end sequencing sequence was generated.