16S rRNA-Seq of Negative sample: copan transport medium 1
DNA was extracted from endometrial tissue using the Qiagen QIAamp UCP kit with Pathogen Lysis Tube S. The V4 hypervariable region of the 16S rRNA gene was amplified using primers 515F (5-GTGYCAGCMGCCGCGGTAA-3) and 806R (5-ACTACNVGGGTWTCTAAT-3). Amplicons were purified with AMPure XP beads and library quality was confirmed using a High Sensitivity Bioanalyzer. Paired-end sequencing (2  300 bp) was performed on an Illumina MiSeq platform.