Netilmicin

The isolates were initially processed using disk-diffusion antimicrobial susceptibility testing for amikacin, aztreonam, cefepime, ceftazidime, ciprofloxacin, doripenem, gentamicin, imipenem, levofloxacin, meropenem, netilmicin, piperacillin-tazobactam, ticarcillin-clavulanate, and tobramycin with Oxoid (Basingstoke, United Kingdom) disks. Complementarily, an in-house broth microdilution method using cation-adjusted Mueller–Hinton Broth (Sigma-Aldrich, St. Louis, MO, USA) was performed to determine the minimum inhibitory concentration (MIC) for amikacin gentamicin, imipenem, meropenem, colistin, polymyxin B, tigecycline, and ceftazidime-avibactam, and all salts were purchased from Sigma-Aldrich (St. Louis, MO, USA), except for avibactam, which was donated by Pfizer Inc. To complete the antimicrobial susceptibility panel, novel antimicrobials/combinations were evaluated with Liofilchem (Roseto degli Abruzzi, Italy) MIC test strips for ceftolozane–tazobactam, meropenem–vaborbactam, imipenem–relebactam, cefoperazone–sulbactam, cefiderocol, plazomicin, eravacycline, and fosfomycin.

The samples obtained were cultured on bloody agar and EMB agar, and conventional methods plus a VITEK-2 Compact Automated System (bioMerieux, Marcy-l’Etoile, France) were used for bacterial identification and antibiograms. The antibiotic susceptibility of the isolated strains was determined by the Kirby Bauer disk diffusion method (CLSI 2010) [18 ]. Ampicillin-sulbactam (10/10 μg), piperaciline-tazobactam 100/10 μg, cefepime (30 μg), ceftazidime (30 μg), imipenem (10 μg), meropenem (10 μg), gentamicin (10 μg), amikacin (30 μg), tobramicin (10 μg), netilmicin (30 μg), trimethoprim/sulfamethoxazole (1.25 μg/23 μg), ciprofloxacin (5 μg), colistin (10 μg), and tigecycline (15 μg) antibiotic disks (Oxoid, UK) were used. P.aeruginosa ATCC 27853 was studied as the quality control strain. For colistin, the interpretive criteria of Galani et al. [19 (link)], and for tigecycline, the interpretive criteria of Jones et al. [20 (link)], were applied. The imipenem-resistant strains were detected by the disk diffusion method and confirmed by the imipenem E-test (Oxoid M.I.C Evaluator, UK).