Frequency assessment of β-lactamase enzymes in E. coli and Klebsiella isolates in patients with urinary tract infection

Production of β-lactamase enzymes is the most common and important mechanism of resistance in Gram-negative bacteria. Th e objective of this study was to assess frequency of three main β-lactamase enzymes, including extended spectrum β-lactamases (ESBLs), metallo-β-lactamase (MBL), and Klebsiella pneumoniae carbapenemase (KPC) enzymes in Escherichia coli and Klebsiella spp. isolated from nosocomial and community urinary tract infections (UTI).

In a cross-sectional study from March to December 2012, midstream urine samples were obtained from patients suspicious of UTI who were hospitalized or referred to Al-Zahra Hospital, Isfahan, Iran. Samples were cultured and E. coli and Klebsiella spp. were isolated. Prevalence of ESBLs, KPC, and MBLs producing E. coli and Klebsiella spp. were studied by double-disk (combined-disk), the modifi ed Hodge test and imipenem-ethylenediaminetetraacetic acid combined disc methods respectively. In addition, their antimicrobial susceptibility patterns determined and resistant to carbapenem drugs confi rmed by minimum inhibitory concentrations based on E-test method.

A total of 1080 E. coli and 484 Klebsiella strains were isolated during study period. Among 720 E. coli and 384 Klebsiella isolates from hospitalized patients, 300 (41.7%) and 198 (51.5%) were ESBLs producers, respectively. In out-patients samples, the rate of ESBLs production was 25% (90/360) and 40% (40/100) in E. coli and Klebsiella isolates, respectively. Prevalence of MBLs producing in hospital E. coli and Klebsiella isolates were 0.3% (2/720) and 2.6% (10/384), and for KPC data were 1.4% (10/720) and 48.4% (186/384), respectively. No MBLs and KPC producing isolate was seen in non-hospital E. coli and Klebsiella isolates except for one non-hospital KPC producing Klebsiella isolate.

Th e result of our study showed high prevalence of ESBLs and KPC, but low prevalence of MBLs in cultured bacteria from urine samples of patients with acute UTI. In addition, KPC was the main carbapenem resistance mechanism in Klebsiella and E. coli isolates.