Colonization and cariogenicity of Streptococcus ferus in rats

Area of Science:

• Microbiology
• Oral Health
• Dental Caries Research

Background:

• Streptococcus ferus is a species indigenous to wild rats and belongs to the mutans streptococci group.
• The cariogenic potential of S. ferus compared to known pathogens like Streptococcus sobrinus is not well-established.

Purpose of the Study:

• To evaluate the colonization ability and cariogenic potential of Streptococcus ferus in a rat model.
• To compare the in vivo performance of S. ferus strains against a highly cariogenic S. sobrinus strain.

Main Methods:

• Two strains of S. ferus and one strain of S. sobrinus were inoculated into laboratory rats.
• Rats were maintained on either a standard chow diet or a high-sucrose diet, with some groups switched between diets.
• Colonization levels, proportions of oral flora, plaque formation, and caries development were assessed.

Main Results:

• All tested streptococcal strains successfully colonized the rats' oral cavities irrespective of diet.
• High-sucrose diets increased the proportion of infectant bacteria in the oral flora.
• S. ferus formed plaques but less extensively than S. sobrinus and did not induce caries, unlike S. sobrinus.

Conclusions:

• Streptococcus ferus colonizes the oral cavity but is non-cariogenic in rats, even on a sucrose-rich diet.
• Limited plaque proliferation on smooth tooth surfaces and reduced acid production likely contribute to the lack of cariogenicity in S. ferus.
• S. ferus may naturally lack the pathogenic potential typically associated with mutans streptococci.