Characterisation of AmpC and extended-spectrum beta-lactamase producing E. coli from New Zealand dairy farms

Abstract

Dairy farms worldwide have been identified as a source of extended-spectrum β-lactamase (ESBL) and plasmid-mediated AmpC β-lactamase (pACBL) producing Enterobacteriaceae. There is limited data on the prevalence of these antimicrobial resistant bacteria from pasture-based farming systems. We carried out a regional cross-sectional study to examine the prevalence of ESBL and ACBL producing E. coli and characterised the genes responsible for antimicrobial resistance. Paddock faecal swabs were collected from fifteen dairy farms and screened for ESBL- and ACBL-producing E. coli. One farm was positive for ESBL-producing E. coli and three farms were positive for overexpressed chromosomal ampC. The three ESBL-producing E. coli isolates identified were further characterised using Illumina short-read and Oxford Nanopore long-read sequencing technologies. These three E. coli isolates were ST405 and contained an IncFII type plasmid with a blaCTX-M-14 gene. These results suggest the prevalence of ESBL- and pACBL-producing E. coli on pasture-based farms is low.