Detection of CTX-M-1 extended-spectrum beta-lactamase among ceftiofur-resistant Salmonella enterica clinical isolates of poultry

Thomas N. Denagamage, Eva Wallner-Pendleton, Bhushan M. Jayarao, Lingzi Xiaoli, Edward G. Dudley, David Wolfgang, Subhashinie Kariyawasam

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4 Scopus citations


Salmonella enterica resistance to extended-spectrum cephalosporins (ESC) conferred by cefotaximases (blaCTX-M) is a growing concern in the United States. Among food-producing animals, poultry are a major reservoir of ESC-resistant Salmonella. A retrospective study was carried out to further characterize 38 ceftiofur-resistant clinical Salmonella enterica isolates obtained from poultry during 2007–2018. Of the isolates tested, 31 displayed resistance to ceftriaxone and harbored blaCMY-2, whereas 7 isolates demonstrated resistance or reduced susceptibility to cefepime in addition to ceftriaxone resistance. These 7 isolates displayed extended-spectrum β-lactamase activity, harbored blaCTX-M-1, and were recovered only from recent poultry diagnostic submissions made in 2011–2018 as opposed to the 31 isolates that were recovered in 2007–2018. Further characterization of the blaCTX-M-1 gene determined that it was located on conjugative IncN/ST1 and IncI1/ST87 plasmids in the isolates from commercial turkeys and broilers, respectively. These plasmids have been responsible for extensive spread of blaCTX-M-1 in livestock, poultry, and humans in Europe. Potential transfer of IncN and IncI1 plasmids and/or nontyphoidal Salmonella carrying these plasmids through the food chain, or by other means to humans, may result in treatment failures. Our study demonstrates the importance of further characterization of ceftiofur-resistant S. enterica isolates detected by veterinary diagnostic laboratories to identify the sources of blaCTX-M-1 and to mitigate the spread of ESC-resistant Salmonella in the poultry production pyramid.

Original languageEnglish (US)
Pages (from-to)681-687
Number of pages7
JournalJournal of Veterinary Diagnostic Investigation
Issue number5
StatePublished - Sep 1 2019

All Science Journal Classification (ASJC) codes

  • General Veterinary


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