Bacteria in the nose may increase risk of Alzheimer’s disease

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While this bacterium often causes respiratory tract infections, it has also been found in the brain which has raised the question of whether it causes damage to the central nervous system.

In a study from Griffith University and elsewhere, scientists found that a bacterium commonly present in the nose can sneak into the brain and set off a cascade of events that may lead to Alzheimer’s disease.

They discovered that the bacterium Chlamydia pneumoniae can invade the brain via the nerves of the nasal cavity.

The research team performed extensive research in animal models to show not only how the bacteria get into the brain, but also how it leads to Alzheimer’s disease pathologies.

They have previously shown that several different species of bacteria can rapidly, within 24 hours, enter the central nervous system via peripheral nerves extending between the nasal cavity and the brain.

The new study shows that once the bacteria are in the central nervous system, the cells of the brain react within days by depositing beta-amyloid peptide, which is the hallmark plaque of Alzheimer’s disease.

After several weeks, numerous gene pathways that are known to be involved in Alzheimer’s disease are also dramatically activated.

The research also showed that when the bacteria invade the olfactory nerve, peripheral nerve cells (glial cells), become infected and these cells may be how the bacteria can persist within the nervous system.

These cells are usually important defenders against bacteria, but in this case, they become infected and can help the bacteria to spread.

Researchers have suspected for a long time that bacteria, and even viruses, can lead to neuroinflammation and contribute to the initiation of Alzheimer’s disease, however, the bacteria alone may not be enough to cause disease in someone.

Perhaps it requires the combination of genetic susceptibility plus the bacteria to lead to Alzheimer’s disease in the long term.

While the studies were conducted in mice, humans have the same nerves and can be infected by the same bacteria, so the researchers believe the results are translatable to humans.

If you care about Alzheimer’s, please read studies about antioxidants that could help reduce the risk of dementia, and 5 steps to protect against Alzheimer’s and Dementia.

The study was conducted by Associate Professor Jenny Ekberg et al and published in Scientific Reports.

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