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  • Characterization of the inhibitor-resistant SHV β-lactamase SHV-107 in a clinical Klebsiella pneumoniae strain co-producing GES-7 enzyme
    Publication . Manageiro, Vera; Ferreira, Eugénia; Cougnoux, Antony; Albuquerque, Luís; Caniça, Manuela; Bonnet, Richard
    The clinical Klebsiella pneumoniae INSRA6884 strain exhibited nonsusceptibility to all penicillins tested (MICs of 64 to>2,048 g/ml). The MICs of penicillins were weakly reduced by clavulanate (from 2,048 to 512 g/ml), and tazobactam restored piperacillin susceptibility. Molecular characterization identified the genes blaGES-7 and a new -lactamase gene, blaSHV-107, which encoded an enzyme that differed from SHV-1 by the amino acid substitutions Leu35Gln and Thr235Ala. The SHV-107-producing Escherichia coli strain exhibited only a -lactam resistance phenotype with respect to amoxicillin, ticarcillin, and amoxicillinclavulanate combination. The kinetic parameters of the purified SHV-107 enzyme revealed a high affinity for penicillins. However, catalytic efficiency for these antibiotics was lower for SHV-107 than for SHV-1. No hydrolysis was detected against oxyimino- -lactams. The 50% inhibitory concentration (IC50) for clavulanic acid was 9-fold higher for SHV-107 than for SHV-1, but the inhibitory effects of tazobactam were unchanged. Molecular dynamics simulation suggested that the Thr235Ala substitution affects the accommodation of clavulanate in the binding site and therefore its inhibitory activity.
    2012Artigo científico Acesso aberto Ver mais