The diversity of bacterial pathogenicity mechanisms

One of the remarkable features of the recent FEMS meeting on the molecular basis of bacterial pathogenesis was the novel ways in which genome sequences are now being used to study bacterial pathogens. In the 10 years since the first complete sequence of the genome of a pathogenic bacterium - that of Haemophilus influenzae - was published, the genomes of almost all the major human pathogens have been sequenced. The first and most obvious use of these data was comparative genome analysis in order to understand what distinguishes pathogenic from nonpathogenic strains. While this approach continues to be useful for discovering new genes that cause disease (virulence genes, which are possible targets for new antibacterial drugs) and clusters of virulence genes (pathogenicity islands) in the genome, and for providing clues to how pathogens have evolved, several new approaches to using genome data were presented at the meeting. These include the development of new vaccines (reverse vaccinology), uncovering new biosynthetic pathways, studying how bacteria adapt rapidly to new environments and the beginning of a comprehensive comparison of genomics and proteomics.Virulent strains of Escherichia coli can be divided into two classes: those that cause intestinal disease and those causing disease elsewhere in the body (extra-intestinal strains). Extra-intestinal E. coli (ExPEC strains) are the cause of a diverse spectrum of invasive human and animal infections, often leading to septicemia. Joerg Hacker (Institut für Molekulare Infektionsbiologie, Würzburg, Germany) reported the analysis of the genomes of a number of pathogenic and commensal E. coli strains. Each genome could be divided into the 'core genome' and the 'flexible gene pool'; the latter comprises up to one third of the entire genome. For example, the uropathogenic E. coli strain 536 contains six pathogenicity islands, comprising more than 500 kb in total. These islands show a characteristic genetic architecture and d