Isolation of fluoroquinolone-resistant O25b:H4-ST131 Escherichia coli with CTX-M-14 extended-spectrum β-lactamase from UK river water

Hiran Dhanji, Niamh M. Murphy, Christine Akhigbe, Michel Doumith, Russell Hope, David M. Livermore, Neil Woodford

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Objectives We analysed water sampled from the River Thames in London for Escherichia coli resistant to oxyimino-cephalosporins and/or fluoroquinolones, particularly seeking isolates with CTX-M extended-spectrum ß-lactamases (ESBLs) and members of the clinically important O25b:H4-ST131 lineage. Methods River water was collected from three urban sites on the River Thames by the City of London Port Health Authority on two occasions 1 week apart. Coliforms and E. coli were identified by the Quanti-Tray™ method. Disc susceptibility tests were performed and MICs were determined for E. coli isolates resistant to either ciprofloxacin or cefpodoxime and genetic relatedness was determined by PFGE and real-time PCR. PCR was used for phylogenetic and plasmid typing, to detect antibiotic resistance genes and to detect ISEcp1 upstream of blaCTX-M genes. blaCTX-M alleles were identified by sequencing. Results The mean E. coli count, as the most probable number, from the first river samples, taken on a falling tide on 23 March 2010, was 4.7?×?104/100 mL and 30 ciprofloxacin-resistant colonies were isolated. Twenty of the 30 colonies belonged to clone ST131; 10 of these had blaCTX-M-14 whereas the remaining 10 lacked ESBLs. The ST131 isolates represented two different PFGE types. No ciprofloxacin- or cefpodoxime-resistant E. coli were isolated from the second river sample taken at low tide. CTX-M-15, the most common ESBL in clinical E. coli, was not detected in the river samples. Conclusions Water from the River Thames in West London is contaminated, perhaps transiently, with antibiotic-resistant E. coli belonging to the clinically important O25b:H4-ST131 lineage.
Original languageEnglish
Pages (from-to)512-516
Number of pages5
JournalJournal of Antimicrobial Chemotherapy
Issue number3
Publication statusPublished - Mar 2011


  • Anti-Bacterial Agents
  • Bacterial Typing Techniques
  • Drug Resistance, Bacterial
  • Electrophoresis, Gel, Pulsed-Field
  • Escherichia coli
  • Fluoroquinolones
  • Humans
  • London
  • Microbial Sensitivity Tests
  • Molecular Typing
  • Plasmids
  • Polymerase Chain Reaction
  • Rivers
  • beta-Lactamases
  • beta-Lactams

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