Relationship between O serotype and virulent genes in Escherichia coli causing urinary tract infections.

Background: Escherichia coli are the most frequent pathogens in acute urinary infections. They are classified based on various types of O antigen. Escherichia coli strains that cause urinary tract infections possess several genes encoding urovirulent factors. To assay the relation of virulent factors of E coli in acute urinary infections, the serotypes and virulence factor genotypes were determined.

Methods: We studied 96 E coli isolates from children with acute urinary infections. Four urovirulence determinants were analyzed by DNA colony hybridization, including the genes for type 1 fimbriae (pil), P fimbriae (pap), S fimbriae (sfa), hemolysin (hly), and cytotoxic necrotizing factor 1 (cnf1). O serotypes were also determined.

Results: The most frequently found virulence factor-encoding gene in the E coli strains studied was the gene for type 1 fimbriae (27.4%). The prevalence of pap, sfa, hly, and cnf1 were higher in serotypes causing pyelonephritis than cystitis. The most common type of O antigen was O1 (12.2%). There was a significant correlation between serotype and genotype in uropathogenic E coli.

Conclusions: The high prevalence of O6 serotypes in children urinary tract infections and the high percentage of virulent genes in serotype O6 suggested a close relation between serotype and genotypes of uropathogen E coli.