title: Impact of a clonal outbreak of extended-spectrum β-lactamase-producing Klebsiella pneumoniae in the development and evolution of bloodstream infections by K. pneumoniae and Escherichia coli: an 11 year experience in Oxfordshire, UK.
abstract: OBJECTIVE
  The objectives of this study were: (i) to describe an outbreak of multidrug-resistant Klebsiella pneumoniae in our population; (ii) to identify the potential source of this outbreak by examining antibiotic resistance trends in urocultures; (iii) to evaluate the contribution of this outbreak to resistance patterns over time in the two commonest Gram-negative blood culture isolates, namely K. pneumoniae and Escherichia coli; and (iv) to assess risk factors for multidrug resistance and the impact of this resistance on mortality and length of stay.
  
  
  METHODS
  We searched Microbiology and Patient Administration Service databases retrospectively and describe resistance trends in E. coli and K. pneumoniae bloodstream infections (BSIs) in Oxfordshire, UK, over an 11 year period.
  
  
  RESULTS
  An outbreak of a multidrug-resistant, CTX-M-15 extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae clone was identified and shown by multilocus sequence typing to belong to a novel sequence type designated ST490. This was associated with a sporadic change in resistance rates in K. pneumoniae BSIs with rates of multidrug resistance (defined as resistance to three or more antibiotic classes) reaching 40%. A case-control study showed prior antibiotic exposure as a risk factor for infection with this organism. During the same time period, rates of ESBL-producing Klebsiella spp. isolated from urocultures increased from 0.5% to almost 6%. By contrast, the rate of multidrug resistance in E. coli rose more steadily from 0% in 2000 to 10% in 2010.
  
  
  CONCLUSIONS
  Changes in resistance rates may be associated with outbreaks of resistant clones in K. pneumoniae. Changing resistance patterns may affect important health economic issues such as length of stay.
authors.affiliation: Brighton and Sussex Medical School, Falmer, UK. d.webster@bsms.ac.uk
authors.forename: D P
authors.initials: DP
authors.lastname: Webster
authors.forename: B C
authors.initials: BC
authors.lastname: Young
authors.forename: R
authors.initials: R
authors.lastname: Morton
authors.forename: D
authors.initials: D
authors.lastname: Collyer
authors.forename: B
authors.initials: B
authors.lastname: Batchelor
authors.forename: J F
authors.initials: JF
authors.lastname: Turton
authors.forename: S
authors.initials: S
authors.lastname: Maharjan
authors.forename: D M
authors.initials: DM
authors.lastname: Livermore
authors.forename: P
authors.initials: P
authors.lastname: Bejon
authors.forename: B D
authors.initials: BD
authors.lastname: Cookson
authors.forename: I C J W
authors.initials: IC
authors.lastname: Bowler
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D003422:Critical Care; D003428:Cross Infection / Q000188:drug therapy / Q000382:microbiology / Q000401:mortality; D004196:Disease Outbreaks; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000187:drug effects; D004927:Escherichia coli Infections / Q000097:blood* / Q000382:microbiology* / Q000652:urine; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007710:Klebsiella Infections / Q000097:blood* / Q000382:microbiology* / Q000652:urine; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000201:enzymology*; D007902:Length of Stay; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D006113:United Kingdom / Q000453:epidemiology; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*
chemical_list: D001618:beta-Lactamases