title: Population structure of Escherichia coli causing bacteraemia in the UK and Ireland between 2001 and 2010.
abstract: Escherichia coli is the most common agent of bacteraemia, bacterial gastroenteritis and urinary tract infections (UTIs). Lineages causing UTIs and gastrointestinal disease are well defined, but less is known about those causing bacteraemia. We therefore investigated the population structure of E. coli from bacteraemia in the UK and Ireland between 2001 and 2010.
  
  
  
  E. coli isolates (n = 2166) were submitted to the BSAC Bacteraemia Surveillance Programme from 18 UK and Irish centres from 2001 to 2010. Genotypes were analysed by MLST using the Achtman scheme; MICs, blaCTX-M group and patient demographics were previously determined in the BSAC surveillance.
  
  
  
  Four hundred and forty-eight STs were identified, but five of these, and their associated clonal complexes (CCs), accounted for 58.4% (1264 of 2166) of isolates: CC73 was the most common (20.7%), followed by CC131 (13.9%), CC95 (11.3%), CC69 (6.9%) and CC12 (5.5%). All these, except CC69 (group D), belong to phylogenetic group B2. CC131 isolates were much more often MDR than other STs were: they rose from 2.9% of isolates in 2001 to 20.5%-20.7% in 2007-08 and then declined to 14.3% in 2010. Resistance rates to cephalosporins, aminoglycosides and fluoroquinolones remained below 10% in other major CCs throughout.
  
  
  
  The five most prevalent bacteraemia STs have all been associated previously with UTIs. They dominated in all years, but their proportions fluctuated, most notably for ST131, a globally disseminated high-risk clone that is often MDR.
authors.affiliation: National Infection Service, Public Health England, London NW9 5EQ, UK michaela.day@phe.gov.uk.
authors.forename: M J
authors.initials: MJ
authors.lastname: Day
authors.affiliation: National Infection Service, Public Health England, London NW9 5EQ, UK.
authors.forename: M
authors.initials: M
authors.lastname: Doumith
authors.affiliation: National Infection Service, Public Health England, London NW9 5EQ, UK.
authors.forename: J
authors.initials: J
authors.lastname: Abernethy
authors.affiliation: National Infection Service, Public Health England, London NW9 5EQ, UK.
authors.forename: R
authors.initials: R
authors.lastname: Hope
authors.affiliation: Department of Medical Microbiology, Southmead Hospital, Bristol BS10 5NB, UK.
authors.forename: R
authors.initials: R
authors.lastname: Reynolds
authors.affiliation: Norwich Medical School, University of East Anglia, Norwich NR4 7TJ, UK.
authors.forename: J
authors.initials: J
authors.lastname: Wain
authors.affiliation: National Infection Service, Public Health England, London NW9 5EQ, UK Norwich Medical School, University of East Anglia, Norwich NR4 7TJ, UK.
authors.forename: D M
authors.initials: DM
authors.lastname: Livermore
authors.affiliation: National Infection Service, Public Health England, London NW9 5EQ, UK.
authors.forename: N
authors.initials: N
authors.lastname: Woodford
mesh_terms: D000293:Adolescent; D016470:Bacteremia / Q000453:epidemiology / Q000382:microbiology*; D002648:Child; D002675:Child, Preschool; D004926:Escherichia coli / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology*; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007494:Ireland / Q000453:epidemiology; D008297:Male; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D058885:Multilocus Sequence Typing; D015995:Prevalence; D006113:United Kingdom / Q000453:epidemiology; D055815:Young Adult; D001618:beta-Lactamases / Q000032:analysis
chemical_list: D001618:beta-Lactamases