UROPATHOGENIC PROPERTIES OF ESCHERICHIA COLI IN RECURRENT URINARY-TRACT INFECTION

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Abstract
ESCHERICHIA COLI is the pathogen most commonly isolated in urinary-tract infections (UTI). It is thought that E. coli from the gut colonise the periurethral area, extend into the anterior urethra and are introduced into the bladder during micturition. Imperfections in the host defence mechanisms allow bacteria to multiply in the bladder urine and, in some cases, to cause an ascending infection of the kidney (O'Grady et al., 1970). Unless urinary-tract infection differs from infection elsewhere in the body it is likely that some strains of E. coli possess properties that enable them to overcome host defences more easily. Numerous reports have examined whether certain serotypes of E. coli are more common in UTI simply because they are more common in the faeces or because they possess specific uropatho-genic properties. The properties that might be implicated in the pathogenesis of UTI include: (1) the ability to colonise the urinary tract by the production of mucinase that enables the organisms to reach the uroepithelium, or the possession of fimbriae that allow adhesion to the mucosal surface; (2) preferential nutritional requirements for substances present in urine or relative resistance to urinary inhibitors such as urea or low p H; (3) resistance to phagocytosis and the serum bactericidal system; (4) the elaboration of toxins. We studied several properties that may influence the pathogenicity of E. coli strains and compared their occurrence in strains isolated from (i) the urine of patients with UTI, (ii) the urethral meatus of nephrourological patients without current UTI and (iii) the urethral meatus of normal subjects.

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