A new study reveals that a common yeast in the human gut can make salmonella infections more severe. Researchers at the University of Illinois Chicago found that candida albicans, a fungus present in more than half of healthy people, interacts with salmonella bacteria in ways that help the infection spread.
Published in Nature, the research shows that salmonella binds to candida in the gut and sets off a chain reaction. Together, the two microbes boost levels of arginine, an amino acid. This not only enhances salmonella’s ability to invade intestinal cells but also dampens the body’s immune response, allowing the infection to reach organs like the liver and spleen.
“When we started this project, we just wanted to learn more about what the role of the fungal gut microbiota is during infection,” said Judith Behnsen, Ph.D., associate professor of microbiology and immunology at UIC and senior author of the study. “We learned that candida albicans was blooming in these mice.”
In experiments, mice that carried both candida and salmonella were sicker than those infected with salmonella alone. The combination made it easier for the bacteria to multiply and spread.
Though candida doesn’t usually pose a risk to healthy people, the findings suggest it could influence how doctors approach treatment for vulnerable groups, such as children, older adults, or those with weakened immune systems. Standard antibiotic treatment for salmonella infections doesn’t affect candida, which means fungal blooms could complicate recovery.
The researchers say these results highlight the importance of looking at the gut microbiome not just as bacteria, but as a mix of bacteria, fungi, and other organisms that interact in surprising ways.
This work was supported by grants from the U.S. National Institutes of Health to J.B. and to B.M.P., as well as startup funds from the Department of Microbiology and Immunology at the University of Illinois Chicago. Additional support came from NIH training, core facilities and collaborative resources at UIC and the PennCHOP Microbiome Program.