Candida auris is an emerging, often multidrug-resistant yeast that causes invasive infections (such as bloodstream, intra-abdominal) and is transmitted in health care settings. It is difficult to diagnose using traditional yeast identification methods. C. auris also has been found in noninvasive body sites and can colonize a person without causing active infection and hence permitting transmission of the pathogen between patients. These sites include skin, urine, external ear, wounds, and respiratory specimens.
This fungus was first described in 2009 in an ear-discharge culture from a patient in Japan. The first clinical cases were described in South Korea in 2011. An unknown pathogen before 2009, C. auris caused 4%-8% of candidemia in Indian ICUs during 2011-2012 and 38% of candidemia in one Kenyan hospital during 2010-2013. It has now spread across Asia and Europe, only to arrive in the United States in 2016.
As of Aug. 31, 2017, a total of 153 clinical cases of C. auris infection have been reported to CDC from 10 U.S. states; most have occurred in New York and New Jersey. An additional 143 patients have been found to be colonized with C. auris. Based on epidemiologic and molecular information, including whole genome sequencing, the Centers for Disease Control and Prevention infers that most U.S. cases likely resulted from local transmission of C. auris following previous introduction from other countries in Asia.
The majority of infections within the United States have been in blood streams. The reported all-cause mortality from these infections has been up to 60%. Most C. auris isolates in the United States have been resistant to at least one antifungal, most commonly fluconazole, and patients have developed resistance to echinocandin drugs while on treatment. Amphotericin B resistance also has been seen in about 30% of isolates.
In response to global reports and a large outbreak in a specialty hospital in the United Kingdom, the CDC issued its first advisory and clinical alert to health care facilities in June 2016. It is essential for hospitalist physicians to be aware of this emerging pathogen and also of the interventions needed to curb its spread, given they are the frontline warriors in the fight against hospital-acquired infections.
The first step in controlling C. auris is identification. C. auris can be misidentified when using traditional biochemical methods. They are most commonly misidentified as Candida haemulonii. Currently, accurate identification for C. auris can be performed by Vitek MS and matrix-assisted laser desorption/ionization time-of-flight using research use–only databases. Hospitalists should be aware of the diagnostic instruments used in their hospital laboratories and their ability to detect C. auris. Clinical laboratories should request testing of suspect C. auris isolates from their state or regional public health laboratory or the CDC. Laboratories should also consider reviewing historical microbiology records for suspect isolates (e.g., C. haemulonii) to identify missed cases of C. auris.
All cultures positive for Candida should be further speciated and antifungal susceptibilities should be reported as per new Infectious Diseases Society of America guidelines for candidiasis from 2016. As many clinical laboratories do not determine the species of Candida from noninvasive sites, C. auris colonization may go unrecognized and lead to transmission. About 54% of recognized U.S. clinical cases have been identified from blood cultures. The remaining patients with positive C. auris cultures, including those with recent hospitalizations abroad, have had the organism isolated from other body sites, including skin wounds, urine, respiratory specimens, bile fluid, and ears. Determining the species of Candida for isolates from these noninvasive sites in certain situations may allow for more rapid identification of C. auris and allow for timely implementation of targeted infection control measures to reduce transmission.
Patients have been persistently colonized with C. auris, posing long-term risk of transmission. Currently, data on effective decolonization methods are lacking. Patients with suspected or confirmed C. auris infection should be placed in a single room if possible and standard and contact precautions should be initiated and thorough environmental cleaning and disinfection of the patient care area should be undertaken. Using an Environmental Protection Agency–registered antimicrobial product active against Clostridium difficile for routine and terminal disinfection is recommended.
Implement contact tracing and testing to identify other patients colonized with C. auris. Review past microbiology records (at least for the preceding 1 year) for suspect or confirmed cases of C. auris at the institution. Set up enhanced surveillance for C. auris in the laboratory setting.
Echinocandin drugs are the first-line treatment for most invasive Candida infections, making resistance to this class of antifungal drugs particularly concerning. As of Sept. 15, 2017, at least five patients in the United States had echinocandin-resistant isolates. In one patient, resistance to echinocandin drugs developed while being treated with echinocandins.
Based on these findings, CDC is concerned that echinocandin-resistant C. auris could become more common. Patients with C. auris infection should be closely monitored for treatment failure, as indicated by persistently positive clinical cultures (lasting more than 5 days). Consultation with an infectious disease specialist is highly recommended.
Dr. Tirupathi is medical director, infectious diseases/HIV at Keystone Health, and chair, infection prevention, at Summit Health, both in Chambersburg, Pa. He is clinical assistant professor of medicine at Penn State University, Hershey.