RT Journal Article SR Electronic T1 Molecular epidemiology of cefotaxime-resistant Escherichia coli from dairy farms in South West England identifies a dominant plasmid encoding CTX-M-32 JF bioRxiv FD Cold Spring Harbor Laboratory SP 845917 DO 10.1101/845917 A1 Jacqueline Findlay A1 Hannah Schubert A1 Katy Morley A1 Oliver Mounsey A1 Virginia C. Gould A1 Emma F. Puddy A1 Nerissa Newbold A1 Kristen K. Reyher A1 Tristen A. Cogan A1 Matthew B. Avison YR 2019 UL http://biorxiv.org/content/early/2019/11/17/845917.abstract AB Objectives The objective of this study was to identify the mechanisms of cefotaxime resistance (CTX-R) in 1226 Escherichia coli from 4581 environmental samples collected on 53 dairy farms over a 2-year period in South West England and to characterise a blaCTX-M-32-producing plasmid, pMOO-32, found to be widely distributed.Methods CTX-R isolates were identified using MIC breakpoint agar plates. β-lactamase genes of interest (GOIs) were detected by PCR. WGS was performed and analysed using the Center for Genomic Epidemiology platform. A plasmid-specific multiplex PCR was designed to indicate the presence of plasmid pMOO-32.Results Amongst 1226 CTX-R isolates, PCR identified blaCTX-M group 1 (549 isolates), blaCTX-M group 9 (100 isolates), blaCMY (12 isolates), blaDHA (1 isolate) and no GOI (566 isolates). WGS analysis of 184 representative isolates identified blaCTX-M (131 isolates; encoding CTX-M-1, -14, -15, -32 and the novel variant, CTX-M-214), blaCMY-2 (6 isolates), blaDHA-1 (one isolate) and presumed AmpC-hyperproduction in 46 isolates that were PCR negative for GOIs. A highly conserved plasmid was identified in 73 isolates, representing 27 E. coli STs. This ∼220 kb IncHI2 plasmid carrying blaCTX-M-32 was designated pMOO-32, was found to be stable in cattle and human transconjugant E. coli even in the absence of selective pressure, and was found by multiplex PCR to be present on 26/53 study farms.Conclusions β-lactamases capable of conferring resistance to third generation cephalosporins were evident on 47/53 farms within this study. This was largely because of the widespread dissemination of an IncHI2 plasmid carrying blaCTX-M-32.