Genetic and functional analysis of the chromosome-encoded carbapenem-hydrolyzing oxacillinase OXA-40 of Acinetobacter baumannii - PubMed (original) (raw)

Genetic and functional analysis of the chromosome-encoded carbapenem-hydrolyzing oxacillinase OXA-40 of Acinetobacter baumannii

Claire Héritier et al. Antimicrob Agents Chemother. 2003 Jan.

Abstract

Clinical isolate Acinetobacter baumannii CLA-1 was resistant to a series of antibiotic molecules, including carbapenems. Cloning and expression of the beta-lactamase gene content of this isolate in Escherichia coli DH10B identified a chromosome-encoded oxacillinase, OXA-40, that differed by one or two amino acid changes from OXA-24, -25, and -26 and an AmpC-type cephalosporinase. The OXA-40 beta-lactamase had a mainly narrow-spectrum hydrolytic profile, but it included ceftazidime and imipenem. Its activity was resistant to inhibition by clavulanic acid, tazobactam, sulbactam, and, like most of the other carbapenem-hydrolyzing oxacillinases, NaCl. OXA-40 had an FGN triad replacing a YGN motif at class D beta-lactamase (DBL) positions 144 to 146. Site-directed DNA mutagenesis leading to a Phe-to-Tyr change at DBL position 144 in OXA-40 gave a mutant enzyme with increased hydrolytic activity against most beta-lactams, including imipenem. Conversely, with a gene encoding the narrow-spectrum oxacillinase OXA-1 as the template, a nucleotide substitution leading to a Tyr-to-Phe change in the YGN motif of OXA-1 gave a mutant enzyme with decreased hydrolytic activity without an increase in carbapenem-hydrolyzing activity. Thus, the Phe residue in the FGN motif was not associated with carbapenem-hydrolyzing activity by itself but instead was associated with weak overall hydrolytic activity. Finally, this Phe residue in OXA-40 explained resistance to inhibition by NaCl whereas a Tyr residue in motif YGN was related to susceptibility to NaCl.

PubMed Disclaimer

Figures

FIG. 1.

FIG. 1.

Comparison of the amino acid sequence of OXA-40 to those of the most closely related oxacillinases, OXA-24, -25, and -26 (3, 10). Dashes indicate identical amino acids. The numbering is in accordance with the DBL numbering system (14). The motifs usually conserved among DBLs are shaded.

Similar articles

Cited by

References

    1. Afzal-Shah, M., and D. M. Livermore. 1998. Worldwide emergence of carbapenem-resistant Acinetobacter spp. J. Antimicrob. Chemother. 41:576-577. - PubMed
    1. Afzal-Shah, M., H. E. Villar, and D. M. Livermore. 1999. Biochemical characteristics of a carbapenemase from an Acinetobacter baumannii isolate collected in Buenos Aires, Argentina. J. Antimicrob. Chemother. 43:127-131. - PubMed
    1. Afzal-Shah, M., N. Woodford, and D. M. Livermore. 2001. Characterization of OXA-25, OXA-26, and OXA-27, molecular class D β-lactamases associated with carbapenem resistance in clinical isolates of Acinetobacter baumannii. Antimicrob. Agents Chemother. 45:583-588. - PMC - PubMed
    1. Aubert, D., L. Poirel, J. Chevalier, S. Léotard, J.-M. Pagès, and P. Nordmann. 2001. Oxacillinase-mediated resistance to cefepime and susceptibility to ceftazidime in Pseudomonas aeruginosa. Antimicrob. Agents Chemother. 45:1615-1620. - PMC - PubMed
    1. Avidor, B., Y. Kletter, S. Abulafia, Y. Golan, M. Ephros, and M. Giladi. 1997. Molecular diagnosis of cat scratch disease: a two step approach. J. Clin. Microbiol. 35:1924-1930. - PMC - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources