Characterization of Escherichia coli and Klebsiella pneumoniae with resistance or reduced susceptibility to carbapenems isolated from Canadian hospitals from 2007-2010

Abstract

Escherichia coli and Klebsiella pneumoniae isolates were obtained from the Canadian Ward Surveillance Study (CANWARD) and underwent in vitro susceptibility testing to determine prevalence and antimicrobial resistance patterns. The prevalence was found to be relatively stable over the years although there was an increase in prevalence among the K. pneumoniae isolates; 1.1% to 1.3% to 2.5% to 2.6% in 2007, 2008, 2009, and 2010, respectively. Genotypic characterization was conducted on ESBL, AmpC, carbapenemase genes, and outer membrane porins. The highest proportion of isolates were found to produce CTX-M-15 β-lactamase. Only 1 of each KPC-producing E. coli and K. pneumoniae was found. Porin alteration was found to be a factor leading to carbapenem reduced susceptibility among isolates. Genetic relatedness of CRS/CIR E. coli and K. pneumoniae was determined using pulsed-field gel electrophoresis. The spread of these organisms was mainly due to polyclonal spread rather than one specific clone.