Molecular characterization of In50, a class 1 integron encoding the gene for the extended-spectrum β-lactamase VEB-1 in Pseudomonas aeruginosa

A clinical isolate of Pseudomonas aeruginosa, JES, was resistant to extended-spectrum cephalosporins with a marked synergistic effect with clavulanic acid on a routine antibiogram. Preliminary PCR analysis revealed the presence of bla(VEB-1), an integron-located gene encoding an extended-spectrum p-lactamase previously identified in Escherichia coli MG-1. Using class 1 integron primers and bla(VEB-1) intragenic primers, the insert region of the bla(VEB-1) containing integron along with some flanking sequence from P. aeruginosa JES was amplified and subsequently sequenced. In50 contains within its variable region, in addition to qacE Delta 1 and sul1 genes commonly found in class 1 integrons, two gene cassettes, veb1 and aadB. In50 is peculiar since its attl1 site is interrupted by two novel insertion sequences, IS1999 and IS2000. P. aeruginosa JES and Escherichia coli MG-1 strains were isolated from patients previously hospitalized in south east Asian countries. The finding of bla(VEB-1) in these strains and on different integrons underlines the interspecies spread of this integron-located extended-spectrum beta-lactamase gene. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.