PROPERTIES OF ESCHERICHIA COLI IN RECURRENT URINARY TRACT INFECTION.

Abstract

Properties of Escherichia coli considered to be of importance in overcoming host defence mechanisms against urinary tract infection (OTI) were investigated. These were: 1) 0 and H serotype 2) K antigen content 3) Sensitivity to the bactericidal activity of human serum 4) Haemolysin production 5) Fimbriae production 6) Fermentation of sucrose, salicin and dulcitol 7) Sensitivity to serine, spermine and urea 8) Growth requirements 9) Mucinase production

Ecoli strains isolated from normal subjects and patients attending the Nephrourological Clinic at St. Bartholomew's Hospital because of known or suspected UTI, were studied. Strains isolated from urines more frequently belonged to 0 serogroups 2,4,6,8,18ab and 75, had high K antigen titres, were haemolytic and fimbriate, and fermented salicin than periurethral strains from normal subjects. These findings support the concept of "special pathogenicity", that certain strains are more invasive for the urinary tract than others. Strains rich in these "pathogenic properties" were rarely isolated from normal subjects but were significantly more frequently isolated from periurethral swabs of patients. Periurethral strains from symptomatic, abacteriuric (urethral syndrome) patients were similar to those from bacteriuric patients when they were between infections. Previous work has not implicated bacteria in the aetiology of most cases of this disease and this finding remains unexplained. Strains isolated from the upper tracts of patients undergoing localisation tests more frequently exhibited pathogenic properties than those isolated from only the lower tract, and this was considered to reflect the superior ability of these strains to reach the upper tract or better combat host defence mechanisms.