Characterization of Extended-Spectrum Cephalosporin–ResistantSalmonella entericaSerovar Heidelberg Isolated from Humans in the United States

Abstract

During the past decade, extended-spectrum cephalosporin resistance has increased among human isolates of Salmonella enterica serovar Heidelberg, the fourth most common serotype in the United States. We therefore characterized 54 Heidelberg isolates with decreased susceptibility (minimum inhibitory concentrations >or=2 mg/L) to ceftriaxone or ceftiofur; 49 (90.7%) contained the CMY-type beta-lactamase (bla(CMY)) gene. The 49 bla(CMY)-positive human Heidelberg isolates demonstrated a high degree of relatedness; 4 clusters (25 isolates total) had indistinguishable XbaI and BlnI patterns by pulsed-field gel electrophoresis and were indistinguishable from 42 retail meat Heidelberg isolates. Further characterization of 15 of these isolates demonstrated that all of the bla genes were bla(CMY-2) and plasmid-encoded, and most (11/15) of the plasmids were approximately 100 kb in size and belong to the incompatibility group I1 (IncI1). All five IncI1 plasmids tested by plasmid multilocus sequence typing analysis were ST12. This report suggests that extended-spectrum cephalosporin resistance among human Heidelberg isolates is mediated by the spread of a common IncI1 bla(CMY-2) plasmid, which may have a preference for a particular genetic background.

Comparison of the Prevalences and Antimicrobial Resistances of Escherichia coli Isolates from Different Retail Meats in the United States, 2002 to 2008

“…In the last 10 years, this resistance phenotype has emerged in both humans and food animals in the United States (12,40,44). TIO is the only cephalosporin approved for systemic use in food animals in the United States.…”

Scientific Opinion on the public health risks of bacterial strains producing extended-spectrum β-lactamases and/or AmpC β-lactamases in food and food-producing animals

“…(Cloeckaert et al, 2007) Infantis bla Poultry, Swine Yes France, Belgium, Japan (Cloeckaert et al, 2007;Dahshan et al, 2010;Yang et al, 2010) Virchow bla CTX-M-2 , bla CTX-M-9 Poultry Yes Spain, France (Bertrand et al, 2006;Riano et al, 2009;Riano et al, 2006;Weill et al, 2004). Westhampton/ Senftenberg bla Cockles No French supermarkets (Doublet et al, 2009) Heidelberg bla CMY-2 Imported live animals, meat consumption, unpasteurized dairy products Yes EU, USA Folster et al, 2009 (Carattoli, 2009;Golebiewski et al, 2007) IncHI2…”

“…Heidelberg and Newport producing CMY-2, and also of S. Typhimurium have similarly been documented . Outbreaks of CMY-2 producers due to clonal expansion of S. Heidelberg caused by imported live animals, meat consumption and unpasteurized dairy products were described in the EU and the US Folster et al, 2009;Zhao et al, 2008). Human infections by S. Newport lineage II comprises most of MDR-AmpC clones of this serotype, which are linked to ST45 (and single locus variant ST116) and associated with consumption of cattle, bovine, and horse meat or pets treats (Espie and Weill, 2003;Harbottle et al, 2006;Pitout et al, 2003;Sangal et al, 2010).…”

Comparison of Salmonella enterica Serovar Heidelberg Isolates from Human Patients with Those from Animal and Food Sources

“…Antimicrobial-resistant S. Heidelberg strains have been isolated from humans, retail meats, and food animals (13-15, 17, 18, 24); thus, resistant organisms in the food supply may contribute to human disease. Multiple studies have examined the genetics of antimicrobial resistance in S. Heidelberg isolates from food animals; however, information on those isolated from human patients is limited (6,19). The goal of this study was to characterize antimicrobial resistance and associated genetic factors in S. Heidelberg from humans and compare these results to those obtained with previously characterized isolates from food and food animal sources (13,15).…”