Azithromycin

Ampicillin (Amp) and cefoperazone (CPZ) were acquired from the General Pharmaceutical Factory of Harbin Pharmaceutical Group (Harbin, China). Roxithromycin (ROX), chloramphenicol (CHL) and azithromycin (AZM) were from Sangon Biotech Co., Ltd. (Shanghai, China). Amikacin (AMK), vancomycin (VAN), levofloxacin (LVX) and polymyxin (PB) were from Sigma-Aldrich Co. LLC (Sigma, St. Louis, MO, USA).

The bacteria isolate was used for antimicrobial susceptibility testing (AST) against 17 antimicrobial agents. Broth microdilution minimum inhibitory concentration (MIC) determination was performed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines and interpretation (CLSI, 2018 ), the European Committee for Antimicrobial Susceptibility Testing (EUCAST, 2018 ), and where no EUCAST or CLSI interpretative criteria were available, breakpoints were harmonized with those of the National Antimicrobial Resistance Monitoring System (NARMS), United States (FDA, 2017 ). The following antimicrobials were tested: fosfomycin, levofloxacin, cefoperazone sulbactam, streptomycin, ampicillin, amoxicillin–clavulanic acid, cefoxitin, imipenem, nalidixic acid, ciprofloxacin, chloramphenicol, tetracycline, kanamycin, gentamicin, trimethoprim–sulfamethoxazole, ceftiofur, and azithromycin (Sangon Biotech, China). Escherichia coli ATCC 25922 were used as a control strain. The AST against all antibiotics were carried out in Muller–Hinton broth (MHB) medium in both aerobic and anaerobic conditions and incubated at 37°C. The AST was also performed in Dulbecco’s modified Eagle’s medium (DMEM) (Dulbecco and Freeman, 1959 (link)) and incubated in a 5% CO₂ incubator.