Genomic Surveillance and Vaccine Coverage of Pediatric Invasive Group B Streptococcus in Japan

Overview

A nationwide genomic study of 237 pediatric invasive Group B Streptococcus (GBS) isolates in Japan revealed high estimated vaccine coverage of 98.3% for the hexavalent polysaccharide vaccine and 94.9% for the GBS-NN/NN2 protein vaccine. Multidrug-resistant clones, particularly within the CC17 lineage, were prevalent, with significant erythromycin and clindamycin resistance observed.

Background

Group B Streptococcus (GBS) is a major cause of neonatal and infant invasive infections such as sepsis and meningitis. Despite intrapartum antibiotic prophylaxis reducing early-onset disease, late-onset and very late-onset infections remain a challenge, partly due to unclear transmission routes beyond vertical maternal transmission. Maternal vaccination targeting capsular polysaccharides or conserved protein antigens is a promising strategy to prevent invasive GBS disease in infants. Understanding the genomic characteristics and vaccine coverage of circulating pediatric GBS strains is critical to inform prevention strategies.

Data Highlights

Key Findings

• High estimated coverage of pediatric invasive GBS isolates by current maternal vaccine candidates: 98.3% for hexavalent polysaccharide and 94.9% for GBS-NN/NN2 protein vaccines.
• Significant antimicrobial resistance observed: 61.2% erythromycin and 43.5% clindamycin resistance among isolates.
• Predominance of a multidrug-resistant CC17 clone characterized by presence of PI-2B pilus island and resistance genes ermB and tetO.
• Single nucleotide polymorphism analysis revealed evidence of nosocomial transmission and persistent regional circulation, especially within ST17 and ST23 lineages.
• Potential transmission routes beyond vertical maternal transmission suggested, including environmental reservoirs and caregiver contact.
• Genomic surveillance highlights the importance of monitoring circulating GBS clones to guide vaccine implementation and infection control.

Clinical Implications

The high vaccine coverage estimates support the potential effectiveness of current maternal GBS vaccines in preventing invasive pediatric infections in Japan. However, the widespread antimicrobial resistance, particularly to erythromycin and clindamycin, underscores the need for ongoing surveillance and cautious antibiotic use. Identification of persistent multidrug-resistant clones and evidence of nosocomial transmission highlight the importance of infection control measures and further investigation into non-maternal transmission pathways.

Conclusion

This comprehensive genomic analysis demonstrates broad vaccine coverage against pediatric invasive GBS in Japan while revealing the persistence of multidrug-resistant clones and complex transmission dynamics. These findings inform future vaccine strategies and emphasize the need for integrated surveillance and prevention efforts.

References

1. WHO 2021 -- GBS vaccine development and implementation milestones
2. Berardi et al. 2018 -- Maternal colonization and late-onset GBS disease
3. Phase I GBS-NN/NN2 vaccine trial 2022 -- Safety and immunogenicity