In 2009, a yeast was extracted from the ear canal of a hospitalized Japanese patient, resulting in the discovery a novel Candida species never before seen. Over time, Candida auris, as it was named, became notorious for having potential resistance to all 3 classes of antifungal drugs (polyenes, azoles and even the newer echinocandins), making it especially challenging to manage. During the course of the next 7 years, this organism moved westward, from Japan to Southeast Asia, the Middle East, Europe and Africa, before crossing overseas and making it’s way to Venezuela. Now, the CDC has reported that this organism has been isolated in 7 patients here in the United States (see link here).

Candida are budding yeasts that exist as part of the normal human flora. They colonize the skin, the GI tract, and even the upper airways. They are the cause of diaper rashes in babies, and yeast infections in women. In these cases, infection occurs due to changes in the microbiome of the skin or genitourinary tract, allowing for the fungus to overgrow and cause pathogenic disease. They are burdensome infections, but in the majority of cases they were not considered life threatening.

In the age of modern medicine however, new risk factors have emerged that have made Candida more invasive in nature, and in turn more deadly. With the development of immunosuppressive drugs, the advent of organ and bone marrow transplantation, and the use of total parenteral nutrition, Candida species have found ways to become more invasive in nature, wreaking havoc on the human body and causing a variety of clinical manifestations that are potentially life threatening.

To begin addressing the rising rates of invasive Candida infections noted in hospitals, aggressive attempts have been made in finding novel drugs and drug-classes to fight off these infections more effectively. However, despite extensive efforts by researchers and pharmaceutical companies alike, there are currently only 3 significant classes of antifungal drugs available. The polyenes, which are the oldest class of drugs, include drugs such as amphotericin B, which tend to be quite toxic to the liver and kidneys if used for prolonged periods of time. Azole drugs, which are the broadest category of antifungals, are somewhat less toxic, and are currently being used to manage infections ranging from Candida, to rare endemic infections such as Histoplasma, Blastomyces, Cryptococcus, Aspergillus and Mucorales species. Lastly, the echinocandins are considered to be the least toxic class of antifungals, however they cover only a limited range of fungal organisms, namely Candida and Aspergillus species. Unlike antibiotics, where multiple drug classes and options exist, with antifungals, only a limited number of treatment options are available.

In the setting of these limited options, hospitals in the U.S. have been seeing an increasing number of drug-resistant Candida species appearing over time. Infections from Candida albicans, the most common pathogenic Candida species and one of the most drug susceptible, are slowly being replaced by infections occurring from Candida glabrata, Candida parapsilosis and Candida kruseii, which all tend to be more drug resistant, and allow clinicians fewer effective treatment options. The incidence of these more resistant species, amidst the presence of the above mentioned risk factors brought on by the advances of modern medicine, has created a unique situation where doctors have limited options in treating very serious and potentially life threatening infections.

If other species of drug-resistant Candida already exist, then why should we be concerned for Candida auris specifically? For one, this organism has the potential to be resistant to all 3 classes of antifungal drug classes that physicians have available, something which none of the above species possess. In addition, while the above Candida species generally existed with the human body (patient’s would develop ‘auto-infections’ or acquire infection via translocation from a normally colonized site to a sterile site), C. auris appears to be spreading within hospitals, raising concerns for potential outbreaks of infection with this organism. C. auris also appears to be targeting individuals with impaired or weakened immune systems, based on the CDC’s analysis of the 7 reported cases here, which further increases this organism’s potential for creating serious, life threatening disease. In addition, C. auris has been difficult to identify using standard culture techniques, although ‘matrix-assisted laser desorption/ionization time-of-light’ analysis (known also as MALDI-TOF) has been able to pinpoint the species fairly accurately. However, not all hospitals have such diagnostic capabilities, and this may result in under-reporting of this organism across the country, at least for the time being.

For now, the CDC is working to track this organism as carefully as possible. Limited treatment options are available, and the new 2016 guidelines on the management of invasive candidiasis (link here) do not have any specific recommendations as to how to treat C. auris if it is isolated. Ongoing research from medical mycologists and researchers will be instrumental in finding new and effective ways of treating this infection, especially if it becomes more prevalent.

In the meantime, stay tuned!

[NS]

 Links/References

Satoh, K; et al. (2009), “Candida auris sp. nov., a novel ascomycetous yeast isolated from the external ear canal of an inpatient in a Japanese hospital”, Microbiol Immunol, 53 (1): 41–44

Dall, Chris (2016-06-29), “CDC issues warning on multidrug-resistant yeast infection”, CIDRAP News.