16S metagenome of negative control
Extracted DNA from the DNA/RNA Shield medium provided by ZymoResearch Corp., in which the samples were stored. We used a fresh, unopened DNA/RNA Shield Collection Tube (ZymoResearch Corp., Irvine, CA) and treated the medium as described for all swab samples. In order to test the buffers used during DNA extraction (ZymoResearch Corp, Irvine, CA), we performed a DNA extraction with the ZymoBIOMICS DNA Miniprep Kit (ZymoResearch Corp, Irvine, CA) using 750 microl of sterile H2O.For profiling microbiome composition, the microbial DNA was sent to Novogene Company Limited (Cambridge, UK). To amplify the V3-V4 region of the 16S ribosomal RNA gene, polymerase chain reaction (PCR) with the following primers was used: CCTAYGGGRBGCASCAG, GGACTACNNGGGTATCTAAT.