Candida auris is a species of fungus which grows as yeast, first described in 2009. It is one of the few species of the Candida genus which cause candidiasis in humans. Candidiasis is often acquired in hospitals by patients with weakened immune systems. C. auris can cause invasive candidiasis in which the bloodstream (fungemia), the central nervous system, and internal organs are infected. It has recently attracted increased attention because of its multidrug resistance. Treatment is also complicated because it is easily misidentified as other Candida species. C. auris was first described after it was isolated from the ear canal of a 70-year-old Japanese woman at the Tokyo Metropolitan Geriatric Hospital in Japan in 2009. The first cases of disease-causing C. auris were reported from South Korea in 2011, spread across Asia and Europe to arrive in the U.S. in 2016.
Identification and morphology
Candida auris is a species of ascomycetous fungus, of the Candida genus, which grows as yeast, first described in 2009. Its name comes from the Latin word for ear, auris,. It forms smooth, shiny, whitish-gray, viscous colonies on growth media. Microscopically cells are ellipsoid in shape.
Candida auris is one of the few Candida species which can cause candidiasis in humans. Candidiasis is often acquired in hospitals by patients with weakened immune systems. It can cause invasive candidiasis, in which the blood stream is invaded (fungemia), the central nervous system, kidneys, liver, bones, muscles, joints, spleen, or eyes. C. auris has attracted increased clinical attention because of its multidrug resistance.
Treatment is complicated because C. auris is easily misidentified as other Candida species. A brief outline of its clinical relevance as of 2016, understandable by general audiences, was published by the Center for Infectious Disease Research and Policy at the University of Minnesota.
Several draft genomes from whole genome sequencing have been published. The C. auris genome was found to encode several genes for the ABC transporter family and major facilitator superfamily which helps to explain its multidrug resistance. Its genome also encodes virulence-related gene families such as lipases, oligopeptide transporters, mannosyl transferases and transcription factors which facilitate colonization, invasion and iron acquisition. Another factor contributing to antifungal resistance is the presence of a set of genes known to be involved in biofilm formation.
More studies are needed to determine if the phylogenetic divergence of C. auris clones exhibits region-specific patterns of invasiveness, virulence, and/or drug resistance.
The phylogenetics of C. auris suggest distinct genotypes exist in different geographical regions with substantial genomic diversity. A variety of sequence-based analytical methods have been used to support this finding.
Whole genome sequencing and analyses of isolates from Pakistan, India, South Africa, Venezuela, Japan and previously sequenced C. auris genomes deposited in the National Center for Biotechnology Information’s Sequence Read Archive  identified a distinct geographic distribution of genotypes. Four distinct clades separated by tens of thousands of single-nucleotide polymorphisms were identified. The distribution of these clades segregated geographically to South Asia (India and Pakistan), South Africa, Venezuela and Japan with minimal observed intraregion genetic diversity.
Amplified fragment length polymorphism analysis of C. auris isolates from the United Kingdom, India, Japan, South Africa, South Korea, and Venezuela suggested that the London isolates formed a distinct cluster compared to the others.
Comparison of ribosomal DNA sequences of C. auris isolates from Israel, Asia, South Africa and Kuwait found that the strains from Israel were phylogenetically distinct from those from the other regions. Chatterjee et al. wrote in 2015, "Its actual global distribution remains obscure as the current commercial methods of clinical diagnosis misidentify it as C. haemulonii."
C. auris was first described after it was isolated from the ear canal of a 70-year-old Japanese woman at the Tokyo Metropolitan Geriatric Hospital in Japan. It was isolated based on its ability to grow in the presence of the fungicide micafungin, an echinocandin class fungicide. Phenotypic, chemotaxonomic and phylogenetic analyses established C. auris as a new strain of the genus Candida.
The first three cases of disease-causing C. auris were reported from South Korea in 2011. Two isolates had been obtained during a 2009 study and a third was discovered in a stored sample from 1996. All three cases had persistent fungemia, i.e. bloodstream infection, and two of the patients subsequently died due to complications. Notably, the isolates were initially misidentified as Candida haemulonii and Rhodotorula glutinis using standard methods until sequence analysis correctly identified them as C. auris. These first cases emphasize the importance of accurate species identification and timely application of the correct antifungal for the effective treatment of candidiasis with C. auris.
During 2009–2011, 12 C. auris isolates were obtained from patients at two hospitals in Delhi, India. The same genotype was found in distinct settings: intensive care, surgical, medical, oncologic, neonatal, and pediatric wards, which were mutually exclusive with respect to health care personnel. Most had persistent candidemia and a high mortality rate was observed. All isolates were of the same clonal strain and were only identified positively by DNA sequence analysis. As previously, the strain was misidentified with established diagnostic laboratory tests. The Indian researchers wrote in 2013 that C. auris was much more prevalent than published reports indicate since most diagnostic laboratories do not use sequence-based methods for strain identification.
The fungus spread to other continents, and in early 2016, a multi-drug-resistant strain was eventually discovered in Southeast Asian countries.
In April 2017, CDC director Anne Schuchat named it a "catastrophic threat". As of May 2017[update] the CDC had reported 77 cases in the United States on its website. Of these 69 were from samples collected in New York and New Jersey.
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