This was performed with the disk diffusion method (Kirby-Bauer’s) and the inhibition zone diameters were measured by (mm) according to Clinical and Laboratory Standards Institute (CLSI).12 (link) The antimicrobial discs tested include Amoxicillin/clavulanic acid (30 μg), ampicillin (10 μg), cefotaxime (30 μg), ceftazidime (30 μg), ceftriaxone (30 μg), aztreonam (30 μg), imipenem (10 μg), meropenem (10 μg), ertapenem (10 μg), gentamicin (10 μg), tobramycin (10 μg), amikacin (30 μg), tetracycline (30 μg), ciprofloxacin (5 μg), norfloxacin (10 μg), nalidixic acid (30 μg), co-trimoxazole (25 μg) and colistin (10 μg) were obtained from HiMedia Laboratories (India). The results for the antimicrobial susceptibility test strain were interpreted as (S) susceptible, (I) intermediate or (R) resistant by comparing the results to the CLSI 2018 standard zone diameter.12 (link) Minimum inhibitory concentrations (MICs) for imipenem and meropenem were performed by the agar dilution method and interpreted according to CLSI guidelines (strains displaying MICs ≥8 µg/mL for imipenem and meropenem were considered resistant).12 (link)
Escherichia coli ATCC 25922 was used as standard control strains.