부산대학교 도서관

Objective: Some carbapenem-nonsusceptible Klebsiella pneumoniae (CnSKP) isolates are susceptible to β-lactams of narrower spectra. However, their clinical significance and molecular characterization are unknown. Methods: CnSKPs were screened, and antimicrobial susceptibility test results were retrieved in the database of clinical microbiology laboratory from 2004 to 2019. Patient characteristics and outcomes were collected from the medical records. Polymerase chain reaction forβ-lactamases and pulsed-field gel electrophoresis (PFGE) were performed. Results: The overall prevalence of CnSKP was 0.96% (197/20,465). At least 37 of the 197 isolates remained susceptible to β-lactams of narrower spectra, and a total of 34 CnSKP isolates were included. Carbapenemase genes were detected in nine isolates (26.5%), three of which were bla_(KPC), bla_(IMP-2), and bla_(NDM). A few isolates remained susceptible to β-lactams of narrower spectra, such as cefazolin (5.9%), ceftriaxone (5.9%), ceftazidime (5.9%), cefmetazole (11.8%), cefepime (26.5%), and piperacillin-tazobactam (20.6%). All these isolates had a meropenem minimum inhibitory concentration (MIC) ranging from 2 to 4 mg/L and were susceptible to ceftazidime-avibactam. All these bacteria harbored extended-spectrum β-lactamase (ESBL) genes, and none had carbapenemase genes. The treatment outcomes of patients who carried these bacteria were not associated with appropriate antibiotic use but with the site of isolation. Hospital-acquired infection, nonsusceptibility to cefepime, and meropenem MIC ≥ 16 mg/L were associated with the detection of carbapenemase genes and 14-day mortality in univariate analyses. PFGE results suggested that carbapenemase genes disseminated more readily than ESBL and AmpC β-lactamase genes. Conclusions: The CnSKP composition is complex. Carbapenemase-producing Klebsiella pneumoniae (CPKP) strains have different characteristics from non-CPKP strains.