Low virulence of Escherichia coli strains causing urinary tract infection in renal disease patients.

ABSTRACT

The distribution of urinary bacterial species was determined and the virulence factors of Escherichia coli urinary strains analysed by molecular and phenotyping methods in episodes of urinary tract infection in renal disease patients (n =68) in comparison with other immunocompromised patients (n =59) and non-immunocompromised patients (n =21). Escherichia coli was isolated in 116 (78%) of the 148 patients, being the species most frequently isolated in all groups (75% of renal disease patients, 76% of other immunocompromised patients, 95% of non-immunocompromised patients). All other pathogens showed a similar distribution in the renal disease and other immunocompromised patient groups. All virulence factors of Escherichia coli tested for (genes for G adhesins, expression of MR adhesins, production of haemolysin, presence of certain O and K antigens) were found more often in non-immunocompromised than in immunocompromised patients. The factors allowing the highest degree of discrimination between immunocompromised and non-immunocompromised patients were the prevalence of genes for G adhesins (35% vs. 65%) and expression of MR adhesins (32% vs. 55%). It is concluded that there is a lower prevalence of G adhesins and MR adhesins in Escherichia coli strains from immunocompromised patients than non-immunocompromised patients, suggesting that less virulent Escherichia coli strains may cause urinary tract infections more frequently in renal disease patients and other immunocompromised patients. Moreover, the spectrum of urinary pathogens other than Escherichia coli is similar in both immunocompromised patient groups investigated.