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. 2007 May;45(5):1478-82.
doi: 10.1128/JCM.02470-06. Epub 2007 Mar 7.

Prevalence and significance of a negative extended-spectrum beta-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

Jan M Bell  1 , Mohsen Chitsaz, John D Turnidge, Mary Barton, Luke J Walters, Ronald N Jones
Affiliations

Prevalence and significance of a negative extended-spectrum beta-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

Jan M Bell et al. J Clin Microbiol. 2007 May.

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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Figures

FIG. 1.
FIG. 1.
Breakdown of E. coli and K. pneumoniae isolates by results of ESBL screening and confirmation tests, and MICs to screening agents. Abbreviations: Ctz, ceftazidime; Ctr, ceftriaxone; and Azt, aztreonam.
FIG. 2.
FIG. 2.
Prevalence by country of E. coli and K. pneumoniae with a positive ESBL screen that confirmed and did not confirm. AUS, Australia; HKC, Hong Kong; CHI, China; KOR, Korea; PHI, the Philippines; SIN, Singapore; SAF, South Africa; TWN, Taiwan. Numbers above the bars represent the total number of strains tested in each country.
See this image and copyright information in PMC

References

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    1. Bell, J. M., J. D. Turnidge, A. C. Gales, M. A. Pfaller, R. N. Jones, and the SENTRY APAC group. 2002. Prevalence of extended-spectrum β-lactamase (ESBL)-producing clinical isolates in the Asia-pacific region and South Africa: regional results from SENTRY Antimicrobial Surveillance Program (1998-99). Diagn. Microbiol. Infect. Dis. 42:193-198. - PubMed
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