The Dangerous Interaction Between Salmonella and Yeast in the Gut

Recent research led by the University of Illinois Chicago has revealed a complex and potentially harmful relationship between the common gut yeast, Candida albicans, and the bacterial pathogen Salmonella Typhimurium. The study demonstrates that C. albicans, which is present in over 60% of healthy individuals as a normal component of the gut microbiome, can facilitate the establishment and spread of Salmonella within the host. When Salmonella interacts with the yeast, a specific Salmonella protein named SopB triggers the yeast to release arginine, a metabolite that activates Salmonella's invasion mechanisms and suppresses the host’s inflammatory response.

This cross-kingdom interaction enhances the pathogen’s ability to invade intestinal tissues and disseminate to other organs such as the spleen and liver. The study employed various models, including mouse strains and human cell lines, to explore these mechanisms. They found that the presence of C. albicans increases bacterial loads in the gut and systemically, leading to greater weight loss and more severe infections.

Mechanistically, Candida's arginine production, driven by SopB, plays a central role. When Candida produces arginine, it significantly boosts Salmonella’s invasion capability in a dose-dependent manner. Mutations that impair arginine synthesis in Candida or Salmonella’s arginine transporters diminish this effect, highlighting the importance of arginine as a key metabolite connecting the yeast, bacteria, and host immune responses.

Additionally, co-infected mice exhibited reduced levels of inflammatory markers such as IL-17, CXCL1, and IFN-γ, indicating that Candida’s modulation of inflammation favors bacterial colonization and spread. Supplementing drinking water with L-arginine mimicked these effects by increasing organ dissemination, whereas L-lysine partially reversed them.

The findings suggest that colonization by C. albicans can be a significant risk factor for Salmonella infections, especially in immunocompromised individuals. The study proposes that antifungal strategies might reduce susceptibility to bacterial pathogens. Overall, the research reveals a novel pathogenic partnership in the gut, emphasizing the critical role of gut fungi and their metabolites in bacterial infections and host immune regulation.

This research paper titled "Commensal yeast promotes Salmonella Typhimurium virulence" was published in Nature and provides new insights into how gut fungi influence bacterial pathogenicity and systemic infections.

source: https://medicalxpress.com/news/2025-09-pathological-partnership-salmonella-yeast-gut.html