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J Alzheimers Dis. 2019 Oct 3. doi: 10.3233/JAD-190587. [Epub ahead of print]

Analysis of Salivary Microbiome in Patients with Alzheimer's Disease.

Liu XX1,2, Jiao B1,2,3, Liao XX2,4, Guo LN1,2, Yuan ZH1,2, Wang X1,2, Xiao XW1,2, Zhang XY1,2, Tang BS1,2,3,5,6,7, Shen L1,2,3,8.

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Department of Neurology, Xiangya Hospital, Central South University, Changsha, China.
National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, China.
Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, China.
Department of Geriatrics Neurology, Xiangya Hospital, Central South University, Changsha, China.
Parkinson's Disease Center of Beijing Institute for Brain Disorders, Beijing, China.
Collaborative Innovation Center for Brain Science, Shanghai, China.
Collaborative Innovation Center for Genetics and Development, Shanghai, China.
Key Laboratory of Organ Injury, Aging and Regenerative Medicine of Hunan Province, Changsha, China.


Recent studies found that poor oral hygiene was associated with increased risk of dementia, and the number of oral bacteria significantly increased in the brain tissues of patients with Alzheimer's disease (AD), suggesting that the oral microbiota may play an important role in the pathogenesis of AD. However, the actual composition of oral bacteria communities in patients with AD and whether these oral bacteria are associated with disease severity remain largely unknown. Also, the APOEɛ4 polymorphism is a strong risk factor for sporadic AD, and it would be pertinent to see if the bacterial flora was different in those patients who were APOEɛ4 positive. A total of 78 subjects were recruited in this study, including 39 patients with AD and 39 healthy controls. Saliva was collected from each subject. 16S ribosomal RNA (16S rRNA) sequencing was conducted to analyze the salivary microbiota, and Sanger sequencing was performed to analyze the APOE genotype. There was a significantly lower richness and diversity of saliva microbiota detected in AD patients than healthy controls. The relative abundance of Moraxella, Leptotrichia, and Sphaerochaeta in the saliva of AD patients greatly increased, whereas that of Rothia was significantly reduced. Compared with APOEɛ4 (-) patients, the level of Abiotrophia and Desulfomicrobium was comparatively abundant, while Actinobacillus and Actinomyces decreased significantly in patients carrying the APOEɛ4. No bacteria were found to be associated with the severity of AD. This is the first study to analyze the salivary microorganisms in patients with AD, and we discovered that the composition of salivary microbiome was altered in AD, providing further support for the role of the oral microbiome in AD development.


16S rRNA; APOE; Alzheimer’s disease; oral microbiome


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