Adherence and surface properties of buoyant density subpopulations of group B streptococci, type III

From clinical isolates of group B streptococci, buoyant density subpopulations with variable amounts of type-specific polysaccharide can be derived. The ability of these subpopulations to adhere to vaginal epithelial cells and to glass was assessed by using [3H]-labeled bacteria. Subpopulations with no or minute amounts of capsule showed good adherence capacity and a hydrophobic cell surface. In contrast, a large capsule made the bacteria less adherent and rendered their surface hydrophilic. A negative cell surface charge, judged by determination of the z-potential, was directly related to the amount of capsule. Proteinase K treatment of less encapsulated variants significantly decreased the cell hydrophobicity. The ability of a GBS strain to express different surface characteristics may be a mechanism for adaptation to environmental changes, and may thereby contribute to the pathogenicity of GBS.