Niska virulencija sojeva Escherichia coli - uzročnika egzarcebacije kroničnog pijelonefritisa

SUMMARYEscherichia (E.) coli, which causes over 80% of uncomplicated urinary tract infections, may simultaneously express a number of virulence factors of relevance for urinary tract infections. Some of the recognized E. coli virulence factors are adherence to uroepithelial cells, certain O and K serotypes, hemolysin production, and aerobactin production. One of E. coli adhesins, P-fimbriae, are known as a major virulence factor in the development of acute uncomplicated pyelonephritis. The aim of this study was to determine the virulence properties of E. coli strains isolated from the urine of patients with chronic pyelonephritis, and to compare them to the properties of strains isolated from patients with acute pyelonephritis, acute cystitis, and asymptomatic bacteriuria. For each strain, O-serogroup, adhesin type, motility, production of hemolysin, and the amount of capsular polysac- charide were examined. The strains isolated from patients with acute pyelonephritis were found to mostly express all five or four virulence markers tested, while the less virulent strains were detected in the group of patients with chronic pyelonephritis, where most strains expressed up to three viru- lence markers. The lowest virulence was observed among the strains isolated in the group of patients with asymptomatic bacteriuria. Expression of P-fimbriae and production of hemolysin were found to be the most important virulence factors with the highest power for discrimination between chronic and acute upper urinary tract infection (p<0.01).