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Antimicrobial Agents and Chemotherapy, February 2008, p. 551-556, Vol. 52, No. 2
0066-4804/08/$08.00+0     doi:10.1128/AAC.01145-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Genetic and Biochemical Characterization of CAD-1, a Chromosomally Encoded New Class A Penicillinase from Carnobacterium divergens{triangledown}

Djalal Meziane-Cherif,1,{dagger} Dominique Decré,2 E. Arne Høiby,3 Patrice Courvalin,1* and Bruno Périchon1

Unité des Agents Antibactériens, Institut Pasteur, 75724 Paris Cedex 15,1 Hôpital Saint-Antoine, 184, Rue Fbg. St. Antoine, 75012 Paris, France,2 Department of Bacteriology, National Institute of Public Health, P.O. Box 4404, NO-0403 Oslo, Norway3

Received 30 August 2007/ Returned for modification 24 October 2007/ Accepted 28 November 2007

Carnobacterium divergens clinical isolates BM4489 and BM4490 were resistant to penicillins but remained susceptible to combinations of amoxicillin-clavulanic acid and piperacillin-tazobactam. Cloning and sequencing of the responsible determinant from BM4489 revealed a coding sequence of 912 bp encoding a class A β-lactamase named CAD-1. The blaCAD-1 gene was assigned to a chromosomal location in the two strains that had distinct pulsed-field gel electrophoresis patterns. CAD-1 shared 53% and 42% identity with β-lactamases from Bacillus cereus and Staphylococcus aureus, respectively. Alignment of CAD-1 with other class A β-lactamases indicated the presence of 25 out of the 26 isofunctional amino acids in class A β-lactamases. Escherichia coli harboring blaCAD-1 exhibited resistance to penams (benzylpenicillin and amoxicillin) and remained susceptible to amoxicillin in combination with clavulanic acid. Mature CAD-1 consisted of a 34.4-kDa polypeptide. Kinetic analysis indicated that CAD-1 exhibited a narrow substrate profile, hydrolyzing benzylpenicillin, ampicillin, and piperacillin with catalytic efficiencies of 6,600, 3,200, and 2,900 mM–1 s–1, respectively. The enzyme did not interact with oxyiminocephalosporins, imipenem, or aztreonam. CAD-1 was inhibited by tazobactam (50% inhibitory concentration [IC50] = 0.27 µM), clavulanic acid (IC50 = 4.7 µM), and sulbactam (IC50 = 43.5 µM). The blaCAD-1 gene is likely to have been acquired by BM4489 and BM4490 as part of a mobile genetic element, since it was not found in the susceptible type strain CIP 101029 and was adjacent to a gene for a resolvase.

* Corresponding author. Mailing address: Unité des Agents Antibactériens, Institut Pasteur, 25 Rue du Docteur Roux, 75724 Paris Cedex 15, France. Phone: (33) (1) 45 68 83 20. Fax: (33) (1) 45 68 83 19. E-mail: pcourval{at}pasteur.fr

{triangledown} Published ahead of print on 10 December 2007.

{dagger} Present address: Laboratoire de Biochimie Appliquée, Faculté des Sciences, Université Ferhat Abbas, 19000 Sétif, Algeria.

Antimicrobial Agents and Chemotherapy, February 2008, p. 551-556, Vol. 52, No. 2
0066-4804/08/$08.00+0     doi:10.1128/AAC.01145-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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