Characterization of E. Coli isolates producing extended spectrum beta-lactamase SHV-variants from the food chain in Germany

Resistance of bacteria to 3^rd generation cephalosporins mediated by beta-lactamases (ESBL, pAmpC) is a public health concern. In this study, 1517 phenotypically cephalosporin-resistant E. coli were screened for the presence of blaSHV genes. Respective genes were detected in 161 isolates. Majority (91%) were obtained from poultry production and meat. The SHV-12 beta-lactamase was the predominant variant (n = 155), while the remaining isolates exhibited SHV-2 (n = 4) or SHV-2a (n = 2). A subset of the isolates (n = 51) was further characterized by PCR, PFGE, or whole-genome sequencing and bioinformatics analysis. The SHV-12-producing isolates showed low phylogenetic relationships, and dissemination of the bla_SHV₋₁₂ genes seemed to be mainly driven by horizontal gene transfer. In most of the isolates, bla_SHV₋₁₂ was located on transferable IncX3 (~43 kb) or IncI1 (~100 kb) plasmids. On IncX3, bla_SHV₋₁₂ was part of a Tn6 composite transposon located next to a Tn3 transposon, which harbored the fluoroquinolone resistance gene qnrS1. On IncI1 plasmids, bla_SHV₋₁₂ was located on an incomplete class 1 integron as part of a Tn21 transposon. In conclusion, SHV-12 is widely distributed in German poultry production and spreads via horizontal gene transfer. Consumers are at risk by handling raw poultry meat and should take care in appropriate kitchen hygiene.