[Role of hyaluronic acid in the virulence of group A streptococci].

The effect of hyaluronic acid and hyaluronidase on the virulent properties of group A streptococci in mice were studied. The passage of streptococci belonging to different serotypes in mice was accompanied by a considerable increase of their virulence and the accumulation of hyaluronic acid. The electron microscopy of the initial and passaged strains allowed one to reveal the presence of considerable differences in their cell wall structure. The passaged strains had a pronounced filamentous and sharply thickened medium layer containing hyaluronic acid. The treatment of passaged streptococci of the infected mice with hyaluronidase did not induce decrease of virulence in the passaged cultures. The data obtained indicate that hyaluronic acid is not a virulence factor for mice. Such virulence may be determined by some component, not yet identified, of the filamentous layer of the cell wall in group A streptococci.