Prospective study of peripartum group B streptococcus colonization in Japanese mothers and neonates.

Group B streptococcus (GBS) is a major global cause of neonatal, infant, and maternal infections. In Japan, national guidelines based on Centers for Disease Control and Prevention recommendations mandate culture-based screening and intrapartum antibiotic prophylaxis (IAP) for GBS-positive pregnant women. Despite initial reductions in GBS infections, the incidence has plateaued, and there are notable limitations in current prevention methods. Approximately 15% of pregnant women are not screened for GBS, and intermittent colonization undermines screening accuracy, contributing to early-onset disease. IAP does not prevent late-onset disease, the incidence of which is increasing in Japan. This study reviewed maternal and neonatal GBS colonization using polymerase chain reaction, evaluated capsular type distributions, and explored late-onset disease infection routes. Among 525 mother-neonate pairs, the study found a higher detection rate of GBS via polymerase chain reaction compared to culture methods and identified significant discrepancies between antepartum and intrapartum colonization. GBS was detected in 3.5% of neonates from initially negative mothers at 4 days of age. Capsular types varied between mothers and neonates, indicating potential horizontal transmission. This study underscores the need for improved rapid diagnostic tests and highlights the potential of maternal GBS vaccination as a future prevention strategy.