Levofloxacin

Eleven carbapenem resistance genes (bla_IMP, bla_VIM, bla_NDM, bla_SPM, bla_AIM, bla_DIM, bla_GIM, bla_SIM, bla_KPC, bla_BIC, and bla_OXA–48) (Poirel et al., 2011 (link)) were screened using PCR detection from the presumptive carbapenemase-producing bacteria. The amplicons were sequenced (Macrogen) and identified using NCBI BLAST¹. For the screened carbapenemase-producing bacteria, MDR to 16 antibiotics was determined using Kirby-Bauer disk diffusion, and resistance to colistin was determined using broth dilution methods. For MDR, the following antibiotic disks were used: ampicillin-sulbactam (10/10 μg), cefotaxime (30 μg), ceftazidime (30 μg), chloramphenicol (30 μg) ciprofloxacin (5 μg), colistin (2 mg/L), doripenem (10 μg), fosfomycin (200 μg), gentamicin (10 μg), levofloxacin (5 μg), meropenem (10 μg), netilmicin (10 μg), piperacillin (100 μg), tetracycline (30 μg), tobramycin (10 μg), and trimethoprim-sulfamethoxazole (1.25/23.75 μg) (Liofilchem, Roseto degli Abruzzi, Italy). Resistance to the antibiotics was determined according to the Clinical and Laboratory Standards Institute (CLSI) guideline (Clinical Laboratory Standars and Institue, 2016 ). Subsequently, MICs of 16 antibiotics for E. coli strain N7 were evaluated using the broth dilution method (Hasselmann, 2003 (link)).

Antimicrobial susceptibility testing for clinical isolates was determined by the Kirby–Bauer disc diffusion method on Mueller–Hinton agar plates at 37°C for 20–24 hours, according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI 2022). The McFarland 0.5 standard was used to standardize the inoculum density for susceptibility tests [23 ]. The antibiotic discs used in the current study included TMP-SMX (1.25/23.75 μg), levofloxacin (5 μg), and minocycline (30 μg) (Liofilchem, Italy). E. coli ATCC 25922 was used as the control to check the accuracy of the susceptibility testing.