Pathogen with adhesive power

In 2009, a previously unknown yeast fungus was discovered in Japan that had colonised the ear canal of a 70-year-old female patient. It was named Candida auris (lat. auris = ear) after the place where it was found. The fungus, which can also affect other parts of the body, has since spread worldwide. The US Department of Health and Human Services (DHHS) has labelled the spread of the pathogen as alarming for various reasons: the fungus is multiresistant, it spreads easily from person to person and it can cause serious infections that are often fatal.

From 2013 to 2021, there were around 1800 reported Candida auris infections in Europe, most of them in Spain, Italy and the UK. In the majority of patients, the fungal colonisations were harmless, but a quarter suffered blood poisoning or other serious infections. In Germany, fewer than 50 cases of Candida auris have been reported to date. The patients had brought the fungus with them from travelling to risk areas; in only one case had the fungus been transmitted from person to person in hospital.

Candida auris colonises the skin and mucous membranes, including the ears, hands, nose, armpits, groin, throat and wounds as well as the intestines, respiratory tract and urinary tract. Infection poses a particular risk to immunocompromised patients, those with serious preexisting conditions or chronic illnesses. Even if the number of cases has so far been limited, experts consider the spread to be worrying. This is because if the fungus enters the bloodstream, the infection is fatal in 30 to 60 per cent of cases. Only a few antimycotics are available for treatment. The resistance rate to fluconazole is already over 80 per cent. Also, the infection often no longer responds to the echinocandins drug class. Such multiresistance, which is common in bacteria, is rather unusual in fungi. Experts therefore advise increased vigilance, but also emphasise that the fungus poses no danger to healthy people.

In addition to the development of multiresistance, the yeast fungus has another special feature: while other Candida diseases are endogenous infections in which the pathogen originates from the body’s own flora, Candida auris is transmitted from person to person via smear infection. The fungus can remain on the skin for a long time without causing symptoms and can then be passed on unnoticed. Contaminated surfaces of medical devices such as catheters or prostheses also pose a risk, as the fungus can survive on them for more than two weeks. This explains why many of the infections have occurred in hospitals, i.e. nosocomially.

The largest outbreak to date occurred in a London hospital, where 50 patients became infected within 16 months. However, an infection in Germany is very unlikely. Last year, Dr. Alexander Maximilian Aldejohann, a specialist in microbiology, virology and infection epidemiology at the Institute of Hygiene and Microbiology at the University of Würzburg, was quoted in a press release from the institute as saying that patients in Germany need not be afraid of becoming infected in hospital. The risk of infection is also low in the private sphere. This would require very close physical contact. Transmission between clothed persons is rather low. Infection via the air, as with cold viruses, also appears to be ruled out.

As Candida auris is generally rare in Germany, experts in this country do not recommend any specific prophylactic measures for medical and care facilities in addition to the usual hygiene measures. Patients infected with Candida auris should be isolated. As there are indications of increased resistance to disinfectants, especially quaternary ammonium compounds, the room should be disinfected with a levurocidal agent against fungal spores, for example based on H₂O₂, after a patient has been discharged. In order to keep an eye on the development of Candida auris infections, it has been mandatory to report the detection of Candida auris in primarily sterile samples such as blood in Germany since 2023. This is the first mandatory reporting of a fungal infection in Germany. However, it does not apply to detection in swabs from the nose, throat, skin or wounds.

Researchers at the University of Michigan have recently discovered how Candida auris manages to adhere so successfully to surfaces: The fungus has a previously unknown adhesion protein that forms so called cationbonds. Similar adhesion principles are known from mussels and barnacles. This adhesion protein appears to be decisive for the dangerousness of Candida auris. Mutants without the special adhesion protein were significantly less harmful. The findings could lead to approaches for new therapies. Everyone can also help to minimise the risk of a fungal infection by leading a healthy lifestyle and adhering to hygiene standards. As Candida fungi preferentially infect immunocompromised people, for example in the case of a severe respiratory infection, the recommended vaccinations against influenza and Covid 19 also indirectly protect against mycosis.

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