Multilocus sequence typing and phylogenetic analysis
For the S. aureus , S. epidermidis , P. aeruginosa , and BCC isolates, we conducted multilocus sequence typing (MLST) by amplifying seven housekeeping genes using previously described primer sets (16-19). When aroE of S. aureus was not detected, alternative primers were used: aroE745-up, 5’-TTATCACCGTCGATGCATAGTGCA-3’; aroE255-down, 5’-CGGAGTAGTATTTATCACAATATC-3’ (20). Furthermore, we used an alternative forward primer for undetected trpB of BCC: trpE-F2, 5’-AAGGACGCGCTGAACGAAGC-3’. The alternative primers used for the undetected tpiA of S. epidermidis were as follows: tpi-DF, 5’- GCAAGTATTTGGATAAAAGC-3’; tpi-DR, 5’- CCATCTAAGATGATTAAGGC-3’. The allele numbers and STs of each isolate were assigned according to the MLST database (https://pubmlst.org/). We performed advanced cluster analysis to define clonal complexes (CCs) by using BioNumerics software ver. 7.6 (Applied Maths, Sint-Martens-Latem, Belgium).