The molecular study of bacterial virulence: a review of current approaches, illustrated by the study of adhesion in uropathogenic Escherichia coli.

Pathogenic bacteria coexist with their hosts in a relationship which most frequently allows persistence of the bacteria without causing disease. In a small proportion of colonised individuals the complex mutual interaction between microbe and host is upset, leading to disease in the host. The investigation of bacterial virulence determinants and their genetic control at the molecular level is an important facet of the development of strategies to combat disease. This review focuses on the investigation of a single pathogenic organism as a means of illustrating modern approaches to the investigation of bacterial virulence. The importance of uropathogenic Escherichia coli in causing acute and recurrent pyelonephritis with the consequent morbidity of chronic renal failure is well established. Pyelonephritis-associated (Pap) pili are likely to be critical virulence factors in uropathogenic E. coli. The evidence for their role in pathogenicity and the control of their expression at the molecular genetic level is discussed.