Long-term predominance of two pan-European clones among multi-resistant Acinetobacter baumannii strains in the Czech Republic

In a recent study, a large proportion of multi-drug-resistant (MDR) Acinetobacter baumannii strains that were isolated from hospitalized patients in the Czech Republic was found to belong to two major groups (A and B). These groups appeared to be similar to epidemic clones I and 11, respectively, which were identified previously among outbreak strains from north-western European hospitals. The aim of the present study was to assess in detail the genetic relatedness of Czech A. baumannii strains and those of epidemic clones I and II by using ribotyping with HindIII and HincII and by AFLP fingerprinting. The study collection included 70 MDR strains that were isolated in 30 Czech hospitals in 1991 - 2001, 15 susceptible Czech strains from 1991 to 1996 and 13 reference strains of clones I and II from 1982 to 1990. One major HindIII/HincIII ribotype (R1-1) was observed in 38 MDR Czech strains and eight reference strains of clone I, whereas another major ribotype (R2-2) was observed in 11 MDR Czech strains and in three reference strains of clone II. A selection of 59 Czech strains (representative of all ribotypes) and the 13 reference strains were investigated by AFLP fingerprinting. At a clustering level of 83%, two large clusters could be distinguished: cluster 1 included all reference strains of clone I and 25 MDR Czech strains, whilst cluster 2 contained all reference strains of clone II and 11 MDR Czech strains. There was a clear correlation between the groupings by AFLP analysis and by ribotyping, as all strains with ribotype R1-1 and four strains with slightly different ribotypes were found in AFLP cluster 1, whereas all strains with ribotype R2-2 and seven strains with similar ribotypes were in AFLP cluster 2. Thus, 41 and 21 MDR Czech strains could be classified as belonging to clones I and II, respectively. The remaining eight MDR and 15 susceptible strains were highly heterogeneous and were distinct from clones I and II by both AFLP fingerprinting and ribotyping. These results indicate that the two predominant groups observed among MDR Czech A. baumannii strains from the 1990s are genetically congruent with the northwestern European epidemic clones that were found in the 1980s. Recognition of these clinically relevant, widespread clones is important in infection prevention and control; they are also interesting subjects to study genetic mechanisms that give rise to their antibiotic resistance and epidemic behaviour.