Gum disease bacterium releases toxins that may cause Alzheimer's

Researchers have provided the strongest evidence to date that a bacterium involved in periodontitis contributes to the development of Alzheimer’s disease, rheumatoid arthritis and aspiration pneumonia.

P. gingivalis has been linked to AlzheimerMaxx Studio | Shutterstock

The research, which was presented yesterday at the annual meeting Experimental Biology in Orlando, Florida, showed how Porphyromonas gingivalis migrates from the oral cavity to the brain and other tissues.

Study investigator Professor Jan Potempa (University of Louisville School of Dentistry) says the findings underscore the importance of good oral hygiene in decreasing the risk of serious disease.

Older individuals and smokers are at a greater risk for infection and genetics are also suspected to play a role, although this aspect is not yet properly understood:

People with genetic risk factors that make them susceptible to rheumatoid arthritis or Alzheimer's disease should be extremely concerned with preventing gum disease.”

P. gingivalis is more common in Alzheimer’s patients

P. gingivalis generally starts to infiltrate gums during the teenage years and low levels of the bacteria are present in the gums of around one-fifth of people aged under 30. The bacterium is not usually harmful, unless it proliferates to the point that it triggers inflammation and causes redness, swelling, bleeding and erosion of the gums.

For the study, the team compared brain samples taken from deceased individuals with and without Alzheimer’s disease who had died at approximately the same age.

Potempa and colleagues report that P. gingivalis was more commonly found in the samples taken from people with Alzheimer’s disease, as evidenced by the bacterium’s DNA signature and the presence of toxic enzymes called gingipains that it exudes. They also present evidence that the bacterium is involved in rheumatoid arthritis and aspiration pneumonia.

In a mouse model, the team demonstrated that the bacterium can move from the oral cavity to the brain and that certain chemicals can interact with gingipains to block this migration. One drug that inhibits gingipains is currently being tested in phase 1 trials of Alzheimer’s disease and Pontempa says her team are also investigating other inhibitors of the enzymes P. gingivalis needs to “exert its devilish tasks.”

‘Brushing and flossing’ is key

Potempa and team think these enzymes could serve as potential targets for therapeutic interventions to combat various different diseases.

"The beauty of such approaches in comparison to antibiotics is that such interventions are aimed only at key pathogens, leaving alone good, commensal bacteria, which we need,” says Potempa, who adds that the best way to ensure P. gingivalis does not grow out of control is to maintain oral hygiene by brushing and flossing and visiting the dentist at least once a year.


The research was presented at Experimental Biology 2019 on Sunday 7 March. Read the abstract: Porphyromonas Gingivalis Infections Underline Association of Periodontitis with Systemic Diseases.

Sally Robertson

Written by

Sally Robertson

Sally first developed an interest in medical communications when she took on the role of Journal Development Editor for BioMed Central (BMC), after having graduated with a degree in biomedical science from Greenwich University.


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