JCM Figure table search 04
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Moland, E. S.
Right arrow Articles by Thomson, K. S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Moland, E. S.
Right arrow Articles by Thomson, K. S.

 Previous Article  |  Next Article 

Journal of Clinical Microbiology, September 1998, p. 2575-2579, Vol. 36, No. 9
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

Can Results Obtained with Commercially Available MicroScan Microdilution Panels Serve as an Indicator of beta -Lactamase Production among Escherichia coli and Klebsiella Isolates with Hidden Resistance to ExpandedSpectrum Cephalosporins and Aztreonam?

Ellen Smith Moland,* Christine C. Sanders, and Kenneth S. Thomson

Center for Research in Anti-Infectives and Biotechnology, Department of Medical Microbiology and Immunology, Creighton University, Omaha, Nebraska 68178

Received 30 March 1998/Returned for modification 15 May 1998/Accepted 14 June 1998

Among clinical isolates of Escherichia coli, Klebsiella pneumoniae, and Klebsiella oxytoca, there is an ever-increasing prevalence of beta -lactamases that may confer resistance to newer beta -lactam antibiotics that is not detectable by conventional procedures. Therefore, 75 isolates of these species producing well-characterized beta -lactamases were studied using two MicroScan conventional microdilution panels, Gram Negative Urine MIC 7 (NU7) and Gram Negative MIC Plus 2 (N+2), to determine if results could be utilized to provide an accurate indication of beta -lactamase production in the absence of frank resistance to expanded-spectrum cephalosporins and aztreonam. The enzymes studied included Bush groups 1 (AmpC), 2b (TEM-1, TEM-2, and SHV-1), 2be (extended spectrum beta -lactamases [ESBLs] and K1), and 2br, alone and in various combinations. In tests with E. coli and K. pneumoniae and the NU7 panel, cefpodoxime MICs of >= 2 µg/ml were obtained only for isolates producing ESBLs or AmpC beta -lactamases. Cefoxitin MICs of >16 µg/ml were obtained for all strains producing AmpC beta -lactamase and only 1 of 33 strains producing ESBLs. For the N+2 panel, ceftazidime MICs of >= 4 µg/ml correctly identified 90% of ESBL producers and 100% of AmpC producers among isolates of E. coli and K. pneumoniae. Cefotetan MICs of >=  8 µg/ml were obtained for seven of eight producers of AmpC beta -lactamase and no ESBL producers. For tests performed with either panel and isolates of K. oxytoca, MICs of ceftazidime, cefotaxime, and ceftizoxime were elevated for strains producing ESBLs, while ceftriaxone and aztreonam MICs separated low-level K1 from high-level K1 producers within this species. These results suggest that microdilution panels can be used by clinical laboratories as an indicator of certain beta -lactamases that may produce hidden but clinically significant resistance among isolates of E. coli, K. pneumoniae, and K. oxytoca. Although it may not always be possible to differentiate between strains that produce ESBLs and those that produce AmpC, this differentiation is not critical since therapeutic options for patients infected with such organisms are similarly limited.

* Corresponding author. Mailing address: Center for Research in Anti-Infectives and Biotechnology, Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE 68178. Phone: (402) 280-1881. Fax: (402) 280-1225. E-mail: esmoland{at}creighton.edu.

Journal of Clinical Microbiology, September 1998, p. 2575-2579, Vol. 36, No. 9
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
Antimicrob. Agents Chemother. Clin. Microbiol. Rev.
Clin. Vaccine Immunol. ALL ASM JOURNALS

Copyright © 1998 by the American Society for Microbiology. All rights reserved.