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Multi-centre study of dissemination and diversity of carbapenem-resistant Acinetobacter baumannii Spanish clinical isolates

Abstract number: P1703

Head J., Culebras E., Andrade R., Gómez M., Picazo J.

Objectives: To investigate the differences in antimicrobial susceptibility and clonal relatedness against carbapenem-resistant Acinetobacter baumannii collected in several Spanish Hospitals in two different time period (from 15-April-1998 to 17-November-1998 and from January to February 2006).

Methods: A total of 93 imipenem-resistant A. baumannii were collected from 25 general hospitals in Spain in 1998 (44 isolates) and 2006 (49 isolates). Species identification and antibiotic susceptibilities were determined by Vitek-2. MICs were determined by microdilution, agar dilution methods and E-test (tigecylcine and colistin). Clonal relatedness was determined by RAPD-PCR and ERIC2-PCR. E-test with imipenem (IMP) and imipenem plus EDTA was performed to check metallo-b-lactamase (MBL) production. The isolates were screened by PCR analysis with specific primers for carbapenemase genes.

Results: Epidemiologic relatedness of 44 imipenem-resistant isolates from 1998, revealed only 4 different genetic backgrounds. In the isolates from the second period, the four original clones are maintained and 4 new profiles, closely related with previous ones, were identified. Overall, 100%A. baumannii isolates were resistant to >3 antimicrobials classes. All the isolates carried a gene encoding a b-lactamase belonging to OXA-51-like group. 15 of the 44 isolates (34.1%) from 1998 and 13 of the 49 isolates (26.5%) from 2006 contained the insertion sequence ISAba1 upstream the promoter region of the blaOXA-51-like gene. 66% of the isolates from 1998 carried a gene encoding an OXA-40-like enzyme, alone (21 isolates) or combined with an IMP carbapenemase (8 isolates). In 2006, OXA-40-like oxacillinase was the enzyme prevalent (22 isolates; 18 isolates alone, 4 combined with another enzyme) but OXA-58-like and OXA-23-like enzymes were detected in a significant percentage of isolates (28.6% and 18.4% respectively). Some degree of heterogeneity was observed within each genetic background. This heterogeneity was higher in groups from 2006 than in groups from 1998.

Conclusions: Several clones among A. baumannii multirresistant isolates are maintained over the time in Spanish hospitals. The predominant clones appeared in most than one hospital indicating possible inter-hospital spread of carbapenem resistant A. baumannii strains. OXA-40-like enzyme, is the enzyme prevalent at Spanish hospitals.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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