Objetivou-se determinar a microbiota da placa bacteriana subgengival de cães com doença periodontal (DP) e estabelecer o efeito da antibioticoterapia. Avaliaram-se 20 cães com graus variados de DP e coletaram-se amostras da placa bacteriana subgengival antes e após antibioticoterapia. Preconizou-se antibioticoterapia distinta em dois grupos, com 10 animais cada: clindamicina (G1) e metronidazol + espiramicina (G2). Observou-se crescimento bacteriano subgengival na maioria dos cães com DP e correlação entre a severidade da DP e a idade dos animais. Houve redução significativa no crescimento bacteriano após a antibioticoterapia e o antibiograma demonstrou maior sensibilidade à clindamicina, seguido da espiramicina; todos os microrganismos foram resistentes ao metronidazol. ___________________________________________________________________________________________________ ABSTRACTThe objective was to determine microbiote of the subgingival bacterial plaque of dogs with periodontal disease (PD) and establish the effect of antibioticotherapy on its reduction. Twenty dogs with varied stages of PD were evaluated and samples of their subgingival bacterial plaque were collected. Distinct antibiotic protocols were used in two groups with ten animals each: clindamycin (G1) and metronidazole + espiramycin (G2). New subgingival samples were collected 15 days after antibiotic therapy started. There were observed subgingival bacterial culture on most dogs with PD and correlation between severity of PD and age. There was reduction of bacterial growth in 20% of the samples after treatment and antibiogram showed higher sensibility to clindamycin, followed by espiramycin - all microorganisms were resistant to metronidazole.