Emergence of bla SHV-12 and qnrS1 encoded on IncX3 plasmids: Changing epidemiology of extended-spectrum ß-lactamases among Enterobacterales isolated from broilers.

Objectives: The occurrence of extended-spectrum ß-lactamase (ESBL)-producing Enterobacterales in broilers represents a risk to public health because of the possibility of transmission of ESBL producers and/or bla _ESBL genes via the food chain or within settings where human-animal interfaces exist.
Methods: This study assessed the occurrence of ESBL producers among faecal samples of broilers at slaughter. Isolates were characterised by multilocus sequence typing, antimicrobial susceptibility testing, and whole-genome sequencing.
Results: The flock prevalence, determined by sampling crates of 100 poultry flocks, was 21%. The predominant bla _ESBL gene was bla _SHV-12 , identified in 92% of the isolates. A variety of Escherichia coli and Klebsiella pneumoniae sequence types (STs) were identified, including extraintestinal pathogenic E. coli ST38, avian pathogenic E. coli ST10, ST93, ST117, and ST155, and nosocomial outbreak clone K. pneumoniae ST20. Whole-genome sequencing was used to characterise a subset of 15 isolates, including 6 E. coli, 4 K. pneumoniae, 1 Klebsiella grimontii, 1 Klebsiella michiganensis, 1 Klebsiella variicola, and 1 Atlantibacter subterranea. Fourteen isolates carried identical or closely related 46338-54929 bp IncX3 plasmids encoding bla _SHV-12 and qnrS1. One E. coli isolate carried a 46338 bp IncX3 plasmid, which was integrated chromosomally into ydbD.
Conclusions: The bla _SHV-12 gene has replaced the previously predominant bla _CTX-M-1 in ESBL-producing Enterobacterales from broilers in Switzerland. Broilers may play a role in the dissemination of bla _SHV-12 and qnrS1 associated with epidemic IncX3 plasmids, representing a risk to human and animal health.
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