title: Molecular characteristics of extended-spectrum-beta-lactamase-producing Escherichia coli isolates causing bacteremia in the Calgary Health Region from 2000 to 2007: emergence of clone ST131 as a cause of community-acquired infections.
abstract: A study was designed to characterize extended-spectrum-beta-lactamase (ESBL)-producing Escherichia coli isolates causing bacteremia over an 8-year period (2000 to 2007) in a large well-defined geographical region. Molecular characterization was done by using isoelectric focusing; PCR; and sequencing of the bla(CTX-M)-, bla(TEM)-, bla(OXA)-, bla(SHV)-, and plasmid-mediated quinolone resistance determinants. Genetic relatedness was determined by pulsed-field electrophoresis with XbaI and multilocus sequence typing. A total of 67 patients with incident bloodstream infections were identified, and the majority presented with community-acquired infections involving the urinary and biliary tracts. Of the 67 ESBL-producing E. coli isolates recovered, 60 (90%) were positive for bla(CTX-M) genes; 32 (48%) produced CTX-M-15, 25 (37%) produced CTX-M-14, 1 (2%) produced CTX-M-24, 1 (2%) produced CTX-M-2, and 1 (2%) produced CTX-M-3, while 2 (3%) produced TEM-52 and 5 (7%) produced SHV-2. Twenty-four (36%) isolates were positive for aac(6')-Ib-cr. The majority of isolates were resistant to ciprofloxacin (60 [90%] isolates) and gentamicin (40 [60%] isolates). The occurrence of ESBL-producing isolates was stable during the first 5 years, but there was a substantial increase from 2005 to 2007, mostly due to clone ST131, which produces CTX-M-15 and CTX-M-14, in blood cultures submitted from the community. Our results illustrated that E. coli clone ST131, which coproduces CTX-M-15, OXA-1, TEM-1, and aac(6')-Ib-cr, has emerged as an important cause of community-onset bacteremia caused by ESBL-producing E. coli isolates; and this is the first study to identify CTX-M-14 in E. coli clone ST131.
authors.affiliation: Division of Microbiology, Calgary Laboratory Services, #9, 3535 Research Road NW, Calgary, Alberta, Canada. johann.pitout@cls.ab.ca
authors.forename: Johann D D
authors.initials: JD
authors.lastname: Pitout
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Gregson
authors.forename: Lorraine
authors.initials: L
authors.lastname: Campbell
authors.forename: Kevin B
authors.initials: KB
authors.lastname: Laupland
mesh_terms: D016470:Bacteremia / Q000382:microbiology*; D017714:Community-Acquired Infections / Q000382:microbiology*; D018432:Drug Resistance, Multiple / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D004927:Escherichia coli Infections / Q000382:microbiology*; D006801:Humans; D016133:Polymerase Chain Reaction; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: C071167:beta-lactamase CTX-2; C456080:beta-lactamase CTX-M-14; C473109:beta-lactamase CTX-M-15; C417271:beta-lactamase CTX-M-3; D001618:beta-Lactamases