Streptococcus mutans clonal variation revealed by multilocus sequence typing.

Area of Science:

• Microbiology
• Genetics
• Infectious Diseases

Background:

• Streptococcus mutans is a primary cause of dental caries and can lead to infective endocarditis.
• S. mutans strains are classified into serotypes c, e, f, and k.
• Understanding the population structure and clonal relationships of S. mutans is crucial for identifying strains causing systemic diseases.

Purpose of the Study:

• To develop and apply a multilocus sequence typing (MLST) scheme for S. mutans.
• To investigate the population diversity and clonal relationships among S. mutans strains.
• To determine the ancestral serotype and geographic distribution of S. mutans strains.

Main Methods:

• Sequencing of eight housekeeping gene fragments from 102 S. mutans isolates across four serotypes.
• Analysis of sequence data to identify alleles and sequence types.
• Phylogenetic analysis (dendrogram) to assess clonal relationships.

Main Results:

• Identified 92 distinct sequence types among 102 isolates, indicating high S. mutans population diversity.
• Serotype c strains were broadly distributed, while serotypes e, f, and k formed distinct clonal complexes.
• No significant geographic specificity was observed, but the collagen-binding protein gene (cnm) distribution and mother-to-child transmission were evident.

Conclusions:

• The developed MLST scheme offers high discriminatory power for S. mutans.
• Serotype c is likely the ancestral serotype of S. mutans.
• The findings have practical implications for understanding S. mutans epidemiology and pathogenesis.