Group B streptococcus late-onset disease: 2003-2010.

BACKGROUND There is insufficient population-based data on group B streptococcus (GBS) late-onset disease (LOD). Risk factors and routes of GBS transmission are poorly understood. METHODS A prospective, cohort study was conducted to collect incidence data on LOD and evaluate GBS infections over an 8-year period (2003-2010). Starting from January 2007, maternal rectovaginal and breast milk cultures were routinely collected on confirmation of the LOD diagnosis to assess maternal GBS culture status. RESULTS The incidence rate of LOD was 0.32 per 1000 live births (1.4 and 0.24 per 1000 live births for preterm and term newborns, respectively). The registered cases of LOD (n = 100) were classified as sepsis (n = 57), meningitis (n = 36), or focal infection (n = 7). Thirty neonates were preterm (2 had recurrent infection); 68 were term. Four infants died (3 early preterm, 1 term). At the time the LOD diagnosis was confirmed, 3 (6%) of 53 mothers had GBS mastitis, and 30 (64%) of 47 carried GBS at the rectovaginal site. Early (7-30 days) LOD presentation was associated with neonatal brain lesions or death (odds ratio: 0.96 [95% confidence interval: 0.93-0.99]). Intrapartum antibiotic exposure was significantly associated with mild (12 of 22) rather than severe (11 of 45; P = .03) LOD. CONCLUSIONS Preterm neonates had the highest rates of LOD and mortality. Most mothers carried GBS at the time of the LOD diagnosis, whereas 6% had mastitis. Intrapartum antibiotics were associated both with delayed presentation of symptoms and milder LOD.