The Streptococcus agalactiae R3 surface protein is encoded by sar5

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Vaccinology

Background:

• Streptococcus agalactiae (group B Streptococcus; GBS) causes severe infections in neonates and other vulnerable populations.
• GBS surface proteins are crucial for vaccine development and epidemiological serotyping.
• The genetic origin of some GBS surface markers, like the R3 protein, remains unknown.

Purpose of the Study:

• To identify the gene responsible for the R3 surface protein in Streptococcus agalactiae.
• To establish a genetic basis for a known GBS serotype marker.
• To facilitate future vaccine design and improve GBS strain characterization.

Main Methods:

• Analysis of a Norwegian collection of 140 GBS strains.
• Correlation of R3 protein expression with the presence of the sar5 gene.
• Inducible expression of the sar5 gene in an R3-negative bacterial strain.
• Confirmation using R3 monoclonal antibody recognition.

Main Results:

• R3 protein expression in GBS was found to correlate with the presence of the sar5 gene.
• Inducible expression of sar5 resulted in a product recognized by the R3 monoclonal antibody.
• The sar5 gene was identified as the genetic determinant of the R3 surface protein.

Conclusions:

• The sar5 gene encodes the R3 surface protein in Streptococcus agalactiae.
• This identification provides a genetic basis for the R3 serotype marker.
• The findings support the development of GBS vaccines and enhance epidemiological surveillance.