Genetic and biochemical characterization of GES-5, an extended-spectrum class A β-lactamase from Klebsiella pneumoniae

The present study was conducted to characterize a new class I integron containing the bla(GES-5) gene cassette in Klebsiella pneumoniae clinical isolate CHAK36 and measure the kinetic parameters of GES-5 beta-lactamase. Long-range polymerase chain reactions (PCRs) and sequence analysis were performed to identify and analyze the bla(GES-5) gene cassette-containing integrons. Kinetic parameters were determined from purified GES-5. Sequencing of the 6190-bp PCR amplicon from K pneumoniae CHAK36 isolate revealed the new structure of class 1 integron. The integron has 3 unique gene cassettes (bla(GEs-5)-aac(6')-IIa-bla(OXA-17)/orf4), but the 59-base element of the bla(OXA-17) gene cassette was interrupted by a putative transposase gene, orf4. The kinetic parameters of GES-5 showed its broad-spectrum activity against most beta-lactams, including benzylpenicillin, cefaloridine, cefotaxime, and imipenem. This work shows that the bla(GES-5) gene was located on a new class I integron as a gene cassette. Our kinetic characterizations show that GES-5 was more active against impenem than GES-2 and GES-4. (c) 2007 Elsevier Inc. All rights reserved.