Cefepime

The antimicrobial susceptibility of the isolates to 17 antimicrobial agents was determined on Mueller–Hinton agar (Oxoid, UK) using the Kirby Bauer disc diffusion method, according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI, 2020). The tested antimicrobial agents (Bioanalyse, Turkey) included Amoxicillin/clavulanate (30 µg), cefepime (30 µg), cefotaxime (30 µg), cefoxitin (30 µg), ceftriaxone (30 µg), ceftazidime (30 µg), aztreonam (10 µg), imipenem (10µg), amikacin (30 µg), gentamicin (10 µg), ciprofloxacin (5 µg), tetracycline (30 µg), trimethoprim 1.25 µg/sulphamethoxazole 23.75 µg (SXT, 25 µg), chloramphenicol (30 µg), nitrofurantoin (300 µg), and tigecycline (15 µg). The broth microdilution assay was used to determine the minimum inhibitory concentrations (MICs) of colistin. The breakpoints proposed by the European Committee on Antimicrobial Susceptibility Testing [34 ] were used for interpreting the antimicrobial susceptibility tests of tigecycline and colistin. MDR and XDR phenotypes were inferred according to the definitions of Magiorakos et al. [35 (link)].

Raw materials of antibiotics of doripenem, tigecycline, and tetracycline were provided by Cayman Chemical Company (Michigan, USA) and cefepime was provided by Demo S.A. Pharmaceutical (Votanikos, Greece). doripenem and cefepime were suspended in saline while tigecycline and tetracycline were suspended in distilled water. The antibiotic disks of tigecycline (15 µg), doripenem (10 µg), oxacillin (1 µg), and cefoxitin (30 µg) were provided by Oxoid (Hampshire, UK), while cefepime (30 µg) and tetracycline (30 µg) were provided by Bioanalyse (Ankara, Turkey). The antibiotic E-strips of tigecycline (0.016-256 µg/ml), tetracycline (0.016-256 µg/ml), cefepime (0.016-256 µg/ml), oxacillin (0.016-256 µg/ml), cefoxitin (0.016-256 µg/ml), and doripenem (0.002-32 µg/ml) were provided by HiMedia (Mumbai, India).

Antimicrobial susceptibility of the isolates was performed by the disk diffusion method according to the instructions of CLSI [30 ] using Mueller-Hinton agar (HIMEDIA, India). The used antimicrobials were obtained from Bioanalyse/ Turkey and included: ampicillin (AMP: 10 μg); amoxicillin-clavulanic acid (AMC: 20/10 μg); cefoxitin (FOX: 30 μg); cefotaxime (CTX: 30 μg); ceftazidime (CAZ: 30 μg); ceftriaxone (CRO: 30 μg); cefepime (FEP: 30 μg); aztreonam (ATM: 30 μg); imipenem (IPM: 10 μg); meropenem (MEM: 10 μg); gentamicin (CN: 10 μg); amikacin (AK: 30 μg); tetracycline (TE: 30 μg); nalidixic acid (NA: 30 μg); ciprofloxacin (CIP: 5 μg); trimethoprim-sulfamethoxazole (SXT: 1.25/23.75 μg); and nitrofurantoin (F: 300 μg).