In the infected ear of a 70-year-old Japanese woman, an unknown fungus called Candida auris was discovered in 2009. It was not clear where C. auris suddenly came from, but soon afterwards different strains appear all over the world. It turns out to be a stubborn fungus that is not easy to clean up, which moreover is usually resistant to fungicides, the so-called fungicides.
Last year, the New York Times ran an alarming article on the growing problem. The authors cite the example of a man infected with C. auris who dies in Mount Sinai hospital after 90 days. The fungus, meanwhile, had settled in the mattress, the curtains, the walls, the telephone; basically anywhere in the hospital room, could only be removed with a lot of effort. Only after special cleaning and removal of part of the ceiling and the tiled floor did the hospital get the mold underneath.
“We started researching C. auris with international colleagues because almost nothing was known about this fungus,” says Mariolina Bruno, of the Department of Internal Medicine at Radboudumc. The research results have now been published in Nature Microbiology. The research shows that the fungus is especially dangerous for people with a reduced immune system. Bruno: “A well-functioning immune system recognizes the fungus very well and can then also clean up the fungus well.”
Careful study of the human immune response to Cauris infection revealed that certain components of the fungal cell wall play an essential role in this recognition. David Williams, East Tennessee State University: “These are unique structures that you will not find in other fungi. These specific chemical structures stimulate the immune system sufficiently to take action and to clear the fungus. ”
Resistant to fungicides
The fact that C. auris is considered a serious emerging infectious disease is mainly due to the fact that it is resistant to many disinfectants and fungicides. People with an invasive C. auris fungal infection have a 30 to 60 percent chance of dying from it. Precisely because the fungus is insensitive to many fungicides. Alistair Brown, University of Exeter: “Our research not only shows that these cell wall components are important for recognition by the immune system, but also that they are indispensable for the fungus. Medicines that selectively block the production and action of these components are currently being investigated for safety and effectiveness. This may include the ideal candidate to tackle the fungus. ”
Because these cell wall components are indispensable for C. auris, the chance of resistance to such a new drug is small. To develop resistance, the fungus must at least stay alive, so that it can adapt step by step to the new drug.
Diagnosis and monitoring
Candida auris is a family of the much more famous fungi Candida albicans, which can cause vaginal fungus in women. In the study C. albicans therefore served as comparison material. Bruno: “On the one hand we see that C auris elicits a better immune response than C. albicans. On the other hand, C. auris appears to be less pathogenic. But once in the bloodstream, both fungi are usually life-threatening. ”
Another contributing factor to the problem is that C auris is not so easy to identify. As a result, it is easily confused with other fungi, which can delay treatment. Jacques Meis, medical microbiologist at the CWZ: “You actually have to characterize fungi molecularly so that it is immediately clear which fungus you are dealing with, but not every laboratory has the facilities for this.” Earlier this year, he and Paul Verweij (Radboudumc) argued for nationwide monitoring of serious fungal infections in order to gain a better insight into the burden of disease and mortality rates.
The question why C auris suddenly pops up in 2009 has still not been answered. The fungus was also not found in stored patient material from previous years, making it indeed appear to be a new or altered fungus. Perhaps it is global warming, suggests the American microbiologist Arturo Casadevall in TIME. Most fungi thrive at relatively low temperatures, but due to an increase in the average temperature, it is conceivable that a fungus will break through its thermal restriction and thus suddenly colonize the human body.
“An interesting point of view,” says Bruno, “but without further proof it is still very speculative. Apart from the actual genesis or ‘birth’ of C. auris, the article in Nature Microbiology provides information about how the interaction between humans and the fungus C. auris proceeds: how the fungus stimulates the immune system, where the pharmacological Achilles heel of C. auris can be found and where there are opportunities for possible immunotherapy. ”