Community and hospital spread of Escherichia coli producing CTX-M extended-spectrum ²-lactamases in the UK

• Published in: Journal of antimicrobial chemotherapy 2004-10, Vol.54 (4), p.735
• Main Authors: Woodford, N, Ward, M E, Kaufmann, M E, Turton, J, Fagan, E J, James, D, Johnson, A P, Pike, R, Warner, M, Cheasty, T, Pearson, A, Harry, S, Leach, J B, Loughrey, A, Lowes, J A, Warren, R E, Livermore, D M
• Format: Article
• Language: English
• ISSN: 0305-7453; 1460-2091

Objectives: During 2003, the Health Protection Agency's Antibiotic Resistance Monitoring and Reference Laboratory began to receive isolates of Escherichia coli for confirmation of extended-spectrum ²-lactamase production with a phenotype implying a CTX-M-type ²-lactamase, i.e. MICs of cefotaxime e8-fold higher than MICs of ceftazidime. Many were referred as being from community patients. We examined 291 CTX-M-producing isolates from the UK and investigated the genetic basis of their phenotype. Methods: PCR was used to detect alleles encoding CTX-M enzymes and to assign these to their bla CTX-M phylogenetic groups. Selected alleles were sequenced. Producers were compared by analysis of banding patterns generated by pulsed-field gel electrophoresis of XbaI-digested genomic DNA. MICs were determined by an agar dilution method or by Etest. Results: Of 291 CTX-M-producing E. coli isolates studied from 42 UK centres, 70 (24%) were reportedly from community patients, many of whom had only limited recent hospital contact. Community isolates were referred by 12 centres. Two hundred and seventy-nine (95.9%) producers contained genes encoding group 1 CTX-M enzymes and 12 contained bla CTX-M-9 -like alleles. An epidemic CTX-M-15-producing strain was identified, with 110 community and inpatient isolates referred from six centres. Representatives of four other major strains also produced CTX-M-15, as did several sporadic isolates examined. Most producers were multi-resistant to fluoroquinolones, trimethoprim, tetracycline and aminoglycosides as well as to non-carbapenem ²-lactams. Conclusions: CTX-M-producing E. coli are a rapidly developing problem in the UK, with CTX-M-15 particularly common. The diversity of producers and geographical scatter of referring laboratories indicates wide dissemination of bla CTX-M genes. Because of the public health implications, including for the treatment of community-acquired urinary tract infections, the spread of these strains--and CTX-M-15 ²-lactamase in particular--merits close monitoring.