Rifampin

Antibiotic susceptibility was measured with the use of the standard disc diffusion process suggested by the Clinical and Laboratory Standards Institute (CLSI) guidelines by broth microdilution and E-test (cat. nos. 537300, 501800, 533500, 501300, 501600, 506710, 513800, 526000, 523600, 525508, 522000, 503500 and 521400; AB Biodisk; BioMérieux Inc.) (17 ). A total of 14 antibiotics were tested, including ampicillin-sulbactam, trimethoprim-sulfamethoxazole, aminoglycoside antibiotic amikacin, macrolide antibiotic azithromycin, β-lactam antibiotic aztreonam, β-lactamase inhibitor tazobactam, cephalosporin antibiotics ceftazidime and cephalothin, rifampin and tigecycline, carbapenem antibiotic meropenem and colistin, and the glycopeptide antibiotics teicoplanin and vancomycin (Bio-Rad, Laboratories, Inc., Hercules, CA, USA). These antibiotics are of different classes and have different killing mechanisms on the bacteria. The E-test technique was used to determine the minimum inhibitory concentrations (MICs) of meropenem. The results were interpreted according to the CLSI guidelines from 2015 (18 ).