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Antimicrobial Agents and Chemotherapy, April 2007, p. 1365-1372, Vol. 51, No. 4
0066-4804/07/$08.00+0     doi:10.1128/AAC.01152-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Chromosome-Encoded Narrow-Spectrum Ambler Class A ß-Lactamase GIL-1 from Citrobacter gillenii{triangledown}

Thierry Naas,* Daniel Aubert, Ayla Özcan, and Patrice Nordmann

Service de Bactériologie-Virologie, Hôpital de Bicêtre, Assistance Publique-Hôpitaux de Paris, Faculté de Médecine Paris-Sud, 94275 Le Kremlin-Bicêtre, France

Received 14 September 2006/ Returned for modification 13 October 2006/ Accepted 8 January 2007

A novel ß-lactamase gene was cloned from the whole-cell DNA of an enterobacterial Citrobacter gillenii reference strain that displayed a weak narrow-spectrum ß-lactam-resistant phenotype and was expressed in Escherichia coli. It encoded a clavulanic acid-inhibited Ambler class A ß-lactamase, GIL-1, with a pI value of 7.5 and a molecular mass of ca. 29 kDa. GIL-1 had the highest percent amino acid sequence identity with TEM-1 and SHV-1, 77%, and 67%, respectively, and only 46%, 31%, and 32% amino acid sequence identity with CKO-1 (C. koseri), CdiA1 (C. diversus), and SED-1 (C. sedlaki), respectively. The substrate profile of the purified GIL-1 was similar to that of ß-lactamases TEM-1 and SHV-1. The blaGIL-1 gene was chromosomally located, as revealed by I-CeuI experiments, and was constitutively expressed at a low level in C. gillenii. No gene homologous to the regulatory ampR genes of chromosomal class C ß-lactamases was found upstream of the blaGIL-1 gene, which fits the noninducibility of ß-lactamase expression in C. gillenii. Rapid amplification of DNA 5' ends analysis of the promoter region revealed putative promoter sequences that diverge from what has been identified as the consensus sequence in E. coli. The blaGIL-1 gene was part of a 5.5-kb DNA fragment bracketed by a 9-bp duplication and inserted between the D-lactate dehydrogenase gene and the ydbH genes; this DNA fragment was absent in other Citrobacter species. This work further illustrates the heterogeneity of ß-lactamases in Citrobacter spp., which may indicate that the variability of Citrobacter species is greater than expected.

* Corresponding author. Mailing address: Service de Bactériologie-Virologie, Hôpital de Bicêtre, 78 rue du Général Leclerc, 94275 Le Kremlin-Bicêtre Cédex, France. Phone: 33 1 45 21 29 86. Fax: 33 1 45 21 63 40. E-mail: thierry.naas{at}bct.ap-hop-paris.fr

{triangledown} Published ahead of print on 22 January 2007.

Antimicrobial Agents and Chemotherapy, April 2007, p. 1365-1372, Vol. 51, No. 4
0066-4804/07/$08.00+0     doi:10.1128/AAC.01152-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Jacoby, G. A. (2009). AmpC {beta}-Lactamases. Clin. Microbiol. Rev. 22: 161-182 [Abstract] [Full Text]  


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