Heider LC, Hoet AE, Wittum TE, Khaitsa ML, Love BC, Huston CL, Morley PS, Funk JA, Gebreyes WA.
The bla(CMY-2) family of the ampC beta-lactamase genes confer broad-spectrum resistance to beta-lactam antimicrobials, including ceftriaxone and ceftiofur, as well as to beta-lactamase inhibitors, such as clavulanic acid. Organisms with the bla(CMY-2) phenotype have been recovered from the environment and from retail meat products, posing a potential public health risk. The objectives of this study were to sequence the bla(CMY-2) gene from Escherichia coli and Salmonella enterica from multiple sources that had a reduced susceptibility to ceftriaxone and to determine the effect of observed mutations in the bla(CMY-2) gene on the antimicrobial resistance phenotype (spectrum and minimum inhibitory concentration/susceptibility patterns) of the isolates. The bla(CMY-2) genes from 52 bacterial isolates were sequenced for this study. Sixty-two percent (32/52) were E. coli and 38% (20/52) were S. enterica. Of the 32 E. coli isolates, 30 were found to carry a beta-lactamase gene that was 100% homologous to bla(CMY-2). One of the E. coli isolates was found to contain a gene that was 90% homologous to bla(CMY-2). This isolate also had lower minimum inhibitory concentrations to tetracyclines, streptomycin, and the sulfonamide antimicrobials than are commonly expected for isolates containing the bla(CMY-2). Of the 20 genes obtained from Salmonella isolates, 8 (40%) were found to be homologous to bla(CMY-2), with no altered susceptibility phenotypes observed.
Heider LC, Hoet AE, Wittum TE, Khaitsa ML, Love BC, Huston CL, Morley PS, Funk JA, Gebreyes WA. Genetic and phenotypic characterization of the bla(CMY) gene from Escherichia coli and Salmonella enterica isolated from food-producing animals, humans, the environment, and retail meat. Foodborne Pathog Dis. 2009 Dec;6(10):1235-40. doi: 10.1089/fpd.2009.0294.