Capsular polysaccharide of Group B Streptococcus mediates biofilm formation in the presence of human plasma

Group B Streptococcus (GBS) is an asymptomatic colonizer of human mucosal surfaces that is responsible for sepsis and meningitis in neonates. Bacterial persistence and pathogenesis often involves biofilm formation. We previously showed that biofilm formation in medium supplemented with glucose is mediated by the PI-2a pilus. Here, biofilm formation was tested in cell culture medium supplemented with human plasma. GBS strains were able to form biofilms in these conditions unlike Group A Streptococcus (GAS) or Staphylococcus aureus. Analysis of mutants impaired for various surface components revealed that the GBS capsule is a key component in this process.