Use of Microdilution Panels with and without β-Lactamase Inhibitors as a Phenotypic Test for β-Lactamase Production among Escherichia coli , Klebsiella spp., Enterobacter spp., Citrobacter freundii , and Serratia marcescens
- 1 June 1999
- journal article
- research article
- Published by American Society for Microbiology in Antimicrobial Agents and Chemotherapy
- Vol. 43 (6), 1393-1400
- https://doi.org/10.1128/aac.43.6.1393
Abstract
Over the past decade, a number of new β-lactamases have appeared in clinical isolates of Enterobacteriaceaethat, unlike their predecessors, do not confer β-lactam resistance that is readily detected in routine antibiotic susceptibility tests. Because optimal methodologies are needed to detect these important new β-lactamases, a study was designed to evaluate the ability of a panel of various β-lactam antibiotics tested alone and in combination with β-lactamase inhibitors to discriminate between the production of extended-spectrum β-lactamases, AmpC β-lactamases, high levels of K1 β-lactamase, and other β-lactamases in 141 isolates of Escherichia coli,Klebsiella pneumoniae, Klebsiella oxytoca,Enterobacter cloacae, Enterobacter aerogenes,Citrobacter freundii, and Serratia marcescens possessing well-characterized β-lactamases. The microdilution panels studied contained aztreonam, cefpodoxime, ceftazidime, cefotaxime, and ceftriaxone, with and without 1, 2, and 4 μg of clavulanate per ml or 8 μg of sulbactam per ml and cefoxitin and cefotetan with and without 8 μg of sulbactam per ml. The results indicated that a minimum panel of five tests would provide maximum separation of extended-spectrum β-lactamase high AmpC, high K1, and other β-lactamase production in Enterobacteriaceae. These included cefpodoxime, cefpodoxime plus 4 μg of clavulanate per ml, ceftazidime, ceftriaxone, and ceftriaxone plus 8 μg of sulbactam per ml. Ceftriaxone plus 2 μg of clavulanate per ml could be substituted for cefpodoxime plus 4 μg of clavulanate per ml without altering the accuracy of the tests. This study indicated that tests with key β-lactam drugs, alone and in combination with β-lactamase inhibitors, could provide a convenient approach to the detection of a variety of β-lactamases in members of the family Enterobacteriaceae.This publication has 67 references indexed in Scilit:
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