Frequency of E. coli K antigens in urinary-tract infections in children.

The somatic (O) and casular (K) antigens of Escherichia coli from the urine of patients with acute pyelonephritis, acute cystitis, and asymptomatic bacteriuria, and in the faeces of healthy schoolchildren have been investigated. Typing antisera for sixteen capsular acidic polysaccharide K antigens were used, and five (numbers 1, 2, 3, 12, and 13) accounted for 70% of isolates from patients with acute pyelonephritis. These five K antigens were found to a lesser extent in the three other study groups. Thus, only a few K polysaccharides are associated with virulent properties of E. coli for the upper urinary tract. This finding is similar to the association of only some capsular types of pneumococci, meningococci, and Haemophilus influenzae with invasiveness. The identification of virulence markers for E. coli associated with upper-urinary-tract disease may permit more successful control with reference to preventive immunisation.