Nosocomial dissemination of carbapenem-resistant Acinetobacter spp. isolates in a general hospital in Thessaloniki, Greece

Abstract number: P1509

Figueiredo S., Poirel L., Papa A., Koulourida V., Nordmann P.

Objectives: To characterise the clonal relationship and the b-lactamase content of carbapenem-resistant Acinetobacter spp. isolates recovered in a University Hospital in Thessaloniki, Greece.

Methods: Twenty-one non-repetitive carbapenem-resistant Acinetobacter spp. isolates were recovered from August 2001 to November 2006 period at the Papageorgiou General Hospital, Thessaloniki, Greece. Species identification was determined by the biochemical API32 GN test (bio-Mérieux, France) and by 16S rRNA sequencing. Susceptibility testing was done by disk diffusion method and Minimum Inhibitory Concentration (MICs) were determined by agar dilution. Genes coding for the carbapenem-hydrolyzing class D b-lactamases OXA-23, OXA-40, OXA-58 and OXA-51 subgroups and for VIM- and IMP-type metallo-b-lactamases (MBLs) were searched. The isolates were also screened for the presence of ISAba1 in the promoter region of the blaOXA-51-like gene in order to investigate the role of ISAba1 in blaOXA-51 expression. Genotyping was done by pulsed field gel electrophoresis (PFGE) after digestion by ApaI.

Results: All isolates were identified as A. baumannii except one isolate identified as Acinetobacter genomospecies 16. Genotyping revealed that the twenty A. baumannii isolates belonged to five different pulsed-field gel electrophoresis clones. Clones 1 to 3 including sixteen A. baumannii isolates harboured the blaOXA-58 gene whereas clones 4 and 5 including four isolates did not possess any carbapenemase gene. ISAba1 was identified upstream of the blaOXA-51 gene in three blaOXA-58 negative A. baumannii isolates. In one of these isolates, ISAba1 was truncated immediately upstream of the blaOXA-51 gene by a novel insertion sequence named ISAba9 that may provide promoter sequences for blaOXA-51 expression. Acinetobacter genomospecies 16 harboured VIM-4 MBL determinant. The blaOXA-58 gene was most often plasmid-located.

Conclusion: This study highlights the diversity of the mechanisms involved in carbapenem resistance in an Acinetobacter spp. Furthermore, this is the first description of the MBL VIM-4 determinant in Acinetobacter spp. and the first description of ISAba9, a novel insertion sequence providing promoters for oxacillinase genes expression.