According to new research, bacteria in the nose may increase the risk of Alzheimer's disease

Schematics illustrating the process for quantifying the amount of viable infectious C. pneumoniae present in various mouse tissues.Credit: DOI: 10.1038/s41598-022-06749-9

At Griffith University, researchers have discovered how a common nostril bacteria might trigger a chain of events that could lead to Alzheimer's disease in humans.

Aside from respiratory tract infections, this bacteria has also been detected in the brain, raising whether it might induce central nervous system harm.

Researchers have used animal models extensively to demonstrate how the bacterium enters the brain and how it leads to Alzheimer's disease pathology.

An earlier study by Associate Professor Ekberg found that various bacterial species may quickly infiltrate the central nervous system through peripheral nerves stretching from the nasal cavity to the brain within 24 hours.

Using this prior information, researchers could deduce how this novel bacteria, Chlamydia pneumoniae, may similarly breach the blood-brain barrier and enter the brain.

Chlamydia pneumoniae is a kind of bacterium that causes respiratory system infections, including pneumonia (lung infection). By infecting the lining of the respiratory system, including the throat, windpipe, and lungs, the bacteria cause disease. Specific individuals may get infected with the virus and exhibit moderate or no symptoms. (source)

Alzheimer's disease signature plaque beta-amyloid peptide is deposited within a few days of bacteria entering the brain.

Several gene pathways associated with Alzheimer's disease are also significantly active after a few weeks.

Additionally, the study revealed that when bacteria infiltrate the olfactory nerve, peripheral nerve cells (glial cells) get infected, suggesting that these cells may be how germs survive inside the nervous system.

According to researchers, These cells are generally crucial defenders against bacteria, but they get infected and may encourage the bacterium to spread in this situation. While we have known for a long time that bacteria, and even viruses, may promote neuroinflammation and contribute to the onset of Alzheimer's disease, bacteria alone may not be sufficient to cause dementia in an individual. Perhaps a mix of genetic predisposition and bacteria is required to cause Alzheimer's disease in the long run.

While the tests were done on mice, since humans share the same nerves and are susceptible to germs, the researchers think the findings are applicable to Humans.

In the meanwhile, Researchers Are looking at therapeutic possibilities." They're working with the Griffith Institute for Drug Discovery to discover new medications that may aid glial cells in their fight against bacteria.


Chacko, A., Delbaz, A., Walkden, H. et al. Chlamydia pneumoniae can infect the central nervous system via the olfactory and trigeminal nerves and contributes to Alzheimer’s disease risk. Sci Rep 12, 2759 (2022).

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