Molecular characterization and survival of extended-spectrum β-lactamase-producing clinical strains of Klebsiella pneumoniae isolated in Mostar, Bosnia and Herzegovina.

The aim of this retrospective study was to investigate the molecular characteristics and survival ability of clinical isolates of extended-spectrum β-lactamase (ESBL)-producing strains of Klebsiella pneumoniae (K. pneumoniae) in a hospital setting. ESBL-producing K. pneumoniae clinical isolates were collected from hospitalized patients at the University Clinical Hospital of Mostar, Bosnia and Herzegovina. Identification and antibiotic susceptibility tests were performed according to established laboratory methods and Clinical and Laboratory Standards Institute standards. Phenotypic identification of the isolates was confirmed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Minimum inhibitory concentrations were determined using the Vitek® 2 Compact System. Clonal relationships between the different isolates were studied using pulsed-field gel electrophoresis. Molecular characterization of ESBL-coding genes was performed using multiplex polymerase chain reaction. The survival and pellicle formation abilities of ESBL-producing K. pneumoniae isolates were also investigated. Among 471 isolated K. pneumoniae strains, 149 isolates (31.6%) were ESBL-producing. The bla genes encoding CTX-M-1-group ESBLs were identified in almost all isolates, with the majority carrying blaCTX-M-15. Two isolates contained blaCTX-M-3. All isolates carried blaTEM-1. The blaSHV genes identified were blaSHV-1, blaSHV-5, blaSHV-11, and blaSHV-28. Six isolates harbored blaOXA-1. ESBL-producing K. pneumoniae strains survived on dry cotton for up to 49 days.