Candida auris outbreak: How this deadly fungus hides in hair follicles to evade skin defences

Candida auris can hide deep inside hair follicles potentially helping it evade the skin's defences allowing to persist on the body and complicate outbreak control.

Candida auris.

A new study published in Science suggests that Candida auris or C. auris is a multidrug-resistant fungus that can colonise the skin without causing any symptoms creating a novel strategy to survive by residing inside hair follicles and modifying the immune system response to the body. This deadly fungus has been recognized as a serious public health threat since it was first reported in 2009 due to its invasive nature and resistance to most antifungal drugs.

According to healthcare professionals C. auris may grow on the skin without causing any symptoms which may allow people to be unaware of being carriers and spreaders of the fungus. However one reason remains a mystery as the deadly fungus persists on the skin for extended periods of time while other Candida species are more quickly cleared.

What did the study find?

The team of scientists compared C. auris with Candida albicans which is more readily eliminated from the skin. The researchers investigated the interaction between fungi and the immune system as well as the interaction of fungi with skin using mouse genetics, immunology, mouse models, single-cell RNA sequencing and the powerful 3D-confocal microscopy.

The results indicated that C. auris remained for a longer time and was found in greater amount on the skin of mice than C. albicans. Most importantly C. auris had excellent adhesion to human hair and a preference to colonize hair follicles. They further discovered that the fungus was able to penetrate up to 30 per cent of the intact mouse skin's hair follicles.

How does it hide in hair follicles?

The study found that C. auris appears to manipulate the skin's immune response. According to the findings C. albicans normally stimulates an IL-17-driven immune response which strengthens the skin barrier and promotes antifungal defence. But C. auris triggered a different response dominated by interferon-gamma (IFN ). This response involved immune cells gathering around hair follicles and releasing IFN . The researchers also noted that IFN acted directly on hair-follicle keratinocytes, suppressing genes and biological pathways associated with IL-17, skin-barrier function and antifungal defence. In other words an immune response that normally protects the body can help C. auris remain established.

The role of chitin

Researchers also discovered that C. auris changes its cell-wall structure when exposed to skin-like conditions increasing the amount of chitin displayed on its surface. This exposed chitin appeared to promote the type 1 immune response and increased IFN signalling. Suzanne Noble, MD, PhD, professor of microbiology at UCSF, described the finding as surprising because C. auris appears to use its chitin to create a favourable environment for itself around the hair follicle.

The findings provide a possible explanation for why C. auris can persist on skin and potentially remain available for transmission. They also identify the hair follicle and the interaction between chitin, IFN and IL-17 as potential targets for future treatments. However the findings primarily come from experimental models and further research is needed to establish how closely this mechanism reflects C. auris colonisation in humans. For now the study offers an important insight into how a drug-resistant fungus can exploit a normally protective immune pathway to establish a persistent skin niche.

Disclaimer: This article is for informational purposes only and does not replace professional medical advice, diagnosis or treatment. Always consult a qualified healthcare professional for concerns about Candida auris infection.