Virulence factors of uropathogenic Escherichia coli strains isolated from children with chronic pyelonephritis

Background. Urinary tract infection (UTI) is one of the most common bacterial infections among children. Chronic pyelonephritis is a renal injury induced by recurrent or persistent renal infection. The severity of the UTI depends both on the virulence of the infecting bacteria and the susceptibility of the host. Uropathogenic Escherichia coli (UPEC) strains display a variety of virulence factors that help to colonize host mucosal surfaces and circumvent host defenses to allow invasion of the normally sterile upper urinary tract. Objectives. The purpose of this study was to determine the occurrence of virulence factors among UPEC isolates. Material and Methods. Sixty-six E. coli strains isolated from the urine of children with chronic pyelonephritis were tested for mannose-resistant hemagglutination in order to indicate P fimbriae. Cell-surface hydrophobicity was assayed by two methods: the bacterial adhesion to hydrocarbon-xylene test (BATH) and the salt aggregation test (SAT). The ability to adhesion was directly measured by using uroepithelial cells. The bacteriophage K1A was used to detect the presence of the capsular antigen K1. The production of a-hemolysin was assessed using blood agar. Results. Among the isolates studied, the prevalence of the virulence factors a-hemolysin, hydrophobicity, P fimbriae, adhesion to uroepithelium, and K1 capsule were 77%, 74%, 42%, 42%, and 29%, respectively. Most of the E. coli strains (37.9%) expressed two virulence factors. Conclusions. Hydrophobicity and the production of alpha-hemolysin in E. coli strains are important virulence factors in the pathogenesis and development of chronic pyelonephritis.