CTX-M and AmpC genes in human isolates of Escherichia coli, their genetic environment and their host plasmids were examined. Isolates (n = 103) were selected based on resistance (minimum inhibitory concentration (MIC) ≥ 1 μg/mL) to ceftriaxone and cefotaxime. Polymerase chain reaction (PCR) and sequencing identified 29 isolates containing blaCTX-M-15, 1 each of blaCTX-M-2 (a strain originating from Israel) and blaCTX-M-40, 20 isolates containing blaCMY-7, 4 blaCMY-2 and 1 blaCMY-21. This is the first study of plasmid-mediated AmpC genes in E. coli in the UK. Eleven cefoxitin-resistant, AmpC PCR-negative isolates had ampC promoter region mutations. All blaCTX-M-15 and 24 of 25 blaCMY genes were associated with an ISEcp1-like element. The blaCTX-M-2 was located in an orf513-bearing class 1 integron. Plasmid restriction digests suggest transfer of genes between different plasmid backbones.
Bibliographical noteFunding Information:
This study was funded by the Department of Food, Environment and Rural Affairs (Defra), United Kingdom (project VM02136). We would like to thank Tom Cheasty, Laboratory of Enteric Pathogens, Health Protection Agency Centre for Infections (HPA CfI), for providing the strains; and Edi Karisik, Antibiotic Resistance Monitoring and Reference Laboratory (ARMRL), HPA CfI, for help with the transformation experiments. We also thank Neil Woodford, ARMRL, HPA CfI, for contributive discussion.
- Antimicrobial resistance
- Escherichia coli
- ampC promoter