Prevalence and significance of a negative extended-spectrum β-lactamase (ESBL) confirmation test result after a positive ESBL screening test result for isolates of Escherichia coli and Klebsiella pneumoniae: Results from the SENTRY Asia-Pacific Surveillance Program
Date
2007
Authors
Bell, J.
Chitsaz, M.
Turnidge, J.
Barton, M.
Walters, L.
Jones, R.
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Journal article
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Journal of Clinical Microbiology, 2007; 45(5):1478-1482
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Jan M. Bell, Mohsen Chitsaz, John D. Turnidge, Mary Barton, Luke J. Walters, and Ronald N. Jones
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Abstract
A negative extended-spectrum beta-lactamase (ESBL) confirmation test result obtained after a positive ESBL screening test result using Clinical and Laboratory Standards Institute methods has been a common occurrence among isolates of Escherichia coli and Klebsiella pneumoniae in the SENTRY Antimicrobial Surveillance Program in the Asia-Pacific region. Among isolates collected between 1998 and 2004 this screen-positive, nonconfirmed profile (failed to show clavulanate synergy) was observed in 8.9% of 4,515 E. coli isolates and 20.3% of 2,303 K. pneumoniae isolates. We then selected 52 E. coli isolates and 68 K. pneumoniae isolates with a negative ESBL confirmation test, as well as comparable number of isolates with confirmed ESBL-positive tests, and examined them for the presence of TEM, SHV, plasmid-borne ampC, and CTX-M genes. We found that 62% of nonconfirming E. coli isolates and 75% of nonconfirming K. pneumoniae harbored a plasmid-borne AmpC enzyme of the CIT or DHA type. The majority of nonconfirming E. coli and K. pneumoniae from the Asia-Pacific region harbor important beta-lactamases, and a positive screening test alone should be sufficient grounds to report resistance to extended-spectrum cephalosporins in this region.
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Copyright © 2007, American Society for Microbiology. All Rights Reserved.