Periodontal disease, which affects the support structures and protection of teeth, is the main disease found in dogs, reaching about 85% prevalence in animals over 4 years old. The most important bacteria in the initial colonization of human dental plaque are Streptococcus, which produce exopolysaccharides that facilitate fixation of the bacteria to the surfaces. Some studies have sought to identify the dental plaque microbiota in dogs using non-selective culture media, and have reported small amounts of Streptococcus, however they did not provide ideal conditions for the growth of this bacteria. The aim of this study was to isolate and identify the initial dental plaque microbiota of dogs cultivable in a selective medium for Streptococcus, and verify the presence of this genus. Genotypic identification of the isolates were carried out by partial 16S rDNA sequencing. A total of 179 strains were obtained from the plaque of 10 dogs without periodontal disease. The technique employed allowed 15 different microbial groups to be isolated, including the genus Streptococcus. This represented 33 (18.4%) of 179 isolates, thus illustrating the partially selective ability of Mitis Salivarius Agar for samples of dental plaque in dogs.