title: Prevalence and mechanisms of cephalosporin resistance in Enterobacteriaceae in London and South-East England.
abstract: OBJECTIVE
  To investigate the molecular epidemiology of Enterobacteriaceae producing extended-spectrum beta-lactamases (ESBLs) in London and South-East England.
  
  
  METHODS
  A prospective study involving 16 hospital microbiology laboratories in London and South-East England was undertaken over a 12 week period. Each laboratory submitted up to 100 consecutive cephalosporin-resistant Enterobacteriaceae isolates judged clinically significant by microbiology staff. Centralized testing was undertaken to confirm organism identification and cephalosporin resistance and to analyse resistance mechanisms.
  
  
  RESULTS
  The predominant mechanism of cephalosporin resistance in isolates from both hospital and community settings was the production of CTX-M-type ESBLs, with CTX-M-producing Escherichia coli as the most numerous resistant organism overall. Other major mechanisms of cephalosporin resistance included production of non-CTX-M ESBLs and AmpC beta-lactamases. Most ESBL (both CTX-M and non-CTX-M) producers were multiply resistant to non-beta-lactam antibiotics, including trimethoprim, ciprofloxacin and gentamicin.
  
  
  CONCLUSIONS
  CTX-M enzymes, which were unrecorded in the UK prior to 2000, have become the major mechanism of cephalosporin resistance in Enterobacteriaceae in South-East England. E. coli has overtaken Klebsiella and Enterobacter spp. to become the major host for ESBLs. Due to the multiple antibiotic resistance exhibited by many ESBL-producers, these changes have major implications for antimicrobial therapy.
authors.affiliation: Healthcare-Associated Infection and Antimicrobial Resistance Department, Health Protection Agency Centre for Infections 61 Colindale Avenue, London NW9 5EQ, UK. nicola.potz@HPA.org.uk
authors.forename: Nicola A C
authors.initials: NA
authors.lastname: Potz
authors.forename: Russell
authors.initials: R
authors.lastname: Hope
authors.forename: Marina
authors.initials: M
authors.lastname: Warner
authors.forename: Alan P
authors.initials: AP
authors.lastname: Johnson
authors.forename: David M
authors.initials: DM
authors.lastname: Livermore
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis; D018550:Cephalosporin Resistance; D002511:Cephalosporins / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D004269:DNA, Bacterial / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D004739:England; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D005260:Female; D006801:Humans; D007223:Infant; D008131:London; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D001618:beta-Lactamases / Q000096:biosynthesis
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D002511:Cephalosporins; D004269:DNA, Bacterial; D001618:beta-Lactamases