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Journal of Clinical Microbiology, Mar 1995, 713-717, Vol 33, No. 3
D Eisen, EG Russell, M Tymms, EJ Roper, ML Grayson and J Turnidge
Multiresistant Klebsiella pneumoniae strains with plasmid-borne
extended-spectrum beta-lactamases (ESBL) are increasingly frequent
nosocomial pathogens. A major outbreak of clinical infections, mainly
involving patients in the Newborn Services Unit with limited spread to
adult patients, occurred at our hospital. This epidemic was investigated by
typing the isolates phenotypically and with random amplified polymorphic
DNA analysis (RAPD) and plasmid analysis. Forty- eight isolates, consisting
of 44 consecutive clinical isolates and 4 selected surveillance isolates,
were studied. A single decamer primer was used for the RAPD, and this was
effective in demonstrating that the majority of isolates (45 of 48) had the
same profile. Three other isolates had different RAPD patterns identifying
them as nonepidemic strains. Plasmids were extracted by alkaline lysis with
Magic-miniprep kits from 10 isolates selected to represent the epidemic and
nonepidemic strains. This method produced small (< 20-kb) plasmids;
larger ESBL-carrying plasmids were not produced, but the small plasmids
nonetheless allowed strain differentiation. Antibiotic susceptibility
patterns alone were not reliable as strain indicators, since some isolates
with the RAPD pattern characteristic of the epidemic strains did not
express ESBL and therefore were susceptible to extended- spectrum
cephalosporins. The investigation showed the predominance of a single
epidemic strain that was transmitted between patients in the Newborn
Services Unit. RAPD was the best of the methods used for detecting strain
differences, and its speed and ability to type a wide variety of species
suggest that it will be an increasingly useful molecular epidemiologic
tool.
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Random amplified polymorphic DNA and plasmid analyses used in investigation of an outbreak of multiresistant Klebsiella pneumoniae
Department of Infectious Diseases and Microbiology, Monash Medical Centre, Clayton, Victoria, Australia.
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