Longitudinal Analysis of Canine Oral Microbiome Using Whole Genome Sequencing in Aging Companion Dogs

Simple Summary The prevalence of dental disease and cognitive decline in elderly dogs is extremely high, and, given the known relationship between dental disease and Alzheimer's Disease in people, this study sought to describe the changes in oral microbiota in aged pet dogs over time. By sequencing oral swabs, we were able to identify bacterial and fungal populations in the dogs' mouths. The most common bacterial species present, Phorphorymonas spp. is known to produce factors that cause neurodegeneration. Moreover, Leptotrichia, another bacterial species present, correlated to cognition scores in these dogs. We conclude that this small exploratory study shows the importance of defining the oral microbiota in aged dogs with a view to understanding potential therapeutic targets. Larger prospective studies should be undertaken as a priority.Abstract Aged companion dogs have a high prevalence of periodontal disease and canine cognitive dysfunction syndrome (CCDS) and the two disorders are correlated. Similarly, periodontal disease and Alzheimer's Disease are correlated in people. However, little is known about the oral microbiota of aging dogs. The goal of this project was to characterize the longitudinal changes in oral microbiota in aged dogs. Oral swabs were taken from ten senior client-owned dogs on 2-3 occasions spanning 24 months and they underwent whole genome shotgun (WGS) sequencing. Cognitive status was established at each sampling time. A statistically significant increase in alpha diversity for bacterial and fungal species was observed between the first and last study visits. Bacteroidetes and proteobacteria were the most abundant bacterial phyla. Porphyromonas gulae was the most abundant bacterial species (11.6% of total reads). The species Lactobacillus gasseri had a statistically significant increase in relative abundance with age whereas Leptotrichia sp. oral taxon 212 had a statistically significant positive longitudinal association with cognition score. There is an increased fungal and bacterial alpha diversity in aging dogs over time and nearly universal oral dysbiosis. The role of the oral microbiota, particularly Leptotrichia and P. gulae and P. gingivalis, in aging and CCDS warrants further investigation.