Serological variation in oral Streptococcus milleri.

Area of Science:

• Microbiology
• Immunology
• Oral Health

Background:

• Streptococcus milleri group bacteria are common in the human oral cavity.
• Accurate classification of oral streptococci is crucial for understanding their role in health and disease.
• Existing classification methods for Streptococcus milleri have limitations.

Purpose of the Study:

• To develop and validate a novel serotyping scheme for oral isolates of Streptococcus milleri.
• To investigate the correlation between the new serotyping scheme and existing biotyping methods.
• To determine the distribution of Streptococcus milleri serotypes in dental plaque.

Main Methods:

• Raised antisera in rabbits against selected Streptococcus milleri strains.
• Used double diffusion in agar gel to serotype 71 oral isolates and 3 reference strains.
• Compared the new serotyping results with previously established biotyping schemes.
• Analyzed the distribution of serotypes in dental plaque samples from young adults.

Main Results:

• A new serotyping scheme successfully divided 70 out of 71 oral Streptococcus milleri isolates into 10 distinct serotypes (a-j) based on cell-surface carbohydrate antigens.
• The proposed serotyping scheme targets type antigens distinct from Lancefield group antigens, though serotypes a, c, and f correlated with Lancefield groups A, C, and F.
• A strong correlation was observed between the new serotyping scheme and a previously proposed biotyping scheme for Streptococcus milleri.
• Four strains were found to be untypable by this scheme.

Conclusions:

• The developed serotyping scheme provides a reliable method for classifying oral Streptococcus milleri isolates.
• This serotyping approach complements existing biotyping methods and enhances bacterial identification.
• The study provides insights into the prevalence and diversity of Streptococcus milleri serotypes in dental plaque ecosystems.