Characterization of AmpC-hyperproducing Escherichia coli from humans and dairy farms collected in parallel in the same geographical region

Maryam Alzayn, Jacqueline Findlay, Hannah Schubert, Oliver Mounsey, Virginia C Gould, Kate J Heesom, Katy M Turner, David C Barrett, Kristen K Reyher, Matthew B Avison*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

16 Citations (Scopus)
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To characterise putative AmpC hyper-producing 3rd generation cephalosporin-resistant E. coli from dairy farms and their phylogenetic relationships as well as to identify risk factors for their presence; to assess evidence for their zoonotic transmission into the local human population

Proteomics was used to explain differences in antimicrobial susceptibility. Whole genome sequencing allowed phylogenetic analysis. Multilevel, multivariable logistic regression modelling was used to identify risk factors.

Increased use of amoxicillin-clavulanate was associated with an increased risk of finding AmpC hyper-producers on farms. Expansion of cephalosporin resistance in AmpC hyper-producers was seen in farm isolates with marR mutations (conferring cefoperazone resistance) or when AmpC was mutated (conferring 4th generation cephalosporin and cefoperazone resistance). Phylogenetic analysis confirmed the dominance of ST88 amongst farm AmpC hyper-producers but there was no evidence for acquisition of farm isolates by members of the local human population.

Clear evidence was found for recent farm-to-farm transmission of AmpC hyper-producing E. coli and of adaptive mutations to expand resistance. Whilst there was no evidence of isolates entering the local human population, efforts to reduce 3rd generation cephalosporin resistance on dairy farms must address the high prevalence of AmpC hyper-producers. The finding that amoxicillin-clavulanate use was associated with increased risk of finding AmpC hyper-producers is important because this is not currently categorised as a highest-priority critically important antimicrobial and so is not currently targeted for specific usage restrictions in the UK.
Original languageEnglish
Article numberdkaa207
Pages (from-to)2471-2479
Number of pages9
JournalJournal of Antimicrobial Chemotherapy
Issue number9
Early online date15 Jun 2020
Publication statusPublished - 1 Sept 2020


  • mutation
  • cefoperazone
  • geographic area
  • proteomics
  • escherichia coli
  • phylogenetic analysis
  • farming environment
  • whole genome sequencing


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