Ceftazidime-hydrolysing β-lactamase OXA-145 with impaired hydrolysis of penicillins in Pseudomonas aeruginosa. - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Antimicrobial Chemotherapy Année : 2011

Ceftazidime-hydrolysing β-lactamase OXA-145 with impaired hydrolysis of penicillins in Pseudomonas aeruginosa.

Résumé

OBJECTIVES: To describe a novel extended-spectrum oxacillinase, named OXA-145, differing from narrow-spectrum OXA-35 (from the OXA-10 group) by deletion of residue Leu-165. The genetic environment of bla(OXA-145) and the biochemical properties of OXA-145 are reported. We also assessed the impact of the Leu-165 deletion on the hydrolysis spectrum of the ancestor OXA-10. METHODS: Extended-spectrum β-lactamase OXA-145 was identified in the multidrug-resistant clinical Pseudomonas aeruginosa 08-056, and characterized by isoelectric focusing, PCR and DNA sequencing. Antibiotic susceptibility tests were performed by agar dilution. The resistance profiles conferred by cloned bla(OXA-10), bla(OXA-35), bla(OXA-145) and a bla(OXA-10) derivative obtained by site-directed mutagenesis were determined in Escherichia coli. Kinetic parameters of OXA-35 and OXA-145 were established after purification of His-tagged proteins. RESULTS: The sequence of OXA-145, encoded by a class 1 integron-borne gene in strain 08-056, differed from that of narrow-spectrum penicillinase OXA-35 by a single amino acid deletion (Leu-165) located in the highly conserved omega loop. Deletion of Leu-165 from OXA-35 (yielding OXA-145) or OXA-10 (the progenitor of OXA-35) extended the hydrolysis spectrum to third-generation cephalosporins and to monobactams, while reducing that for penicillins. OXA-145 showed biphasic hydrolysis curves for all the substrates tested. Its activity against nitrocefin was 10-fold higher in the presence of sodium hydrogen carbonate. CONCLUSIONS: OXA-145 is a new extended-spectrum β-lactamase from the OXA-10 group. The deletion of Leu-165 is responsible for a shift in the hydrolysis spectrum from penicillins to third-generation cephalosporins, as well as monobactams. The loss of penicillin hydrolysis was due to a non-carboxylated Lys-73.
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hal-00668369 , version 1 (09-02-2012)

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Didier Hocquet, Mélanie Colomb, Barbara Dehecq, Olivier Belmonte, Patrice Courvalin, et al.. Ceftazidime-hydrolysing β-lactamase OXA-145 with impaired hydrolysis of penicillins in Pseudomonas aeruginosa.. Journal of Antimicrobial Chemotherapy, 2011, 66 (8), pp.1745-50. ⟨10.1093/jac/dkr187⟩. ⟨hal-00668369⟩
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