S. mutans from dog oral cavity was transmitted from human

Objectives: Dental caries is one of the most common human oral diseases and has been described in a variety of domestic animals. The dog is a close companion in many human families. The purpose of this study is to isolation and identification of mutans streptococci from dog oral cavity. Methods: Oral samples from 68 family dogs were cultured on Mitis Salivarius medium under candle jar conditions. Gram-positive streptococcal mutans-like strains were isolated and identified by biochemical and serological testing and extensive 16S rRNA sequencing, G+C content, DNA-DNA homology. The cariogenicity of isolates was also examined. Results: Two typical S. mutans-like colonies from 2 dogs were isolated on MS agar plate from dog oral cavities. The strains formed small, raised, irregular in margin and adherent colonies. Both strains were grouped in serotype c of mutans streptococci and identified S. mutans by biochemical test using Rapid ID 32STREP identification kit. The strains were also identical to S. mutans by DNA-DNA hybridization, GC contents and 16S rRNA gene sequencing analyses. To determine the origin of the strains, oral samples of their owners were examined. DNA-DNA hybridization showed that the percent homology of the isolates between dog and owner was more than 90%. The cariogenicity of the isolated from dogs was similar that of S. mutans of owners. These results indicated that two isolates from dogs were identical the S. mutans from their owners. Conclusion: This study shows that S. mutans from dog oral cavity was transmitted from the owner and human S. mutans can colonize in dog oral cavity. Dog individual mutans streptococci including S. mutans were not detected.