Serotypes, hemolysin production, and receptor recognition of Escherichia coli strains associated with neonatal sepsis and meningitis.

Sixty-three Escherichia coli strains isolated from neonatal sepsis or meningitis were studied and compared with previous data on fecal or urinary pyelonephritis-associated isolates from children. Characteristics significantly associated with neonatal infection were capsular type K1 (54%), O group 18 (27%), rough-type lipopolysaccharide together with K1 capsule (19%), and S fimbriae (29%). Within the neonatal infection group, the K1 capsule and rough lipopolysaccharide were most common among the youngest infants (0 to 21 days old) and in meningitis. Hemolysin production, P fimbriae, and X adhesions (adhesions not identifiable as type 1, P, or S) were significantly more common in the two materials from infections as compared with the fecal isolates. One large clone of 11 strains (O18:K1:H7, with both type 1 and S fimbriae) and three smaller ones (O7:K1:H1 and O6:K2:H1, both with type 1 and P fimbriae and X adhesions; and R:K1:H33 with no adhesions) were identified among the strains from neonatal infections. Only O6:K2:H1 strains were also common among the strains from pyelonephritis.