Diversity of Plasmids and Genes Encoding Resistance to Extended Spectrum Cephalosporins in Commensal From Dutch Livestock in 2007-2017.

Extended-spectrum β-lactamase (ESBL) and plasmid-mediated AmpC β-lactamase (pAmpC) genes confer resistance to extended spectrum cephalosporin's. The spread of these genes is mostly facilitated by plasmid-mediated horizontal transfer. National surveillance activities to detect ESBL/pAmpC-producers in commensal bacteria from livestock are in place in the Netherlands since several years. This study aimed at reporting gene and plasmid diversity of commensal ESBL/pAmpC-producing isolated from healthy animals during surveillance activities between 2007 and 2017. A collection of 2304 extended-spectrum cephalosporin-resistant (ESC-R) isolated from feces of broilers, dairy cattle, slaughter pigs, turkeys, ducks, and veal calves was investigated and ESBL/pAmpC genes were determined. Gene location of a selection of 473 isolates was determined and typing of plasmids linked to the ESBL/pAmpC genes was performed. Twenty-two different ESBL/pAmpC genes were identified with being the most prevalent gene in livestock (43.7%), followed by and , independent of the animal source. Prevalence of typically human associated was highest in cattle. Less than 10% isolates owed their ESC-R phenotype to promoter mutations of the chromosomal gene. Majority (92%) of ESBL/pAmpC genes analyzed were plasmid located, with IncI1α being the most represented plasmid family in isolates from all animals, followed by IncF (veal calves, dairy cattle and slaughter pigs), IncK (broilers and laying hens), IncX1 in broilers, and emerging IncX3 in broilers and dairy cattle. Prevalence and molecular diversity of ESC-R isolated from livestock over an 11-year period revealed a composite scenario of gene-plasmid combinations.