Abstract
Objective: Extended-spectrum beta-lactamase (ESBL)-producing Gram negative bacteria are an emergent cause of urinary tract infections in nonhospitalized patients in different countries. Studies on ESBLs in the outpatient populations reported CTX-M ESBLs to be the most prevalent. The aim of this study was the molecular characterization of ESBL-producing K. pneumoniae strains isolated from urine of outpatients in Zagreb region during the last five years. Methods: During the five-year study period a total of 2, 651 K. pneumoniae strains were isolated from urine of nonhospitalized patients with significant bacteriuria. ESBL production was detected by double-disk diffusion technique and by >3-dilution reduction in the minimal inhibitory concentration of ceftazidime in the presence of clavulanate. A total of 441 ESBL-producing K. pneumoniae strains (15.5%) were collected and 25 strains were characterised. Characterization of ESBLs was performed by PCR with specific primers for ESBLs and by sequencing of blaESBL genes. Results: A significant difference in frequencies of ESBL isolates was observed. In the first year of study only 4.9% of isolated strains were ESBL producers, while in the second year 17.3% ESBL strains were detected (p<0.01), and the frequency remain stabile within following years. Out of 25 characterized strains all strains yielded an amplicon with primers specific for SHV beta-lactamases. Five strains possessed an additional TEM beta-lactamase, and 11 strains possessed CTX-M beta-lactamases. Based on sequencing of blaCTX-M genes, enzymes of nine strains were identified as CTX-M 1 beta-lactamase. Conclusion: The study demonstrated community-associated emergence of CTX-M 1 beta-lactamase– producing K. pneumoniae strains. Further studies are necessary to investigate the possibility of clonal dissemination and hospital origin of those strains.
Published Version
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