Antimicrobial Susceptibility Testing

Antibiotic resistance profiles were determined by minimum inhibitory concentrations (MICs) using VITEK 2 COMPACT microbiology system (BioMérieux, France). Breakpoint interpretation was done according to the criteria of the Clinical and Laboratory Standards Institute (CLSI), 2020 Edition (CLSI, 2020). A double-disk agar diffusion test (D-test) was performed to detect the inducible macrolide–lincosamide–streptogramin B phenotype. Streptococcus pneumoniae ATCC 49619 and Staphylococcus aureus ATCC25923 were used as quality controls. Antimicrobial agents containing erythromycin, clindamycin, tetracycline, levofloxacin, penicillin, ampicillin, vancomycin, tigecycline, and linezolid were tested against all isolates. An FQ-resistant isolate was defined as a levofloxacin minimum inhibitory concentrations (MIC) >8 mg/L. An MDR isolate was defined as resistance to at least two of the antimicrobial agent classes above in addition to levofloxacin.