Effect of spiramycin and metronidazole on canine dental biofilm bacteria

Periodontal diseases are the most common condition in companion animal practice. The administration of antibiotics is associated with the therapy of these diseases. The aim of the present study was to verify the effect of antibiotics on canine dental biofilm bacteria due to increasing antibiotic resistance. Dental biofilm samples were taken from six dogs before and after administration of antibiotics, specifically, the combination of spiramycin and metronidazole. The samples were cultured on solid media under aerobic and anaerobic conditions. Sequencing analysis of the 16S rRNA gene was used to identify bacterial isolates. In addition, total bacterial DNA was extracted from samples from one dog and the V3−V4 region of the 16S rRNA gene was sequenced using the Illumina MiSeq platform. Using cultivation, 55 isolates belonging to 4 phyla were isolated before antibiotics administration, and 36 isolates belonging to 3 phyla were isolated after antibiotics administration. A significant decrease was noted in the genera Porphyromonas, Neisseria and Frederiksenia, whereas there was a significant increase in the genus Streptococcus. Of the total microbiota, there were 69 operational taxonomic units (OTUs) belonging to 11 phyla before antibiotics administration, and 51 OTUs belonging to 8 phyla after antibiotics administration. A significant decrease was recorded in the genus Porphyromonas, while a significant increase in the genus Capnocytophaga. The significant effect of spiramycin and metronidazole on the genus Porphyromonas at the time of their administration was confirmed by both cultivation and amplicon sequencing.