Related Experiment Video
Updated: Jun 29, 2026
A Murine Model of Group B Streptococcus Vaginal Colonization
Published on: November 16, 2016
Protective effect of hyaluronidase and type-specific anti-M serum on experimental group A streptococcus infection in
Abstract:
Five strains of encapsulated group A streptococci of different serological types, each with a glossy and a matt variant, were studied to compare the rôles of the M substance and the hyaluronic acid capsule in virulence of these microorganisms. The results indicated that both contribute to the virulence of group A streptococci but that the M antigen is the more fundamental factor. Encapsulated variants, both glossy and matt, were slightly less susceptible to phagocytosis than those from which the capsule had been removed with hyaluronidase. Glossy variants, containing no M substance, were readily phagocyted; matt, M-containing variants were resistant to phagocytosis except in the presence of anti-M serum when they became fully susceptible. Only the M-containing, matt strains were mouse-virulent. Mice were protected against infections with these strains: (a) By removal of the capsule with hyaluronidase, which resulted in slight protection, but only against 10 M.L.D. Early and intensive treatment was required to produce this effect; i.e., simultaneous injection of enzyme and streptococci followed by prolonged enzyme therapy. (b) By a single injection of anti-M serum administered the day before inoculation of the streptococci, which resulted in protection against 100,000 M.L.D. (c) By combined use of enzyme and anti-M serum, an additive effect of the two protective agents occurred, which resulted in protection against 1,000,000 M.L.D.
Insights
Group A streptococci virulence depends on M substance and hyaluronic acid capsules, with M substance being crucial. Both factors contribute to bacterial survival, but M substance offers greater protection against host defenses.
Area of Science:
- Microbiology
- Immunology
- Pathogenesis
Background:
- Group A streptococci (GAS) are significant human pathogens.
- Virulence factors, including M protein and hyaluronic acid capsule, are critical for GAS survival and pathogenesis.
- Understanding the interplay of these factors is essential for developing effective countermeasures.
Purpose of the Study:
- To compare the roles of M substance and hyaluronic acid capsule in the virulence of different GAS serotypes.
- To investigate the impact of these virulence factors on phagocytosis and mouse models of infection.
Main Methods:
- Studied five GAS strains with glossy (non-M substance) and matt (M substance) variants.
- Assessed susceptibility to phagocytosis with and without hyaluronidase treatment.
- Evaluated mouse virulence and protection conferred by hyaluronidase and anti-M serum.
Main Results:
- Both M substance and hyaluronic acid capsule contribute to GAS virulence, with M substance being the primary factor.
- Encapsulated GAS were less susceptible to phagocytosis; M-containing matt strains were resistant unless anti-M serum was present.
- Only M-containing matt strains exhibited mouse virulence, with significant protection achieved using anti-M serum.
Conclusions:
- M substance is a fundamental virulence factor in group A streptococci, conferring resistance to phagocytosis.
- Hyaluronic acid capsule provides a lesser degree of protection against phagocytosis and host defenses.
- Anti-M serum is a highly effective protective agent against virulent M-containing GAS strains.
