Aerobactin-mediated uptake of iron by strains of Escherichia coli causing acute pyelonephritis and bacteraemia

A total of 285 strains of Escherichia coli isolated from children and women with acute non-obstructive pyelonephritis and from patients with bacteraemia as well as 120 faecal strains of E. coli from healthy children and adults were examined for aerobactin-mediated uptake of iron. The incidence of aerobactin-positive strains was significantly more in isolates from children with acute pyelonephritis (81%) than in faecal isolates from healthy children (50%, P less than 0.01). It was also higher in isolates of E. coli from women with acute pyelonephritis (72%) compared with faecal isolates from healthy adults (42%, P less than 0.001). Of the E. coli strains causing bacteraemia, 55% were aerobactin-positive. A significant correlation was found between the presence of aerobactin and expression of P-fimbriae in strains of E. coli isolated from children with acute pyelonephritis (P less than 0.01) and in isolates from bacteraemic patients (P less than 0.001). These results indicate that the presence of an aerobactin-mediated system of iron uptake may be an important virulence factor in strains of E. coli that cause ascending pyelonephritis.