title: High prevalence of carbapenem-hydrolysing oxacillinases in epidemiologically related and unrelated Acinetobacter baumannii clinical isolates in Spain.
abstract: Carbapenem-hydrolysing oxacillinases are reported increasingly in Acinetobacter baumannii. This study investigated the role of these beta-lactamases in causing resistance to carbapenems in 83 epidemiologically related and unrelated imipenem-resistant A. baumannii clinical isolates. The isolates were also analysed for the presence of ISAba1 in the promoter region of the bla(OXA-51)-like gene in order to investigate the role of ISAba1 in OXA-51 expression. All clinical isolates contained a bla(OXA-51)-like gene, 20% contained a bla(OXA-58)-like gene, and 42% contained a bla(OXA-40)-like gene; bla(OXA-23)-like, bla(IMP) and bla(VIM) genes were not detected in any of the isolates investigated. ISAba1 was found in 24 (82.7%) of 28 pulsetypes, and was located in the promoter region of the bla(OXA-51)-like gene in five (20.8%) of these pulsetypes. Expression of bla(OXA-51) was detected in the five isolates with ISAba1 located in the promoter region, but was not detected in an isogenic imipenem-susceptible A. baumannii isolate that did not have ISAba1 located in the promoter region. It was concluded that there is a high prevalence of oxacillinases with activity against carbapenems among genetically unrelated A. baumannii clinical isolates from Spain, and that concomitant expression of two carbapenemases (OXA-51-like and either OXA-40-like or OXA-58-like) may take place. Insertion of an ISAba1-like element in the promoter of the bla(OXA-51)-like gene promotes the expression of this gene, although this did not seem to play a major role in carbapenem resistance.
authors.affiliation: Servei de Microbiologia, Centre de Diagnòstic Biomèdic, Hospital Clinic, IDIBAPS, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Ruiz
authors.forename: S
authors.initials: S
authors.lastname: Marti
authors.forename: F
authors.initials: F
authors.lastname: Fernandez-Cuenca
authors.forename: A
authors.initials: A
authors.lastname: Pascual
authors.forename: J
authors.initials: J
authors.lastname: Vila
mesh_terms: D000151:Acinetobacter Infections / Q000453:epidemiology / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000145:classification / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D005838:Genotype; D006801:Humans; D015378:Imipenem / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D013030:Spain / Q000453:epidemiology; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D015378:Imipenem; D001618:beta-Lactamases; C108449:oxacillinase