Biology subjects

Litvintseva, A. P.

Publications and source records attributed to Litvintseva, A. P..

5 recordsLinked to original sources

bioRxiv2023

Finding Candida auris in public metagenomic repositories

Candida auris is a newly emerged multidrug-resistant fungus capable of causing invasive infections with high mortality. Despite intense efforts to understand how this pathogen rapidly emerged and spread worldwide, its environmental reservoirs are poorly understood. Here, we present a collaborative effort between the U.S. Centers for Disease Control and Prevention, the National Center for Biotechnology Information, and GridRepublic (a volunteer computing platform) to identify C. auris sequences in publicly available metagenomic datasets. We developed the MetaNISH pipeline that uses SRPRISM to align sequences to a set of reference genomes and computes a score for each reference genome. We used MetaNISH to scan [~]300,000 SRA metagenomic runs from 2010 onwards and identified five datasets containing C. auris reads. Finally, GridRepublic has implemented a prospective C. auris molecular monitoring system using MetaNISH and volunteer computing.

bioinformatics↗

bioRxiv2020

Tracing the evolutionary history and global expansion of Candida auris using population genomic analyses

Candida auris has emerged globally as a multidrug-resistant yeast that can spread via nosocomial transmission. An initial phylogenetic study of isolates from Japan, India, Pakistan, South Africa, and Venezuela revealed four populations (Clades I, II, III, and IV) corresponding to these geographic regions. Since this description, C. auris has been reported in over 30 additional countries. To trace this global emergence, we compared the genomes of 304 C. auris isolates from 19 countries on six continents. We found that four predominant clades persist across wide geographic locations. We observed phylogeographic mixing in most clades; Clade IV, with isolates mainly from South America, demonstrated the strongest phylogeographic substructure. C. auris isolates from two clades with opposite mating types were detected contemporaneously in a single healthcare facility in Kenya. We estimated a Bayesian molecular clock phylogeny and dated the origin of each clade within the last 339 years; outbreak-causing clusters from Clades I, III, and IV originated 34-35 years ago. We observed high rates of antifungal resistance in Clade I, including four isolates resistant to all three major classes of antifungals. Mutations that contribute to resistance varied between the clades, with Y132F in ERG11 as the most widespread mutation associated with azole resistance and S639P in FKS1 for echinocandin resistance. Copy number variants in ERG11 predominantly appeared in Clade III and were associated with fluconazole resistance. These results provide a global context for the phylogeography, population structure, and mechanisms associated with antifungal resistance in C. auris. ImportanceIn less than a decade, C. auris has emerged in healthcare settings worldwide; this species is capable of colonizing skin and causing outbreaks of invasive candidiasis. In contrast to other Candida species, C. auris is unique in its ability to spread via nosocomial transmission and its high rates of drug resistance. As part of the public health response, whole-genome sequencing has played a major role in characterizing transmission dynamics and detecting new C. auris introductions. Through a global collaboration, we assessed genome evolution of isolates of C. auris from 19 countries. Here, we described estimated timing of the expansion of each C. auris clade and of fluconazole resistance, characterized discrete phylogeographic population structure of each clade, and compared genome data to sensitivity measurements to describe how antifungal resistance mechanisms vary across the population. These efforts are critical for a sustained, robust public health response that effectively utilizes molecular epidemiology.

genomics↗

bioRxiv2019

Chromosomal rearrangements and loss of subtelomeric adhesins linked to clade-specific phenotypes in Candida auris

Candida auris is an emerging fungal pathogen of rising concern due to its increasing incidence, its ability to cause healthcare-associated outbreaks and antifungal resistance. Genomic analysis revealed that early cases of C. auris that were detected contemporaneously were geographically stratified into four major clades. Clade II, also termed East Asian clade, consists of the initial isolates described from cases of ear infection, is less frequently resistant to antifungal drugs and to date, the isolates from this group have not been associated with outbreaks. Here, we generate nearly complete genomes (\"telomere-to-telomere\") of an isolate of this clade and of the more widespread Clade IV. By comparing these to genome assemblies of the other two clades, we find that the Clade II genome appears highly rearranged, with 2 inversions and 9 translocations resulting in a substantially different karyotype. In addition, large subtelomeric regions have been lost from 10 of 14 chromosome ends in the Clade II genomes. We find that shorter telomeres and genome instability might be a consequence of a naturally occurring loss-of-function mutation in DCC1 exclusively found in Clade II isolates, resulting in a hypermutator phenotype. We also determine that deleted subtelomeric regions might be linked to clade-specific adaptation as these regions are enriched in Hyr/Iff-like cell surface proteins, novel candidate cell surface proteins, and an ALS-like adhesin. The presence of these cell surface proteins in the clades responsible for global outbreaks causing invasive infections suggests an explanation for the different phenotypes observed between clades.\n\nIMPORTANCECandida auris was unknown prior to 2009 and since then it has quickly spread around the world, causing outbreaks in healthcare facilities and representing a high fraction of candidemia cases in some regions. The emergence of C. auris is a major concern, since it is often multidrug-resistant, easily spread between patients, and causes invasive infections. While isolates from three global clades cause invasive infections, isolates from Clade II primarily cause ear infections and have not been implicated in outbreaks, though cases of Clade II infections have been reported on different continents. Here, we describe genetic differences between Clade II and Clades I, III and IV, including a loss-of-function mutation in a gene associated with telomere length maintenance and genome stability, and the loss of cell wall proteins involved in adhesion and biofilm formation, that may suggest an explanation for the lower virulence and potential for transmission of Clade II isolates.

genomics↗

bioRxiv2019

Strong population structure in Venezuelan populations of Coccidioides posadasii

Coccidioides posadasii is a pathogenic fungus that causes coccidioidomycosis in many arid regions of the Americas. One of these regions is bordered by the Caribbean Sea, and the surrounding landscape may play an important role in the dispersion of C. posadasii across South America through southeastern Mexico, Honduras, Guatemala and Venezuela. Comparative phylogenomic analyses of C. posadasii reveal that clinical strains from Venezuela are genetically distinct from the North American populations found in Arizona (AZ), Texas, Mexico, and the rest of South America (TX/MX/SA). We find evidence for admixture between the Venezuela and the North American populations of C. posadasii in Central America. As expected, the proportion of Venezuelan alleles in the admixed population decreases as latitude (and distance from Venezuela) increases. Our results indicate that the population in Venezuela may have been subjected to a recent bottleneck, and shows strong population structure. This analysis provides insight into potential for Coccidioides spp. to invade new regions.

evolutionary biology↗

bioRxiv2018

Genomic basis of multidrug-resistance, mating, and virulence in Candida auris and related emerging species

Candida auris is an emergent fungal pathogen of rising public health concern due to increasing reports of outbreaks in healthcare settings and resistance to multiple classes of antifungal drugs. While distantly related to the more common pathogens C. albicans and C. glabrata, C. auris is closely related to three rarely observed and often multidrug-resistant species, C. haemulonii, C. duobushaemulonii and C. pseudohaemulonii. Here, we generated and analyzed near complete genome assemblies and RNA-Seq-guided gene predictions for isolates from each of the four major C. auris clades and for C. haemulonii, C. duobushaemulonii and C. pseudohaemulonii. Our analyses mapped seven chromosomes and revealed chromosomal rearrangements between C. auris clades and related species. We found conservation of genes involved in mating and meiosis and identified both MTLa and MTL C. auris isolates, suggesting the potential for mating between clades. Gene conservation analysis highlighted that many genes linked to drug resistance and virulence in other pathogenic Candida species are conserved in C. auris and related species including expanded families of transporters and lipases, as well as mutations and copy number variants in ERG11 that confer drug resistance. In addition, we found genetic features of the emerging species that likely underlie differences in virulence and drug response between these and other Candida species, including genes involved in cell wall structure. To begin to characterize the species-specific genes important for antifungal response, we profiled the gene expression of C. auris in response to voriconazole and amphotericin B and found induction of several transporters and metabolic regulators that may play a role in drug resistance. This study provides a comprehensive view of the genomic basis of drug resistance, potential for mating, and virulence in this emerging fungal clade.

genomics↗