Alzheimer’s Brains Have Higher and Different Amount of Bacteria

By Craig Tanio, MD

Alzheimer’s Brains Have Higher and Different Amount of Bacteria

As researchers diligently look for the root causes of Alzheimer’s disease, one of the critical common pathways is higher inflammation and potentially infection.

A recent study in Frontiers in Aging Neuroscience provides important new evidence that bacterial infection could be contributing to Alzheimer’s disease. The researchers analyzed eight Alzheimer’s and six healthy brain samples from a brain bank, where people donate their brains after death for medical research. They used a technique called next generation sequencing (NGS) to detect specific bacterial genes. This technique allows researchers to see the different types and amounts of bacteria, similar to how we look at the microbiome in the gut.

The researchers showed 2 major findings

• Alzheimer’s brains have a “strikingly larger” bacterial load with up to 7-fold larger amounts of bacteria than normal brains
• Alzheimer’s brains have different types of bacteria than normal bacteria. Bacteria species associated skin, nasopharyngeal and oral areas such as Firmicutes and consistently Actinobacteria were found at a much higher level in Alzheimer’s brains.

In the last year, Dr. Rudy Tanzi and his team has shown compelling evidence in multiple articles that amyloid has antibacterial properties and that the production of amyloid be the brain’s response to infection. Loss of integrity of the blood-brain barrier and chronic infections may be some of the several root causes of Alzheimer’s disease. This recent study supports that the nasopharyngeal, skin, and oral areas may be important sources of those chronic infections.

What are the implications for patients? As we treat patients with early Alzheimer’s and mild cognitive decline, we believe it is critical to look for evidence of blood-brain barrier permeability and evidence of chronic infections in the nasopharyngeal and oral areas. Helping to address both of these situations is part of a comprehensive approach to brain health.