A simple disc diffusion method for detecting AmpC and extended-spectrum beta-lactamases in clinical isolates of Enterobacteriaceae

Derbyshire, Helen, Kay, Gemma, Evans, Katie, Vaughan, Carmel, Kavuri, Umadevi and Winstanley, Trevor (2009) A simple disc diffusion method for detecting AmpC and extended-spectrum beta-lactamases in clinical isolates of Enterobacteriaceae. Journal of Antimicrobial Chemotherapy, 63 (3). pp. 497-501. ISSN 0305-7453

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Abstract

BACKGROUND: We sought to determine whether extended-spectrum beta-lactamases (ESBLs) and AmpC beta-lactamases (derepressed and inducible), alone and in combination, could be detected in unidentified members of the Enterobacteriaceae using a simple, overnight disc diffusion test. METHODS: The genetic basis of antibiotic resistance in cephalosporin-resistant wild-type (n = 140) and culture collection (n = 140) isolates of Enterobacteriaceae was determined using PCR. A scheme for detecting these resistance mechanisms phenotypically was devised using five antibiotic discs: cefpodoxime +/- clavulanate; cefepime +/- clavulanate and cefoxitin. RESULTS AND CONCLUSIONS: AmpC beta-lactamases (derepressed and inducible) and ESBLs, alone and in combination, could reliably be detected using a disc diffusion method. ESBLs alone could be detected on the basis of a difference of >5 mm between cefpodoxime/clavulanate and cefpodoxime (10 microg) discs. ESBLs, in the presence of AmpC beta-lactamases, could be detected using a difference of >5 mm between cefepime/clavulanate and cefepime (30 microg) discs. AmpC beta-lactamases could be detected using a difference of >14 mm between cefepime/clavulanate and cefpodoxime/clavulanate discs. Inducible AmpC beta-lactamases could be discerned by observing the blunting of the cefpodoxime or cefpodoxime/clavulanate zones in proximity to cefoxitin (30 microg) discs.

Item Type: Article
Uncontrolled Keywords: anti-bacterial agents,bacteriological techniques,dna, bacterial,enterobacteriaceae,enterobacteriaceae infections,humans,microbial sensitivity tests,polymerase chain reaction,beta-lactam resistance,beta-lactamases,beta-lactams
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
Depositing User: Pure Connector
Date Deposited: 24 Sep 2016 00:47
Last Modified: 22 Apr 2020 01:43
URI: https://ueaeprints.uea.ac.uk/id/eprint/60220
DOI: 10.1093/jac/dkn535

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