title: Integrase-mediated recombination of the veb1 gene cassette encoding an extended-spectrum β-lactamase.
abstract: The veb1 gene cassette encodes the extended spectrum β-lactamase, VEB-1 that is increasingly isolated from worldwide Gram-negative rods. Veb1 is commonly inserted into the variable region of different class 1 integrons in which it is always associated with a downstream-located aadB gene cassette encoding an aminoglycoside adenylyltransferase. In Pseudomonas aeruginosa, the majority of veb1-containing integrons also carry an insertion sequence, IS1999 that is inserted upstream of the veb1 gene cassette and disrupts the integron specific recombination site, attI1. Investigation of the recombination properties of the sites surrounding veb1 revealed that insertion of IS1999 reduces significantly the recombination frequency of attI1 and that veb1 attC is not efficient for recombination in contrast to aadB attC. Subsequent sequence optimisation of veb1 attC by mutagenesis, into a more consensual attC site resembling aadB attC, successfully improved recombination efficiency. Overall, this work gives some insights into the organisation of veb1-containing integrons. We propose that IS1999 and the nature of veb1 attC stabilize the veb1 gene cassette environment likely by impairing recombination events upstream or downstream of veb1, respectively.
authors.affiliation: Service de Bactériologie-Virologie, INSERM U914 "Emerging Resistance to Antibiotics," LabEx LERMIT, Hôpital de Bicêtre, Assistance Publique/Hôpitaux de Paris, Faculté de Médecine Université Paris-Sud, Paris, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Aubert
authors.forename: Thierry
authors.initials: T
authors.lastname: Naas
authors.forename: Patrice
authors.initials: P
authors.lastname: Nordmann
mesh_terms: D001287:Attachment Sites, Microbiological / Q000235:genetics; D001483:Base Sequence; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D029968:Escherichia coli Proteins; D019426:Integrases / Q000378:metabolism*; D032023:Integrons / Q000235:genetics; D016254:Mutagenesis, Insertional / Q000235:genetics*; D009690:Nucleic Acid Conformation; D016133:Polymerase Chain Reaction; D011550:Pseudomonas aeruginosa / Q000201:enzymology* / Q000235:genetics*; D011995:Recombination, Genetic; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D019426:Integrases; C119424:beta-lactamase VEB-1, E coli; D001618:beta-Lactamases