Bacteria may travel from the nose to the brain and cause Alzheimer’s disease, research suggests

2022-05-03 0 By

Researchers in Australia have found that bacteria living in the nose can travel through the nasal nerve to the brain and trigger a chain of events that can lead to Alzheimer’s disease.The study adds to a growing body of evidence that Alzheimer’s disease may be initially triggered by a viral or bacterial infection.Chlamydia pneumoniae is a common bacterium that is a major cause of pneumonia, as well as a range of other respiratory illnesses.But worryingly, it can also sometimes be detected in the brain, suggesting it could lead to more insidious problems.In the new study, researchers from Griffith University and Queensland University of Technology set out to investigate how pneumococcus enters the brain and whether it causes damage once there.The team already has a glimpse of how the sinal-located bug makes its trek.”Our work has previously shown that several different species of bacteria can rapidly enter the central nervous system within 24 hours via the peripheral nerves that extend between the nasal cavity and the brain,” said Jenny Ekberg, lead author of the paper.In tests on mice, the team found that within 72 hours of entering the nasal cavity, the pneumococcus could infect the sense of smell and the trigeminal nerve, followed by the olfactory bulb, a small neural structure in the forebrain that processes smell.From there it’s a short trip to the rest of the brain.Most intriguingly, the researchers found that after the bacteria entered the central nervous system, it triggered several changes associated with Alzheimer’s disease.Within a few days, deposits of amyloid beta plaque begin to accumulate — a hallmark of the disease.A few weeks later, the team detected dysfunction in several genetic pathways linked to Alzheimer’s disease.The new findings join a growing body of work suggesting that Alzheimer’s disease is initially triggered by viral and bacterial infections.Common herpes viruses are the most consistent suspects, but an imbalance of bacteria in the mouth, especially those that cause gum disease, seems to be a predictor of Alzheimer’s.”We’ve suspected for a long time that bacteria or even viruses can cause neuroinflammation and contribute to the onset of Alzheimer’s, but bacteria alone may not be enough to cause someone’s disease,” Ekberg said.Maybe it takes a combination of genetic predisposition plus bacteria to cause Alzheimer’s in the long run.”The team says finding ways to target these bacteria could lead to whole new preventive treatments for Alzheimer’s.