Risk Factors Associated with Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae Nosocomial Bloodstream Infections in a Tertiary Care Hospital: A Clinical and Molecular Analysis

Abstract

Aim: To describe the risk factors and molecular epidemiology of nosocomial bloodstream infections caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in a tertiary care hospital. Methods: Patients with enterobacteria-positive blood cultures were included. ESBL expression in the isolates was detected using the combination disk method. Antimicrobial susceptibility testing was performed using the disk diffusion method. bla_SHV, bla_TEM, and bla_CTX-M genes were identified in the isolated strains by PCR and sequencing. Klebsiella pneumoniae isolates were genotyped by PFGE. Results: Of the 90 isolates recovered, half were found to express ESBLs. Twenty-eight (62%) of these isolates were K. pneumoniae, 8 (18%) were Escherichia coli, 6 (13%) were Enterobacter cloacae, and 3 (7%) were Serratia marcescens. Multivariate logistic regression analysis showed that the only independent risk factor associated with infection by ESBL-producing strains was use of broad-spectrum cephalosporins. None of the isolates was resistant to imipenem. The bla_SHV5 gene was detected in 84% of isolates, followed by bla_CTX-M15 (27%), bla_SHV2 (9%), and bla_SHV12 (7%). PFGE identified six clones among the 28 ESBL-producing K. pneumoniae isolates. Conclusions: ESBL-producing K. pneumoniae clones were detected throughout the hospital. Use of broad-spectrum cephalosporins is the most important risk factor associated with the proliferation of ESBL-producing strains.