Detection and genotype analysis of AmpC β-lactamase in Klebsiella pneumoniae from tertiary hospitals

The aim of the present study was to investigate the phenotype and genotype of plasmid‑mediated AmpC (pAmpC) β‑lactamase in Klebsiella pneumoniae and its antibiotic resistance. A total of 130 non‑repetitive clinical isolates of Klebsiella pneumoniae, obtained from tertiary hospitals, were phenotypically screened for pAmpC β‑lactamase production with the cefoxitin disk diffusion test. β‑lactamase genes in the screened isolates were detected using multiplex polymerase chain reaction (PCR); carbapenemase genes in pAmpC β‑lactamase‑producing isolates that were resistant to imipenem were detected using PCR. Out of the 130 isolates of Klebsiella pneumoniae, 62 strains (47.7%) were resistant to cefoxitin, including 14 strains (10.8%) positive for pAmpC β‑lactamase (DHA type), among which 12 strains (85.7%) were susceptible to imipenem, and 2 strains, which were carrying Klebsiella pneumoniae carbapenemase (KPC)‑2 gene, were resistant to imipenem. The pAmpC β‑lactamase‑producing Klebsiella pneumoniae isolates from the tertiary hospitals were mainly of DHA‑1 genotype, and the majority were susceptible to carbapenems; drug‑resistant strains were associated with KPC‑2 expression.