Population genetics of group B

Area of Science:

• Microbiology
• Genetics
• Public Health

Background:

• Group B Streptococcus (GBS) is a leading cause of neonatal infections.
• Maternal immunization is a promising strategy to prevent GBS disease.
• Understanding GBS population structure in pregnant women is crucial for vaccine development.

Purpose of the Study:

• To characterize the population structure of GBS isolates from maternal carriage in London.
• To identify prevalent GBS serotypes and clonal complexes (CCs) relevant for vaccine targets.
• To investigate antimicrobial resistance patterns and their association with GBS lineages and maternal ethnicity.

Main Methods:

• Whole genome sequencing of 535 GBS isolates from maternal carriage.
• Analysis of population structure, serotypes, and virulence/resistance genes.
• Statistical analysis of associations between GBS characteristics, maternal ethnicity, and antimicrobial resistance.

Main Results:

• Five major GBS lineages (CC1, CC19, CC23, CC17, CC8/10) comprised 95% of isolates.
• Serotypes III, V, II, and Ia were most common.
• High prevalence of alpha family protein genes (99%) and macrolide-lincosamide-streptogramin B (MLSB) resistance genes (22%).
• Significant associations observed between maternal ethnicity and GBS serotype/lineage distribution.
• Clarithromycin (21%) and clindamycin (13%) resistance detected.

Conclusions:

• GBS isolates from pregnant women in London show high prevalence of vaccine targets.
• Specific lineages (CC1, CC19) harbor serotype diversity and antimicrobial resistance, posing challenges.
• These high-risk lineages may act as reservoirs for non-vaccine strains and resistance determinants.