Poor oral health can play a role in onset of Alzheimer's disease, say researchers who found evidence of the link between bacteria in a common type of gum disease and people with dementia.

The study, published in the journal Science Advances, identified Porphyromonas gingivalis -- the keystone pathogen in chronic periodontitis -- in the brain of Alzheimer's disease patients. Toxic proteases from the bacterium called gingipains were also identified in the brain of Alzheimer's patients, and levels correlated with tau and ubiquitin pathology. 

The findings offer hope for a new way of tackling the illness, for which there is no cure and no effective treatments, the BBC reported. Tests on mice confirmed the bacteria could travel from the mouth to the brain and showed the toxic protein they secrete, called gingipain, which destroyed brain neurons.

The bacteria also increased production of amyloid beta, a component of the amyloid plaques commonly associated with Alzheimer's. Following this, scientists Stephen Dominy from founders of the pharmaceutical firm Cortexyme, tested drugs in mice aimed at blocking the toxic proteins and found they were able to halt degeneration in the brain.

The same bacteria was further found in 51 out of 53 brain autopsies of Alzheimer's disease patients. The team has now developed a new drug they hope could form the basis of a human treatment and plan to test it in people with mild to moderate Alzheimer's, in a clinical trial later in 2019.