Naas_2007_Antimicrob.Agents.Chemother_51_1365

A novel beta-lactamase gene was cloned from the whole-cell DNA of an enterobacterial Citrobacter gillenii reference strain that displayed a weak narrow-spectrum beta-lactam-resistant phenotype and was expressed in Escherichia coli It encoded a clavulanic acid-inhibited Ambler class A beta-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 beta-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 beta-lactamases was found upstream of the blaGIL-1 gene which fits the noninducibility of beta-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 beta-lactamases in Citrobacter spp which may indicate that the variability of Citrobacter species is greater than expected.