Long-term dissemination of an OXA-40 carbapenemase-producing Acinetobacter baumannii clone in the Iberian Peninsula

Objective: The main objectives of this study were to assess the clonal relatedness of Acinetobacter baumannii carbapenem-resistant isolates recovered from the Iberian Peninsula and to investigate the production of carbapenemases. Methods: One hundred and sixty-two imipenem-resistant A. baumannii isolates were collected from 1998 to 2003 in three Portuguese university hospitals. An imipenem-resistant isolate (988FFP strain) recovered in 1995 from a smaller hospital unit, was also included, as well as an OXA-40-producing A. baumannii Spanish strain (SM28). Susceptibility tests were carried out by disc diffusion and Etest methods. DNA fingerprints were obtained by PFGE of ApaI-digested chromosomal DNA. Carbapenemase activity was determined by a bioassay and spectrophotometry. The detection of the bla(OXA-40) gene was conducted through PCR analysis, cloning and nucleotide sequencing. Results: All the isolates presented a similar multi-resistance pattern, including imipenem (MIC >32 mg/L). The Iberian isolates showed an identical PFGE pattern with minor band variations, including isolate 988FFP collected in 1995. PCR results revealed a bla(OXA)-type gene in 65 isolates and nucleotide sequence analysis revealed the presence of the bla(OXA-40) gene in seven representative Portuguese isolates from the various geographically dispersed hospitals. Conclusions: Our results indicate that a multi-resistant epidemic clone of A. baumannii, carrying bla(OXA-40), is disseminated in the Iberian Peninsula, persisting in Portugal since 1995.