Invasive Escherichia coli infections in children: bacterial characteristics in different age groups and clinical entities.

Escherichia coli isolates from blood or cerebrospinal fluid of 135 children were characterized for serotype, adhesin and hemolysin production and compared with 94 fecal isolates from healthy children. Capsular type K1, sero-group O18 and rough-type lipopolysaccharide were predominant in neonatal infections (49, 16 and 16%, respectively) and also in meningitis and septicemia of infants from 7 days to 23 months of age (39, 17 and 13%). S-fimbriated strains were common in neonatal infections (23%) but rare (< or = 5%) in all other clinical groups. Pyelonephritis was the most common diagnosis in infants (49 of 72); it was associated with P-fimbriation (63%); serogroups O1, O2, O4, O6 or O7 (41%), and hemolysin production (37%). Invasive infections in older children (age > or = 2 years) were associated with predisposing factors and were caused by strains resembling fecal isolates; the only exception was hemolysin production which was detected in 40% of the disease but only 9% of the fecal isolates. Eight O:K:H serotypes were associated with invasive infections; they usually had K1 or K5 capsule and either P, S or type 1C fimbriae.