Outbreak of carbapenem-resistant Acinetobacter baumannii isolates producing the carbapenem-hydrolysing oxacillinase OXA-97 (OXA-58-like) in a university hospital in Tunisia

Abstract number: 1732_335

Poirel L., Mansour W., Bouallegue O., Boujaafar N., Nordmann P.

Objective: To characterise the clonal relationship and the b-lactamase content of carbapenem-resistant Acinetobacter baumannii isolates recovered in a University Hospital in Tunisia (Sousse) during a four-year period.

Methods: Forty-six non-repetitive carbapenem-resistant Acinetobacter baumannii isolates were recovered during the October 2001–October 2005 period from urine, pus, broncheal and blood samples. The presence of oxacillinase or metallo-b-lactamase genes was performed by PCR, cloning and sequencing. In particular, genes coding for the carbapenem-hydrolyzing oxacillinases (CHDL) OXA-23, OXA-40 and OXA-58 subgroups were searched. Genotyping was done by pulsed field gel electrophoresis (PFGE) after ApaI restriction.

Results: The A. baumannii isolates were mostly from patients hospitalised in intensive care units. MICs determination allowed to divide these isolates into two main phenotypical groups, both being resistant to most b-lactams including carbapenems. Twenty-two A. baumannii isolates possessed the blaOXA-97 gene encoding the novel carbapenem-hydrolysing oxacillinase OXA-97 differing from OXA-58 by a single amino acid substitution (Gly to Ala at position DBL35). OXA-97 exhibits the same hydrolysis profile as OXA-58, hydrolysing penicillins and carbapenems but sparing expanded-spectrum b-lactams. Genotyping revealed that the OXA-97-positive A. baumannii isolates belonged to a single clone, although six distinct genotypes were identified thus defining subclones. The blaOXA-97 gene was located on plasmids varying in size and they were all transferred to an A. baumannii reference strain by electroporation, whereas mating-out assays were unsuccessful. Only one isolate harboured the blaOXA-97 gene on its chromosome.

The other twenty-four carbapenem-resistant A. baumannii isolates did not produce any carbapenemase and they did not possess any CHDL gene. They were clonally related according to PFGE analysis.

Conclusion: This study constitutes the first description of dissemination of a CHDL enzyme in Africa and reports on the identification of the novel OXA-97 being closely related to OXA-58. As observed for OXA-58 in other countries, the gene coding for OXA-97 was mostly located on plasmids and identified in A. baumannii isolates being the source of an outbreak. Interestingly, this epidemiological survey showed that outbreaks of two different carbapenem-resistant A. baumannii strains had occurred in that hospital during the same period of time.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
Back to top