Typing of Streptococcus agalactiae (Lancefield group B)

Area of Science:

• Microbiology
• Infectious Diseases
• Epidemiology

Background:

• Group B streptococci (GBS) are a significant cause of neonatal infections.
• Current typing methods for GBS have limitations in discrimination and typability.
• Understanding GBS transmission is crucial for preventing neonatal disease.

Purpose of the Study:

• To describe and evaluate a two-stage typing scheme for routine laboratory use.
• To investigate the sources of GBS infections in early neonatal life.
• To differentiate between human and bovine GBS strains.

Main Methods:

• A two-stage typing strategy combining serotyping and phage-typing for GBS strains.
• Analysis of GBS strain characteristics, including antigen profiles and phage lysis patterns.
• Epidemiological correlation of GBS infections with maternal flora and other potential sources.

Main Results:

• Serotyping alone showed limited discriminatory power due to common antigens (Ia/c, III/R) in nearly 40% of strains.
• Phage-typing had a typability rate below 80%, indicating limitations in its application.
• Evidence suggests early-onset GBS infections (<5 days) primarily stem from maternal flora acquisition.
• Human and bovine GBS strains represent distinct populations with identifiable antigenic and biochemical differences.
• No specific phage lysis patterns were found to characterize either human or bovine GBS strains.

Conclusions:

• The combined serotyping and phage-typing scheme provides a more comprehensive approach to GBS characterization.
• Early-onset GBS infections are strongly linked to maternal transmission.
• Distinct populations of human and bovine GBS exist, differentiated by non-phage-based methods.