Candida auris: Transmission, Risk, Diagnosis, Treatment

A patient who has spent weeks in intensive care, with a central line and several courses of antibiotics behind them, develops a bloodstream infection. The yeast that grows is resistant to the usual antifungal, and the same organism is soon found on the skin of two other patients on the ward. This is Candida auris, a yeast that colonizes skin, survives on surfaces, and moves between patients in a way ordinary Candida does not. Recognizing it quickly is as much an infection-control emergency as a treatment decision.

Candida auris (C. auris) causes a serious and sometimes fatal fungal infection that is emerging worldwide. First identified in 2009 in Japan, this drug-resistant yeast has now been reported in more than 40 countries across six continents. It is a particular threat to vulnerable patients, especially those who are hospitalized or critically ill. The World Health Organization lists C. auris as a critical-priority fungal pathogen, its highest category of concern.

The reported numbers may understate the true spread, because identifying C. auris requires specialized laboratory methods that many labs do not have. Whole-genome sequencing shows that C. auris emerged as several distinct genetic groups (clades) in different regions of the world at roughly the same time, which is unusual and still not fully explained.

Why Candida auris matters

Three features make C. auris a serious public-health concern, and together they explain why it is treated as an infection-control emergency.

1. It is often drug-resistant. Most isolates are resistant to the azoles (such as fluconazole), a substantial share are resistant to amphotericin B, and a smaller but rising number are resistant to the echinocandins, the first-line drugs. Some isolates are resistant to all three classes (pan-resistant), which leaves very few treatment options.
2. It spreads in healthcare settings. Unlike most Candida, C. auris colonizes the skin and survives for long periods on surfaces and equipment. It moves from patient to patient in hospitals and long-term care facilities, and some common disinfectants do not reliably kill it. This is why a single case triggers a containment response.
3. It is easily misidentified. Standard laboratory methods often mistake C. auris for other yeasts, which delays both correct treatment and infection-control measures. Reliable identification usually requires MALDI-TOF mass spectrometry or molecular methods.

Transmission

C. auris spreads mainly in healthcare settings, in three linked ways. First, it colonizes the skin of patients, often without causing any symptoms. A colonized patient carries the organism on their skin and can pass it on without being sick themselves. Second, it contaminates the environment. C. auris survives for weeks on bed rails, equipment, and other surfaces, and resists some routine disinfectants, so it persists in the patient's surroundings. Third, it transfers by contact, from patient to patient on the hands of healthcare workers, on shared equipment, and through the contaminated environment.

Colonization is the key to understanding its spread. Skin colonization is silent, so the organism moves through a ward before anyone is obviously infected. This is why control depends on screening at-risk patients on admission, isolating those who are colonized or infected, strict hand hygiene, and thorough cleaning with disinfectants proven to work against C. auris.

It is not spread through casual community contact in the way respiratory viruses are. The risk is concentrated in hospitals and long-term care facilities, among patients with serious underlying illness.

People at risk

Patients who have been hospitalized in a healthcare facility a long time, have a central venous catheter, or other lines or tubes entering their body, or have previously received antibiotics or antifungal medications, appear to be at the highest risk of infection with this yeast.

Candida auris vs Candida albicans

You may be confused C. auris with the familiar Candida albicans. They are both Candida yeasts, but they behave very differently, and the differences are exactly what make C. auris dangerous.

The practical message: C. albicans is mainly a problem for the individual patient, while C. auris is also a problem for the whole ward. For the general biology of Candida and how C. albicans is identified, see the main article on Candida albicans.

Infections caused by C. auris

• Blood stream infection (in some patients it can spread throughout the body causing serious invasive infections).
• Wound infection
• Ear infection

C. auris got its name because it was isolated from a patient with an ear infection in Japan. Auris is the Latin word for ear.

More than 1 in 3 patients with invasive C. auris infection (for example, an infection that affects the blood, heart, or brain) die. It also has been isolated from respiratory and urine specimens, but it is unclear if it causes infections in the lung or bladder.

Laboratory Diagnosis

Sample: Blood or other body fluids

Candida auris under the microscope

C. auris looks like a fairly ordinary yeast. It appears as oval budding yeast cells and, like other Candida, stains Gram-positive on a Gram stain. It usually does not form true hyphae, and unlike Candida albicans it is germ-tube negative.

The important point is that microscopy alone cannot identify C. auris or distinguish it from other Candida species. Its appearance is not distinctive enough, which is exactly why it is so often misidentified and why species-level identification depends on MALDI-TOF mass spectrometry or molecular methods.

Culture

Figure: Candida auris colonies

Culture grows the organism, but telling C. auris apart from other yeasts, particularly Candida haemulonii, is difficult. C. auris is frequently misidentified as other Candida species and related yeasts by traditional phenotypic identification systems such as VITEK 2 YST, API 20C, BD Phoenix, and MicroScan. Because of this, any yeast that cannot be confidently identified, or that is reported as Candida haemulonii or another uncommon species from an at-risk patient, should raise suspicion for C. auris and be sent for confirmatory testing.

MALDI-TOF

Special laboratory tests are needed to identify C. auris. Diagnostic devices based on matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) can differentiate C. auris from other Candida species.

Treatment

For invasive C. auris infection, an echinocandin is the recommended first-line treatment, started before susceptibility results are available. Treatment is guided by susceptibility testing once it is available, because resistance is common. Some isolates are resistant to all three main antifungal classes (azoles, echinocandins, and polyenes), and these pan-resistant infections are very difficult to treat and may require combinations of antifungals under specialist guidance.

An important distinction: antifungal treatment is for patients with actual C. auris infection, not for patients who are only colonized. Colonized patients are managed with infection-control measures, not antifungal drugs. This article gives class-level guidance only; regimens are decided by the treating clinician.

How to Remember

Auris means ear. C. auris was first isolated from an ear infection in Japan; "auris" is Latin for ear.

A ward problem, not just a patient problem. Unlike ordinary Candida, C. auris colonizes skin, survives on surfaces, and spreads between patients, so it is an infection-control emergency.

Silent skin colonization drives spread. Patients carry it on their skin without symptoms, which is why it moves through a ward before anyone looks sick.

Echinocandin first, but check susceptibility. Echinocandins are first-line for infection, but resistance is common, so susceptibility testing guides therapy. Treat infection, not colonization.

Easily missed. Routine lab methods misidentify it. MALDI-TOF or molecular methods are needed.

Key exam facts

Where Students Get Confused

"Candida auris is just another Candida albicans." No. Both are Candida yeasts, but C. auris is often multidrug-resistant, colonizes skin, survives on surfaces, and spreads between patients. C. albicans rarely does these things.

"You treat colonized patients with antifungals." No. Antifungals are for actual infection. Colonized patients (carrying the organism without infection) are managed with infection-control measures.

"A negative germ tube rules out Candida." No. It helps rule out C. albicans, which is germ-tube positive. C. auris is germ-tube negative, so a negative result in the right setting should prompt further identification.

"Microscopy can identify Candida auris." No. It looks like an ordinary budding yeast and stains Gram-positive. It cannot be identified by appearance, which is why MALDI-TOF or molecular methods are needed.

"Candida auris is spread in the community like a cold." No. It spreads mainly in hospitals and long-term care facilities, among patients with serious underlying illness, through skin colonization, contaminated surfaces, and contact.

References and further readings

• Centers for Disease Control and Prevention. Candida auris information for healthcare professionals. https://www.cdc.gov/candida-auris/
• World Health Organization. (2022). WHO fungal priority pathogens list. https://www.who.int/publications/i/item/9789240060241
• Sanyaolu, A., et al. (2025). Candida auris: a continuing threat. (Review; see PubMed Central.)