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Candida auris, a Globally Emerging Multidrug Resistant Yeast Now in the Big Apple

Maria E. Aguero-Rosenfeld, MD.

In June 2016 the Centers for Disease Control and Prevention (CDC) issued an alert concerning an emerging multidrug resistant (MDR) Candida species. This organism was first described  in Japan in 2009 where it was isolated  from the external ear canal of a patient, hence the name C. auris. Since then C. auris  has caused outbreaks in institutions in several countries located on different continents. It is unclear how this organism emerged in different geographic locations almost simultaneously. Furthermore, gene sequence analysis has shown that distinct clones  predominate in every region.

Most frequently, C. auris has been cultured from blood, respiratory samples, and wound specimens particularly from hospitalized patients and those associated with long term care facilities. C. auris is frequently resistant to azoles such as Fluconazole, and the organism can  also be  resistant to the other classes of antifungals such as the echinocandins and polyenes (e.g., Amphotericin B).  In addition to being resistant to antifungals, C. auris  can cause persistent candidemia in patients which has resulted in high mortality rates (40-60%).

In the most recent communication from the CDC in July 2017 a total of 98 C. auris cases were reported  in United States. Ninety per cent of these cases (88) were isolates recovered from the NYC Metropolitan area ( 68 from NYC and 20 from New Jersey).  Four additional cases came from Illinois, and Indiana, Maryland, Massachusetts, Connecticut, Florida and Oklahoma each reported one case respectively.

It is believed that many more cases might exist, but this pathogen is under-reported due to the frequent laboratory practice of not identifying to the species level, Candida isolates which are not C. albicans. In addition, the common phenotypic methods used in clinical laboratories frequently misidentify C. auris as C. haemulonii, C. duobushaemuloniior or C. catenulate (by Vitek or Phoenix), or Rhodotorula glutinisor and C. sake (by API). The best methods to use for identification are the sequencing of the 28S rRNA genes and the internal transcriber spacer (ITS) of the RNA gene operon, as well as MALDI-TOF using research use only (RUO) libraries.

The microbiological features of C. auris include growth at 37 – 42oC, ovoid to elongate budding yeast on microscopy, and the absence of pseudohyphae or germ tubes. These characteristics help in differentiating C. auris from C haemulonii and C. duobushaemulonii since the latter two species form pseudohyphae with blastoconidia. In addition C. haemulonii does not grow at 42oC.  C. auris colonies are cream-colored on solid media (Figure 1) and pink in color on Candida CHROMagar. The CDC website provides guidance for the identification C. auris and also recommends  prompt communication and reporting to local and state public health laboratories as well as to the CDC at This email address is being protected from spambots. You need JavaScript enabled to view it..

Figure 1.C auris on Sabouraud dextrose agar.From CDC/ NCEZID; DFWED; MDB (Public Health Image Library)

The reference broth microdilution method is recommended  for antifungal susceptibility testing of C. auris. Commercially available susceptibility methods might overcall resistance particularly to Amphotericin B.  Although specific breakpoints have not yet been established, it is recommended that one use those available for other Candida species. The following are the current recommended  antifungal breakpoints:

Antifungal

MIC breakpoint for resistance (µg/mL)

Fluconazole

≥32

Amphotericin B

≥2

Anidulafungin

≥4

Caspofungin

≥2

Micafungin

≥4

Infection control measures are of particular importance for this organism.  C. auris  has been reported to form biofilms that persist in the environment contributing to its spread in healthcare institutions. The recommendations are that C. auris infected- patients be placed in a single-bed room and that Standard and Contact Precautions be followed. Hand hygiene must be strictly adhered to as well as daily and terminal room cleaning and disinfecting of the patient care area. It is also recommended that those having come in contact with infected patients be screened for C. auris colonization by culturing the axilla and groin.  Laboratorians handling C. auris cultures should follow standard laboratory safety practices including frequent hand hygiene.

In summary, the MDR C. auris has been reported in the NYC metropolitan area and we need to be vigilant in promptly identifying and reporting this organism. It is commonly misidentified by common commercial systems and might be resistant to several antifungal classes.

 

BIBLIOGRAPHY

-          Clinical alert to U.S. healthcare facilities – June 2016. Global emergence of invasive infections caused by the multi-drug resistant yeast Candida auris. https://www.cdc.gov/fungal/diseases/candidiasis/candida-auris-alert.html

-          Lockhart SR, et al. (2017). Simultaneous emergence of multi-drug resistant Candida auris on 3 continents confirmed by whole genome sequencing and epidemiological analysis. Clin Infect Dis 64:134-140

-          Chowdhary A, Sharma C, and Meis JF. (2017). Candida auris: a rapidly emerging cause of hospital-acquired multi-drug resistant fungal infections globally. PLoSPathog.13(5):91006290. https://doi.org/10.1371/journal.ppat.1006290

-          Tsay S, et al. (2017). Ongoing transmission of Candida auris in healthcare facilities – United States, June 2016 – May 2017. Morb Mort Wkly Rep. 66:514-515

-          Candida auris. Case count updated: July 14, 2017.  https://www.cdc.gov/fungal/diseases/candidiasis/candida-auris.html