Detection of ESBLs in Klebsiella spp.

For the detection of ESβLs enzymes in K. pneumoniae strains, the Phoenix M50 System (Becton Dickinson, NJ, USA) with NMIC-408 panels was employed. Meanwhile, for K. variicola isolates, ESβLs enzyme activities were identified using the disc diffusion method, specifically the double-disc synergy test with ceftazidime (30 μg), cefotaxime (30 μg), cefepim (30 μg), and amoxicillin with clavulanic acid (30 μg) (Liofilchem, Abruzzi, Italy). Control strains, including E. coli ATCC 25922 (ESβLs-negative) and K. pneumoniae ATCC 700603 (ESβLs-positive), were utilized. For strains resistant to carbapenems, both the Carbapenem Inactivation Method [19 (link)] and eazyplex^® SuperBug CRE test (Amplex Diagnostics, Gars-Bahnhof, Germany) were employed. Reference strains for this analysis included K. pneumoniae NCTC 13442 (OXA-positive), K. pneumoniae NCTC 13438 (KPC-positive), K. pneumoniae BAA-2146 (NDM-positive), K. pneumoniae NCTC 13440 (VIM-positive), and K. pneumoniae ATCC 700603 (ESβLs-positive).