Over the past decade or so, there has been a concerning emergence of a drug-resistant fungus known as Candida auris that has had impacts in the US and abroad. In fact, in 2013, the US CDC listed fluconazole-resistant Candida as one of the top 18 antimicrobial-resistant threats in the US, and in 2018, it became a nationally notifiable disease at the Council for State and Territorial Epidemiologists Annual Conference. Outbreak Observatory has written previously about C. auris, and will provide a brief update on this growing public health threat in this week’s post.
Some of the risk factors for C. auris infection include recent surgery, chronic disease, presence of invasive medical monitoring devices, and broad-spectrum antibiotic and antifungal use; thus, outbreaks in hospitals, where many individuals with these risk factors reside, are most common. Although there is limited data, approximately 30-60% of people with C. auris infections die, a number that is likely impacted by the presence of other serious diseases in affected populations. While some C. auris infections are treatable, one of the growing concerns is that some are resistant to all three main classes of antifungals, making them difficult to treat. Although it is not completely understood why drug-resistant fungi such as C. auris are emerging, some researchers theorize that the heavy use of fungicides in agriculture might be playing a part.
Around half of clinical cases in the US are identified through isolation of C. auris from the bloodstream, and the CDC recommends that “all yeast isolates obtained from a normally sterile site (e.g., bloodstream) be identified to the species level,” which helps ensure proper treatment. However, Candida species are also often isolated from non-sterile sites, and laboratories do not usually determine the specific species of these isolates because it may indicate colonization rather than infection. However, the CDC does recommend species-level identification when a number of other circumstances are present, including when C. auris has been detected in a unit or facility or when the patient has a recent history of hospitalization in another country. The CDC also has screening recommendations for those patients who are considered at high risk for C. auris, which includes close contact with other patients with C. auris infection or colonization, and patients who have a history of hospitalization in another country, particularly if that country has documented C. auris cases. The CDC also recommends more extensive screening if there is ongoing transmission within a facility. However, surveillance and detection can be challenging, as C. auris is difficult to detect with standard laboratory methods, and if often mistaken for other types of yeasts, leading to mismanagement of patients and the potential for continued spread within hospital settings.
As of the end of February 2019, there have been a total of 587 confirmed cases of C. auris reported by 12 US states. The majority of cases (309) have been reported in the state of New York. One recent article published in the CDC journal Emerging Infectious Diseases described an outbreak in NYC healthcare facilities. The researchers identified 51 clinical cases of C. auris, and all but one were resistant to fluconazole, and 13 were resistant to both fluconazole and amphotericin B. The researchers also identified 61 screening cases (i.e., those who were identified for surveillance purposes). Epidemiologic links between the cases “revealed a large, interconnected web of affected healthcare facilities throughout NYC,” highlighting the need for enhanced infection control measures to prevent additional outbreaks, including hand washing, room signage, and PPE use. The reasons why there is such a large number of cases in New York is unknown, but the authors suggest a number of possibilities, including New York’s position as a international travel hub, providing multiple opportunities for introduction; more aggressive case finding; and the interconnectedness of NYC’s healthcare facilities. New Jersey and Illinois have also seen large amounts of cases. Cases have also been reported around the globe, and some US cases have reported recent travel and hospitalizations in countries with documented transmission.
The emergence of antifungal resistance poses a serious threat to global health security. An article in Science published in 2018 called for the development of new antifungals, antifungal stewardship, and integrated disease management to help improve fungal control strategies. Surveillance mechanisms must also be improved so that we can have a better understanding of the scope of the problem, and to prevent further outbreaks. The development of new diagnostics, such as one real-time PCR assay described in the Journal of Clinical Microbiology, that can rapidly--and correctly--identify C. auris, and proper infection control measures will be critically important to preventing further transmission and loss of life.
Outbreak Observatory aims to collect information on challenges and solutions associated with outbreak response and share it broadly in near-real time to allow others to learn from these experiences in order to improve global outbreak response capabilities.
Photo courtesy of CDC/Shawn Lockhart