design: Bacterial genomic DNA was extracted from swabs using the Qiagen DNA Mini kit (Qiagen, USA) as per the manufacturer's protocol. The extracted DNA yield and purity were evaluated using a NanoDrop 2000 spectrophotometer (Thermo Scientific, Waltham, MA, USA). The V4 hypervariable region of the 16S rRNA gene was then PCR-amplified with appropriate reagent controls to avoid contamination introduced into the experiment. Amplified DNA fragments were sequenced using the Illumina NovaSeq 6000 platform. Sequencing reads were processed using QIIME pipeline V.2.334