Variable susceptibility to piperacillin/tazobactam amongst Klebsiella spp. with extended-spectrum beta-lactamases

Babini, Gioia S, Yuan, Meifang, Hall, Lucinda M C and Livermore, David M ORCID: (2003) Variable susceptibility to piperacillin/tazobactam amongst Klebsiella spp. with extended-spectrum beta-lactamases. Journal of Antimicrobial Chemotherapy, 51 (3). pp. 605-612. ISSN 0305-7453

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MICs of piperacillin/tazobactam are conventionally determined by varying the concentration of piperacillin in the presence of a fixed 4 mg/L tazobactam. When tested in this way, the MIC distribution for Klebsiella isolates with extended-spectrum beta-lactamases (ESBLs) is strongly bimodal, such that many producers are inhibited at 16 + 4 mg/L whilst others require MICs of > or =512 + 4 mg/L. When, however, piperacillin/tazobactam was tested as a fixed 8:1 ratio, the MIC distribution became unimodal. If clavulanate 4 mg/L was combined with piperacillin, a unimodal MIC distribution was seen for ESBL-producing Klebsiella spp. but a bimodal distribution arose if the clavulanate concentration was reduced to 0.25 mg/L. These data for alternative combinations suggested that the bimodal MIC distribution seen for piperacillin + tazobactam 4 mg/L was a titration effect, not a reflection of some ESBLs being resistant to tazobactam. Even within single strains, as defined by serotype and DNA fingerprints, there was considerable variation in susceptibility to piperacillin + tazobactam 4 mg/L, with some representatives highly susceptible and others highly resistant. Some of the more resistant representatives produced more of their ESBL, or had a greater number of beta-lactamase types, but these associations were not universal. Elevated resistance to piperacillin + tazobactam was not associated with porin change in any ESBL producer examined, but has been found by others.

Item Type: Article
Uncontrolled Keywords: bacterial outer membrane proteins,drug resistance, multiple, bacterial,humans,klebsiella,microbial sensitivity tests,penicillanic acid,piperacillin,beta-lactamases
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
Depositing User: Pure Connector
Date Deposited: 24 Jan 2014 12:36
Last Modified: 24 Oct 2022 05:47

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