Candida Auris is a type of yeast that has not received much attention, but that could change. Its initial outbreak began in 2009 when a Japanese woman in her 70s was admitted to a hospital in Tokyo with an ear infection. The doctors collected a sample of the discharge from her ear to identify the cause of the infection. It was discovered that the woman's ear infection was caused by a unique type of yeast, called Candida Auris. While baker's yeast is commonly used to make beer and bread, Candida Auris is a type of yeast that can cause serious, persistent infections that are difficult to treat with standard antibiotics.
It is a dangerous fungus that poses a significant threat to global health. The Centers for Disease Control and Prevention (CDC) is apprehensive about Candida Auris for three primary bases: it is often resistant to multiple antifungal drugs, it is difficult to accurately identify with standard laboratory methods, and it has caused outbreaks in healthcare settings. C. Auris can be misidentified in labs without specialized technology, leading to inappropriate treatment. It is important to identify C. Auris quickly in hospitalized patients to prevent its spread and take necessary precautions.
Triggering Possible Global Outbreak
Candida Auris was found to be unusually resistant to stress and has spread to every continent since it was first identified in 2009. It is typically found in hospitals and affects individuals who are already weakened. For example, in 2015, the Royal Brompton Hospital in London struggled to control an outbreak of Candida Auris and attempted to eradicate the infection through a week-long spraying campaign using hydrogen peroxide.
The yeast is often resistant to multiple antifungal drugs and can be difficult to identify with standard laboratory methods. To test whether any microorganisms had survived the spraying campaign at the Royal Brompton Hospital in London, a gel-coated plate was placed in the middle of the room.
Any microorganisms that were able to withstand the spray would be drawn to the gel, revealing their presence. Only a single organism occurred on the gelling vessel. In 2022, a Danish patient who had been treated in a South African hospital was found to have Candida Auris on their skin upon returning home and being admitted to a Danish hospital. The patient had several wounds that needed treatment.
The issue with this new yeast fungus is that it is resistant to medicine and is difficult to kill.
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Lethal Yeast Fungus
The presence of Candida Auris on the skin is not inherently dangerous, but it can become a concern if it enters the bloodstream. To prevent the spread of the fungus to other patients, the Danish hospital took extra precautions with the patient who had been treated in South Africa. The patient was admitted to two isolated rooms, and staff had to go through two locks to access them. The patient recovered and was discharged, and the rooms and locks were thoroughly disinfected.
However, the next patient who was admitted to one of these rooms became infected with Candida Auris in the bloodstream after just five hours. Maiken Cavling Arendrup, head of the Unit for Mycology at the Statens Serum Institut in Denmark, who has studied the cases, found it difficult to understand how the infection occurred.
Four cases of Candida Auris have been recorded in Denmark so far, all in 2022. Three cases involved people with the fungus on their skin after returning from abroad, while the fourth patient became infected in the blood after spending just five hours in a hospital room. All four patients have recovered. Maria Szomek from the Department of Biochemistry and Molecular Biology explained that Candida Auris is difficult to kill because it is multi-resistant and can cause serious infections that are difficult to treat.
Developing New Polyene-Based Drugs
While there are many antifungal medications available to combat Candida Auris, they are becoming less effective as the yeast is very good at developing resistance. The current challenge is to develop better medications that can inhibit growth and kill any remaining yeast cells. Existing antifungal medications for Candida Auris and other yeasts are often based on polyenes, which are naturally occurring substances produced by certain bacteria as part of their defense system.
However, the mechanisms by which polyenes kill yeast cells are not fully understood. To improve polyene-based drugs and better understand how they work, the research group led by Daniel Wüstner at the Department of Biochemistry and Molecular Biology is using advanced microscopy to study what happens to yeast cells when they are attacked by polyenes. The group is also collaborating with colleagues in theoretical and computational chemistry at Leipzig University and Humboldt University Berlin.
The researchers are not working with real Candida Auris cells, but rather with harmless models that they expose to polyenes from the fungicide Natamycin. They are interested in understanding how the polyenes can penetrate the cell membrane and bind to and interact with ergosterol, a subgroup of steroids that is the target of the polyenes' attack. Szomek explained that this knowledge is essential for developing new and improved polyene-based drugs.
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