Salivary microbiome dysbiosis in patients with Alzheimer's disease

Background Investigating human oral microbiota is now of great interest, being clinically significant for general and oral health. Many research studies have started to focus on the link between oral microbial dysbiosis and Alzheimer's disease. However, little is known about North African populations. Objective We aimed to distinguish the dissimilarity in the structure of microbial oral flora between the Alzheimer's disease patients and healthy controls in a Tunisian population. Methods We investigated the salivary microbiota using next-generation shotgun sequencing. Results The overall structure of the oral microbial community of the Alzheimer's disease patient group was obviously different from the healthy control group. Significantly higher levels of Haemophilus (25.26%) were noticed in the AD group. However, Neisseria (10.17%) showed lower levels compared to the HC group. Considering the disease severity, Selenomonas and Aggregatibacter showed gradually higher levels as the disease progressed. Porphyromonas showed the highest levels in the mild stage of the disease, while Treponema, Selenomonas, and Peptostreptococcus were associated with severe stage. The presence of key taxa, Aggregatibacter and Selenomonas may constitute a dysbiosis signature in individuals with AD. Conclusions These findings may be of high relevance for orienting further studies on evaluating the physio-pathological process, confirming the implication of oral microbiota in AD and opening diagnostic and therapeutic avenues.