Deadly Candida auris hides in hair follicles by rewiring skin immunity

Since its discovery in 2009, Candida auris, a dangerous fungus, has spread across hospitals globally. This pathogen can remain undetected on the skin, but it poses a deadly threat when it infiltrates the bloodstream, causing approximately 3,000 annual deaths in U.S. hospitals and long-term care facilities. To uncover how C. auris differs from other skin fungi like Candida albicans, researchers compared the two in mice.

While C. albicans is swiftly cleared by the immune system, C. auris persists, hiding in hair follicles. Professor Dean Merrill of UCSF explained that C. auris outperforms other fungi in colonizing skin, positioning itself for potential invasion when the immune system weakens. The study found that C. albicans stimulates an immune signal called IL-17, which rejuvenates the skin's surface and enhances antifungal defenses, eliminating the infection.

Conversely, C. auris triggers interferon gamma, a signal typically associated with viral infections. It achieves this by altering its outer cell wall to expose more chitin, a molecule that prompts immune cells to release interferon gamma around hair follicles. This interferon gamma weakens the skin's antifungal defenses, including IL-17, and decelerates the natural replacement of hair follicle cells, leading to an accumulation of damaged cells—a perfect environment for C. auris growth.

The researchers suggest potential strategies to prevent C. auris persistence, such as drugs that redirect the immune system towards IL-17 rather than interferon gamma or drugs that block chitin. These findings provide insights into how microbes can coexist without causing harm until they invade deeper tissues in vulnerable patients, potentially explaining the pathogen's ability to cause severe infections.