title: Regional survey of CTX-M-type extended-spectrum β-lactamases among Enterobacteriaceae reveals marked heterogeneity in the distribution of the ST131 clone.
abstract: OBJECTIVE
  To establish the prevalence and diversity of clinically significant extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae harbouring bla(CTX-M) in the West Midlands region of the UK.
  
  
  METHODS
  During a 2 month period, 370 consecutive, non-duplicate isolates were collected from 13 laboratories. Isolates were screened for the presence of bla(CTX-M) by multiplex PCR and genotyped using denaturing HPLC (DHPLC). Clonal relationships were studied by PFGE and O25b-ST131 Escherichia coli were identified by PCR.
  
  
  RESULTS
  Two hundred and ninety-four out of 345 ESBL-producing isolates (85.2%) carried bla(CTX-M). CTX-M group 1 enzymes were expressed in 284 (96.6%) isolates, with the other 10 carrying group 9, 2 and 25/26 genes. All group 1 isolates had bla(CTX-M-15) DHPLC profiles. The bla(CTX-M) E. coli were split into 23 PFGE clusters. The largest cluster (RE1) was indistinguishable from the previously described strain A and all but one harboured bla(CTX-M-15.) A total of 66% of E. coli were O25b-ST131 positive.
  
  
  CONCLUSIONS
  The CTX-M-15-producing RE1 clone (strain A) is the predominant clone in the West Midlands. This clone has spread throughout the region since its emergence in an outbreak 3 years earlier. Most, but not all, RE1 isolates belong to the O25b-ST131 lineage, providing further evidence that this lineage plays a pivotal role in the clonal dispersal of CTX-M-15-producing Enterobacteriaceae. Strain A was found to be considerably more heterogeneous than when first described and has acquired greater resistance to gentamicin. Approximately one-third of CTX-M producers represented a wide variety of unrelated strains. The study shows the rapid spread and diversification of CTX-M-producing Enterobacteriaceae over a 3 year period.
authors.affiliation: Health Protection Agency, West Midlands Public Health Laboratory, Heart of England NHS Foundation Trust, Bordesley Green East, Birmingham B9 5SS, UK. l.mccrae@bham.ac.uk
authors.forename: Li
authors.initials: L
authors.lastname: Xu
authors.forename: Sahida
authors.initials: S
authors.lastname: Shabir
authors.forename: Thomas
authors.initials: T
authors.lastname: Bodah
authors.forename: Claire
authors.initials: C
authors.lastname: McMurray
authors.forename: Katie
authors.initials: K
authors.lastname: Hardy
authors.forename: Peter
authors.initials: P
authors.lastname: Hawkey
authors.forename: Kathryn
authors.initials: K
authors.lastname: Nye
mesh_terms: D015373:Bacterial Typing Techniques; D004269:DNA, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004591:Electrophoresis, Polyacrylamide Gel; D004755:Enterobacteriaceae / Q000145:classification* / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000453:epidemiology* / Q000382:microbiology; D006801:Humans; D017720:Molecular Epidemiology; D058889:Molecular Typing; D009691:Nucleic Acid Denaturation; D016133:Polymerase Chain Reaction; D015995:Prevalence; D006113:United Kingdom / Q000453:epidemiology; D001618:beta-Lactamases / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D001618:beta-Lactamases