MICs of aminoglycosides (amikacin, gentamicin, tobramycin, apramycin, neomycin, paromomycin, and streptomycin), ciprofloxacin, imipenem, meropenem, piperacillin-tazobactam and trimethoprim-sulfamethoxazole were determined using broth microdilution following the recommendations of the Clinical Laboratory Standards Institute (CLSI) (CLSI, 2017 ). Concentrations of these agents ranged from 0.5 to 256 μg/ml except for trimethoprim-sulfamethoxazole. Escherichia coli ATCC 25922 was used as the quality control and all tests were performed in triplicate. Breakpoints defined by CLST for amikacin, gentamicin and tobramycin (for amikacin, susceptible [S] ≤16 μg/ml, intermediate [I] 32 μg/ml, resistant [R], ≥64 μg/ml; for gentamicin and tobramycin, S ≤4 μg/ml, I 8 μg/ml, R ≥16 μg/ml), ciprofloxacin, imipenem, meropenem, piperacillin-tazobactam and trimethoprim-sulfamethoxazole (CLSI, 2017 ) was used, while no CLSI- or the European Committee on Antimicrobial Susceptibility Testing (EUCAST)-defined breakpoints for the other four agents are available. Breakpoints defined by US Food and Drug Administration (FDA) or the National Antimicrobial Resistance Monitoring System were used for streptomycin (S, ≤32 μg/ml; R, ≥64 μg/ml) and apramycin (S, ≤8 μg/ml; I, 16 or 32 μg/ml; R, ≥64 μg/ml) (Smith and Kirby, 2016 (link)), respectively. Those defined by Comite de L'Antibiogramme de la Société Française de Microbiologie (http://www.sfm-microbiologie.org/ ) were used for neomycin and paromomycin (S, ≤8 μg/ml; R, >16 μg/ml; for both agents).
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