A common gum disease bug, Porphyromonas gingivalis (Pg) plays a 'central role' in the development of Alzheimer's Disease (AD), according to scientists who say they have finally found 'solid evidence' linking the bacteria to dementia (http://advances.sciencemag.org/content/5/1/eaau3333).

There have been previous suggestions that Pg may play a role in Alzheimer's, but the latest study by a US-led international team of scientists appears to put the link beyond question.

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Researchers made the discovery after analysing brain tissue, spinal fluid, and saliva from dead and living patients with diagnosed and suspected Alzheimer's. They found evidence of toxic enzymes, known as gingipains,that are released by P. gingivalis, as well as DNA from the bacterium.

The scientists tested drugs that blocked gingipains and found they were able halt the neurodegeneration. The team has now developed a new drug, COR388, that better penetrates the central nervous system and could form the basis of a human Alzheimer's treatment.

A large-scale clinical trial that will involve giving the drug to patients with mild to moderate Alzheimer's is planned for later this year. Professor Damien Walmsley, scientific adviser to the BDA, said: 'This study offers a welcome reminder that oral health can't remain an optional extra in our health service. Everyone's life can be improved by regular appointments and good oral hygiene.'