According to a new study published in PLoS Pathogens this month, foodborne pathogen growth in the gut may be linked to Alzheimer’s and Parkinson’s disease development. In the guts of mice, Salmonella Typhimurium produces curli amyloids in the cecum and colon of mice. This increases joint inflammation and cross-seeding interactions between bacterial amyloids and human amyloids that could trigger similar autoimmune reactions such as Alzheimer’s disease.
About 5% of patients who contract salmonellosis develop an autoimmune condition called relative arthritis. Some patients remain symptomatic for 5 years or even longer. Salmonella Typhimurium forms biofilms composed of curli, cellulose, BapA, and extracellular DNA that protects the pathogen from environmental stressors.
Curli are “highly aggregated, thin amyloid fibers.” In some in vitro conditions, the bacteria can produce curli at 37°C (98.6°F). The researchers found that Salmonella biofilms were formed in the mice intestines. The curli that were part of that biofilm are connected to poor health outcomes.
While scientists and doctors don’t know exactly how some of these autoimmune diseases, which include Alzheimer’s, Parkinson’s, and ALS begin, proteins similar to curli are associated with the development of those diseases. This study is the first to show that foodborne pathogens can make these amyloid proteins in the gut.
The foodborne pathogen growth and presence of curli does lead to autoimmune diseases such as reactive arthritis. The mice developed reactive arthritis within six week of infection.
The researchers next hope to confirm that this development also occurs in people. They state that, “As curli or curli-like amyloids are also produced by the commensal bacteria, it is possible that the unintended release of amyloids produced by the microbiota could trigger similar autoimmune reactions. Finally, our work provides conceptual evidence for the possibility of cross-seeding between bacterial amyloids like curli and human amyloids involved in amyloid-associated diseases such as Alzheimer’s Disease via the gut microbiome or infections.”
Miller AL, Pasternak JA, Medeiros NJ, Nicastro LK, Tursi SA, Hansen EG, et al. (2020) In vivo synthesis of bacterial amyloid curli contributes to joint inflammation during S. Typhimurium infection. PLoS Pathog 16(7): e1008591. https://doi.org/10.1371/journal.ppat.1008591
