Virulence-associated traits in Escherichia coli causing first and recurrent episodes of urinary tract infection in children with or without vesicoureteral reflux.

Virulence-associated properties of 606 urinary isolates from 174 children with urinary tract infections were related to severity of infection and factors increasing host susceptibility, e.g., vesicoureteral reflux (grade II or higher) and P1 blood group phenotype. A high proportion of strains of Escherichia coli causing first or recurrent episodes of acute pyelonephritis in children without reflux expressed the previously noted high frequency of certain O antigens, resistance to serum killing, hemolysin production, and adhesive capacity. A significantly lower frequency of these traits and a higher frequency of non-E. coli were seen among isolates from children with pyelonephritis and reflux, cystitis, and asymptomatic bacteriuria. Reflux was thus found to be a determinant of the level of infection and of the bacterial properties required to produce pyelonephritis. Efforts aimed at preventing or treating urinary tract infection by interfering with "virulent" bacteria may be of less value in patients with recurrent pyelonephritis and reflux, who are most likely to develop renal scars.