Climate changes and emerging fungal infections

Background: Candida auris is a globally emerging yeast pathogen that has shown not only resistance to most anti-fungal drugs but also thermo-tolerance to temperatures higher than the mammalian’s body temperature. Although it has been only a decade since the fungus was identified, its spread of infections has been rapid and quasi-epidemics have been reported. Co-occurrences of the fungus infections in all five continents are one of the strangest aspects of this fungus. All isolates, despite slight genetic differences, belong to a common genetic ancestor. However, different clades appear to have independent evolutionary paths. We have discussed the relationship between the acquired thermal tolerance of C. auris and the environmental temperature changes with the genetic affinities of the isolates. Methods: This basic science survey was carried out at the Shiraz University of medical sciences from July to December 2019. Phylogenetic analysis was used to compare the temperature sensitivity of C. auris and the species with which it is genetically related. The sequences of Internal transcribed spacer (ITS) region and the growth temperature ranges for C. auris and yeasts belonging to the Candida haemulonis complex as well as other environmental yeasts isolated from different geographical areas of the world were randomly selected and evaluated. Their phylogenetic relationship was investigated with the mapping of the phylogenetic tree based on ITS sequences. Results: Study of temperature ranges which the fungi are capable of growing clearly shows that all species of C. auris can tolerate temperatures higher than the mammalian body temperature. Genetic distances, as well as geographic distances between species of C. auris are visible during phylogenetic studies. These results illustrate the possibility that, despite these distances, the temperature tolerance attribute for each C. auris clade was independently and under a common external pressure such as global warming. Conclusion: The results of this study have discussed the increased incidence of emerging fungal infections due to climate changes; however the role of other contributing factors in the spread of these infections needs further investigation.