Open AccessChromosome-Encoded Narrow-Spectrum Ambler Class A β-Lactamase GIL-1 from Citrobacter gillenii
Author(s) -
Thierry Naas,
Daniel Aubert,
Ayla Özcan,
Patrice Nordmann
Publication year - 2007
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.01152-06
Subject(s) - biology , gene , microbiology and biotechnology , escherichia coli , gene duplication , genetics , citrobacter , nucleic acid sequence , clavulanic acid , peptide sequence , dna , consensus sequence , enterobacteriaceae , amoxicillin , antibiotics
A novel β-lactamase gene was cloned from the whole-cell DNA of an enterobacterialCitrobacter gillenii reference strain that displayed a weak narrow-spectrum β-lactam-resistant phenotype and was expressed inEscherichia coli . It encoded a clavulanic acid-inhibited Ambler class A β-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 β-lactamases TEM-1 and SHV-1. Thebla GIL-1 gene was chromosomally located, as revealed by I-CeuI experiments, and was constitutively expressed at a low level inC. gillenii . No gene homologous to the regulatoryampR genes of chromosomal class C β-lactamases was found upstream of thebla GIL-1 gene, which fits the noninducibility of β-lactamase expression inC. 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 inE. coli . Thebla GIL-1 gene was part of a 5.5-kb DNA fragment bracketed by a 9-bp duplication and inserted between thed -lactate dehydrogenase gene and theydbH genes; this DNA fragment was absent in otherCitrobacter species. This work further illustrates the heterogeneity of β-lactamases inCitrobacter spp., which may indicate that the variability ofCitrobacter species is greater than expected.