Origin and impact of plasmid-mediated extended-spectrum beta-lactamases |
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Authors: | A. Philippon G. Arlet P. H. Lagrange |
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Affiliation: | 1.Laboratoire de Bactériologie-Virologie,H?pital Saint-Louis,Paris Cedex 10,France |
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Abstract: | Resistance to oxyimino cephalosporins was originally highlighted by the emergence of plasmid-encoded extended-spectrum β-lactamases deriving by mutation from TEM-1, TEM-2 and SHV type enzymes (class A). The broader spectrum of resistance produced by these enzymes is related to more amino acid substitutions, but susceptibility to seven alpha-methoxyimino cephalosporins and carbapenems was preserved until recently. Clavulanate-sensitive extended-spectrum β-lactamases are distributed worldwide, mainly amongKlebsiella pneumoniae isolates. Novel clavulanate-sensitive extended-spectrum β-lactamases deriving from other class A enzymes (e.g. MEN-1 from βlaOXY, OXA-11 inPseudomonas aeruginosa from PSE-2) have been reported. Recently, clavulanate-resistant extended-spectrum β-lactamases (class C) were encountered amongst single isolates, mostlyKlebsiella pneumoniae. These cephalosporinases or cefamycinases (usually chromosomally mediated) have expanded the spectrum of plasmid-encoded resistance to include seven alpha-methoxyimino cephalosporins. Thus far, only two isolates (1Pseudomonas aeruginosa, 1Bacteroides fragilis), both recovered in Japan, with plasmid-mediated resistance to carbapenems have been found. |
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