Molecular characterization and outbreak analysis of multidrug-resistant Acinetobacter baumannii from German hospitals

Abstract number: P797

Objectives: Emergence and dissemination of multidrug-resistant Acinetobacter baumannii are of special concern because of limited therapeutic options and increased mortality. In many cases colistin is the only antimicrobial substance for an adequate treatment. In Germany A. baumannii outbreaks were observed mainly in the summer months. Here we report on molecular-epidemiological analysis of A. baumannii from different German hospitals.

Methods: The strain collection includes 22 isolates from two outbreaks in one hospital (A) in 2007 as well as 42 outbreak isolates collected in a surgical ICU (hospital B) in 2006–2008. Furthermore 32 isolates (2005–2009) from two diagnostic laboratories were analysed. Molecular typing by PFGE and sequence-based multiplex PCR to identify isolates belonging to members of the European clonal complexes I-III were performed. Relevant resistance genes (blaOXA, blaVIM and blaIMP) were identified by PCR and sequencing.

Results: All above mentioned isolates were resistant to fluoroquinolones, aminoglycosides, sulfonamides and b-lactams including carbapenems. PCR and sequencing of resistance genes revealed the presence of OXA-b-lactamases in all isolates, with OXA-23 (n = 45) and OXA-58 (n = 47) as the most prevalent types. In several outbreak-independent isolates the genes blaOXA-72 (n = 1), blaOXA-58+blaOXA-23 (n = 1) or blaOXA-66 + insertion sequence ISAba1 were identified. In one single carbapenem-resistant isolate no carbapenemase gene was found.

Multiplex-PCR analysis for identification of clonal lineages revealed that nearly all isolates are related to the European clones I (n = 19), II (n = 51) and III (n = 2). Outbreak analysis of hospital A showed three different clones (PFGE-macrorestriction patterns) whereby eight identical isolates with OXA-23 are related to the European clone II (multiplex-typing). The index-patients were repatriated from hospitals in Turkey and Egypt. In hospital B the 27 isolates from 2006 and 2007 had identical PFGE patterns and contained OXA-58. However, in 2008 a new A. baumannii clone with OXA-23 was detected. Two patients died from an infection with this strain.

Conclusion: Infections with multidrug-resistant A. baumannii are still rare in Germany. The strains were imported by patients after return from abroad and further spread was probably due to transmission by staff or contaminated medical equipment. This highlights the need for the implementation of strict hygiene control measures or even isolation.