Use of representational difference analysis to identify Escherichia coli O157-specific DNA sequences

Whereas several important virulence factors in Escherichia coli O157 have b een identified, studies suggest they are not always essential and are proba bly insufficient to account for the severe clinical manifestation of E. col i O157 infection. Identification of putative virulence determinants is cruc ial to the understanding of bacterial pathogenesis and genomic comparison a nalysis may aid the characterisation of unidentified virulence attributes. In this study, representational difference analysis (RDA) was used for geno mic comparison of E. coli O157 with the proposed ancestral strain. E. coli O55. Unique E. coli O157 gene sequences were isolated and one, termed RDA-1 , taken forward for Further analysis, Southern blotting with labelled RDA-1 as a probe showed it to be present in 77% of E. coli O157 isolates and abs ent in all non-E. coli O157 screened. Sequence flanking RDA-L was obtained from a genomic clone identified by hybridisation. and contained an open rea ding frame predicted to encode a novel iron-regulated outer membrane protei n. (C) 2001 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.