1040 ENUMERATION OF GROUP B STREPTOCOCCI (GBS) IN COLONIZED INFANTS

Abstract

It is unknown why only 1 in 100 colonized infants develop GBS disease. There have been several semiquantitative studies of colonization in mothers, but no quantitative studies on magnitude of colonization in infants. This study was designed to determine if infants symptomatic for early-onset GBS disease (respiratory distress) are heavily colonized with the bacteria. Newborn infants suspected of early-onset disease at Tampa General Hospital were cultured at three or more sites with CulturetteR dual swabs. The swabs were used for identification of GBS by slide co-agglutination and enumeration of the bacteria by viable plate count. Eleven (13%) of 85 infants cultured were found to be colonized with GBS at one or more sites. Two of these eleven colonized infants were symptomatic for early-onset GBS disease. Both symptomatic infants were heavily colonized (≥2.9 × 103 bacteria/swab) with GBS of serotype I. In comparison, only one of the nine asymptomatic infants was colonized with GBS of serotype I and the colonization was of a low magnitude (<2.0 × 101 bacteria/swab). The other eight infants were colonized with nontype I GBS, generally at low numbers. The two asymptomatic infants that were heavily colonized with GBS were colonized with bacteria of serotype III. These preliminary data suggest a possible correlation between heavy colonization of neonates with specific serotypes of GBS and the development of early-onset group B disease.