title: Genetic structure associated with blaOXA-18, encoding a clavulanic acid-inhibited extended-spectrum oxacillinase.
abstract: The genetic environment of the bla(OXA-18) gene encoding a peculiar clavulanic acid-inhibitable Ambler class D extended-spectrum beta-lactamase was determined from the prototype OXA-18-producing Pseudomonas aeruginosa MUS clinical isolate. An 8.2-kb genomic DNA fragment containing bla(OXA-18) was cloned from P. aeruginosa MUS. Although most oxacillinases are located in integrons, bla(OXA-18) lacked gene cassette-specific features. It was bracketed by two duplicated sequences containing ISCR19, a novel insertion sequence of the ISCR family of mobile elements; DeltaintI1, a truncated integrase gene; and a truncated Deltaaac6'-Ib gene cassette. It is likely that ISCR19 was at the origin of the bla(OXA-18) gene mobilization by a rolling-circle transposition event followed by homologous recombination. Furthermore, analysis of the cloned genomic DNA fragment revealed the presence of the integron-containing bla(OXA-20) gene. Concomitantly, three P. aeruginosa clinical isolates, displaying a synergy image as determined by double-disk diffusion tests on cloxacillin-containing plates, were isolated from three patients hospitalized in different wards over a 9-month period at the Saint-Luc University hospital (Brussels, Belgium). These isolates were positive by PCR for bla(OXA-18) and bla(OXA-20) genes, genetically related to P. aeruginosa MUS as determined by pulsed-field gel electrophoresis, and carried the same bla(OXA-18)/bla(OXA-20)-associated genetic structures. This report characterized the genetic elements likely at the origin of bla(OXA-18) gene mobilization in P. aeruginosa and suggests the spread of oxacillin-type extended-spectrum beta-lactamases in P. aeruginosa at the Saint-Luc University hospital of Brussels, Belgium.
authors.affiliation: Service de Bactériologie-Virologie, INSERM U914, Hôpital de Bicêtre, Le Kremlin-Bicêtre Cedex, France. thierry.naas@bct.aphp.fr
authors.forename: Thierry
authors.initials: T
authors.lastname: Naas
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Namdari
authors.forename: Pierre
authors.initials: P
authors.lastname: Bogaerts
authors.forename: Te-Din
authors.initials: TD
authors.lastname: Huang
authors.forename: Youri
authors.initials: Y
authors.lastname: Glupczynski
authors.forename: Patrice
authors.initials: P
authors.lastname: Nordmann
mesh_terms: D001483:Base Sequence; D001530:Belgium; D002874:Chromosome Mapping; D019818:Clavulanic Acid / Q000494:pharmacology*; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D006801:Humans; D032023:Integrons; D008957:Models, Genetic; D008969:Molecular Sequence Data; D011552:Pseudomonas Infections / Q000188:drug therapy / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics* / Q000302:isolation & purification; D012689:Sequence Homology, Nucleic Acid; D024363:Transcription Initiation Site; D018440:beta-Lactam Resistance / Q000235:genetics; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial; D065093:beta-Lactamase Inhibitors; D019818:Clavulanic Acid; D001618:beta-Lactamases; C108449:oxacillinase