Virulent and Avirulent Strains of Group B Streptococci from Rio de Janeiro, Brazil: Relationship between Differences in Surface Hydrophobicity, Sialic Acid Content and Macrophage Interaction Leia mais sobre Virulent and Avirulent Strains of Group B Streptococci from Rio de Janeiro, Brazil: Relationship between Differences in Surface Hydrophobicity, Sialic Acid Content and Macrophage Interaction