Environmental Isolation of Candida auris from the Coastal Wetlands of Andaman Islands, India

Abstract

<i>Candida auris</i> is a multidrug resistant pathogen that presents a serious global threat to human health. As <i>C. auris</i> is a newly emerged pathogen, several questions regarding its ecological niche remain unexplored. While species closely related to <i>C. auris</i> have been detected in different environmental habitats, little is known about the natural habitat(s) of <i>C. auris</i> Here, we explored the virgin habitats around the very isolated Andaman Islands in the Indian Ocean for evidence of <i>C. auris</i> We sampled coastal wetlands, including rocky shores, sandy beaches, tidal marshes, and mangrove swamps, around the Andaman group of the Andaman & Nicobar Islands, Union Territory, in India. Forty-eight samples of sediment soil and seawater were collected from eight sampling sites representing the heterogeneity of intertidal habitats across the east and west coast of South Andaman district. <i>C. auris</i> was isolated from two of the eight sampling sites, a salt marsh and a sandy beach. Interestingly, both multidrug-susceptible and multidrug-resistant <i>C. auris</i> isolates were found in the sample. Whole-genome sequencing analysis clustered the <i>C. auris</i> isolates into clade I, showing close similarity to other isolates from South Asia. Isolation of <i>C. auris</i> from the tropical coastal environment suggests its association with the marine ecosystem. The fact that viable <i>C. auris</i> was detected in the marine habitat confirms <i>C. auris</i> survival in harsh wetlands. However, the ecological significance of <i>C. auris</i> in salt marsh wetland and sandy beaches to human infections remains to be explored.<b>IMPORTANCE</b><i>Candida auris</i> is a recently emerged multidrug-resistant fungal pathogen capable of causing severe infections in hospitalized patients. Despite its recognition as a human pathogen a decade ago, so far the natural ecological niche(s) of <i>C. auris</i> remains enigmatic. A previous hypothesis suggested that <i>C. auris</i> might be native to wetlands, that its emergence as a human pathogen might have been linked to global warming effects on wetlands, and that its enrichment in that ecological niche was favored by the ability of <i>C. auris</i> for thermal tolerance and salinity tolerance. To understand the mystery of environmental niches of <i>C. auris</i>, we explored the coastal wetland habitat around the very isolated Andaman Islands in the Indian Ocean. <i>C. auris</i> was isolated from the virgin habitats of salt marsh area with no human activity and from a sandy beach. <i>C. auris</i> isolation from the marine wetlands suggests that prior to its recognition as a human pathogen, it existed as an environmental fungus.