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
2011
Objectives: 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 b-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.
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