Factors affecting virulence in Escherichia coli urinary tract infections.

The prevalence of E. coli relative to other bacteria in the urinary tract is assumed to be the result of its proximity to and its close relationship with the gastrointestinal tract. Strains on E. coli may establish themselves more readily in the urinary tract, and/or invade the upper urinary tract, if they have a number of different virulence factors. The relative importance of these factors in the development of urinary tract infection, with or without renal involvement, is not clear. In addition, the means by which these factors may increase the virulence of E. coli are not understood, although there seems to be some evidence that the K antigens alter resistance to phagocytosis and serum bactericidal activity %9,10]. The main reason that certain E. coli serotypes are cultured from the urinary tract, however, still seems to be their dominance in the stool. The broader question of why certain O serotypes of E. coli dominate the bowel flora has not been examined adequately. The studies suggesting that the K antigen is a significant virulence factor seem to be in conflict with other studies indicating the dominance of certain serotypes of E. coli in the stool and in urinary tract infections. A resolution of this dilemma may possibly be found in the recent observations of Dr. Frits Orskov [20] and others discussed elsewhere at this meeting that the K and O serotypes appear to be interrelated.