Early neonatal group B streptococcal disease: degree of colonisation as an important determinant.

During a period of 5 years (1 January 1977 to 1 January 1982) 145 infants colonised with group B streptococci (GBS) were admitted to the neonatal intensive care unit of the University Children's Hospital, Utrecht. In 87 of these infants (60%) vertical transmission of GBS was established; in 43 of these 87 infants (49%) the degree of colonisation was moderate to heavy. Early-onset (EO) GBS disease arose in 21 of 145 infants (attack rate: 14.5%). Of the 43 infants moderately to heavily colonised with GBS, however, 19 suffered from EO GBS disease (attack rate: 44.2%), whereas there were only two cases among the 44, lightly colonised infants (attack rate: 4.5%), a highly significant difference (P less than 0.0005). Similarly, probable sepsis (PS), defined as signs and symptoms of sepsis but without positive blood cultures, was observed significantly more often in moderately to heavily colonised infants (15/43, attack rate: 34.9%) compared with those lightly colonised (4/44, attack rate: 9.1%) (P less than 0.005). Infants moderately to heavily colonised with GBS at birth appear to have a significantly higher risk of developing serious GBS disease (EO or PS) than do infants only lightly colonised.