RESUMO
The submicroscopic structure of surfaces in the streptococci of group B, type III (strain 13/63) and the ultrastructure of the interaction of this streptococcus strain with human vaginal cells were studied. The surface of the majority of B streptococci was smooth after using the conventional fixing techniques of electron microscopy; however, about 25% of streptococcal cells had an additional layer of filamentous protrusions on their surface. A marked layer of capsular material was visualized by means of the preincubation of this streptococcus strain with a type-specific antiserum. The incubation of B streptococci with vaginal cells without any addition of antibody allowed for the demonstration of the contact of a part of the cells of the bacterial population with the epithelial cells through filamentous protrusions. However, the majority of the smooth-surface cells was separated from vaginal cells by a gap wide up to 150 nm. It was demonstrated by additional incubation with type-specific antiserum that the above mentioned gap corresponded to the capsular substance of bacteria. Hence the capsule of streptococci in group B is the basic component of their surface responsible for adherence to vaginal cells. Adherence of B streptococci to vaginal epithelia was accompanied neither by bacterium ingestion nor by the destruction of epithelial cells.
