[Genetic approach to the virulence of bacteria]

Bacteria only possess a single chromosome, but they also contain prophages, plasmids and transposons. The genetic basis for the pathogenic power of invasive and toxigenic bacteria only represents a small part of the total genotype of these bacteria. It is curious that although the plasmids and the prophages only represent about 1 p. cent of the total genome, they are disproportionately responsible for carrying the genetic information concerning virulence. The genetic study of virulence has revealed new mechanisms of pathogenic activity, for example the interaction of siderophores, adherence factors and haemolysins in pathogenic activity. Furthermore, the understanding of the genetic basis of virulence will lead to new methods of diagnosis and a new generation of vaccines.