Pathogenic diversity of Escherichia coli and the emergence of 'exotic' islands in the gene stream

Escherichia coli is a highly adaptive bacterial species that is both a memb er of the commensal intestinal flora and a versatile pathogen associated wi th numerous types of intestinal and systemic infections in humans and other animals. The spectrum of diseases caused by E. coli is due to the acquisit ion of specific virulence genes harbored on plasmids, bacteriophages, or wi thin distinct DNA segments termed pathogenicity islands (PAIs) that are abs ent from the genomes of commensal E. coli strains. PAIs are likely to have been transferred horizontally and may have integrated into the E. coli chro mosome through bacteriophage or plasmid integration or transposition. The c ontribution of intergenic inheritance to the adaptation and evolution of E. coli, types of PAIs associated with different groups of pathogenic E. coli and approaches to identify unique sequence islands (USIs), some of which m ight confer pathogenicity, in E. coli and other bacteria are presented. (C) Inra/Elsevier, Paris.