Representatives (n = 31) of outbreak strains of Acinetobacter baumannii from five countries fell into three clear groups, designated Groups 1-3, based on their ompA (outer-membrane protein A), csuE (part of a pilus assembly system required for biofilm formation) and bla(OXA-51-like) (the intrinsic carbapenemase gene in A. baumannii) gene sequences. With the exception of the closely related alleles within the Group 1 clonal complex, alleles at each locus were highly distinct from each other, with a minimum of 14 nucleotide differences between any two alleles. Isolates within a group shared the same combination of alleles at the three loci, providing compelling evidence that the outbreak strains investigated belonged to three clonal lineages. These corresponded to the previously identified European clones I-III. Sequence differences among the alleles were used to design multiplex PCRs to rapidly assign isolates belonging to particular genotypes to sequence groups. In the UK, genotypes belonging to the Group 1 clonal complex have been particularly successful, accounting for the vast majority of isolates referred from hospitals experiencing problems with Acinetobacter.

The magA gene was sought in hypermucoviscous isolates of Klebsiella spp., the Klebsiella K serotype reference strains and in isolates of the K1 serotype of Klebsiella pneumoniae from the UK, Hong Kong, Israel, Taiwan and Australia. Only K1 isolates were PCR positive for magA; this gene was found in all such isolates tested. Hypermucoviscosity was not confined to magA positive isolates, nor was it found in all magA positive isolates. Comparison of XbaI PFGE profiles revealed that most (19/23) of the magA positive isolates clustered within 72 % similarity, with a further subcluster of isolates, from three different continents, clustering within .80 %. All of the 16 isolates tested within the main cluster had the same sequence type (ST 23) by multilocus sequence typing, with the exception of one isolate, which had a single nucleotide difference at one of the seven loci. This study indicates that a genotype strongly associated with highly invasive disease in Taiwan, where large numbers of cases have been reported, is geographically very widespread.