Candida auris is an emerging multidrug-resistant yeast first described in 2009 that has since caused healthcare-associated outbreaks of severe human infections around the world. In some hospitals, it has become a leading cause of invasive candidiasis. C. auris is markedly different from most other pathogenic Candida species in its genetics, antifungal resistance, and ability to spread between patients. The reasons why this fungus began spreading widely in the last decade remain a mystery. We examine available data on C. auris and related species, including genomic epidemiology, phenotypic characteristics, and sites of detection, to put forth hypotheses on its possible origins. C. auris has not been detected in the natural environment; related species have been detected in in plants, insects, and aquatic environments, as well as from human body sites. It can tolerate hypersaline environments and higher temperatures than most Candida species. We explore hypotheses about the pre-emergence niche of C. auris, whether in the environmental or human microbiome, and speculate on factors that might have led to its spread, including the possible roles of healthcare, antifungal use, and environmental changes, including human activities that might have expanded its presence in the environment or caused increased human contact.

Zoonotic sporotrichosis is a neglected fungal disease, whereby outbreaks are primarily driven by Sporothrix brasiliensis and linked to cat-to-human transmission. To understand the emergence and spread of sporotrichosis in Brazil, the epicentre of the current epidemic in South America, we aimed to conduct whole-genome sequencing (WGS) to describe the genomic epidemiology. In this genomic epidemiology study, we included Sporothrix spp isolates from sporotrichosis cases from Brazil, Colombia, and the USA. We conducted WGS using Illumina NovaSeq on isolates collected by three laboratories in Brazil from humans and cats with sporotrichosis between 2013 and 2022. All isolates that were confirmed to be Sporothrix genus by internal transcribed spacer or beta-tubulin PCR sequencing were included in this study. We downloaded eight Sporothrix genome sequences from the National Center for Biotechnology Information (six from Brazil, two from Colombia). Three Sporothrix spp genome sequences from the USA were generated by the US Centers for Disease Control and Prevention as part of this study. We did phylogenetic analyses and correlated geographical and temporal case distribution with genotypic features of Sporothrix spp isolates. 72 Sporothrix spp isolates from 55 human and 17 animal sporotrichosis cases were included: 67 (93%) were from Brazil, two (3%) from Colombia, and three (4%) from the USA. Cases spanned from 1999 to 2022. Most (61 [85%]) isolates were S brasiliensis, and all were reported from Brazil. Ten (14%) were Sporothrix schenckii and were reported from Brazil, USA, and Colombia. For S schenckii isolates, two distinct clades were observed wherein isolates clustered by geography. For S brasiliensis isolates, five clades separated by more than 100 000 single-nucleotide polymorphisms were observed. Among the five S brasiliensis clades, clades A and C contained isolates from both human and cat cases, and clade A contained isolates from six different states in Brazil. Compared with S brasiliensis isolates, larger genetic diversity was observed among S schenckii isolates from animal and human cases within a clade. Our results suggest that the ongoing epidemic driven by S brasiliensis in Brazil represents several, independent emergence events followed by animal-to-animal and animal-to human transmission within and between Brazilian states. These results describe how S brasiliensis can emerge and spread within a country. Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil; the São Paulo Research Foundation; Productivity in Research fellowships by the National Council for Scientific and Technological Development, and Ministry of Science and Technology of Brazil.

We characterized 2 clusters of blastomycosis cases in Minnesota, USA, using whole-genome sequencing and single-nucleotide polymorphism analyses. Blastomyces gilchristii was confirmed as the cause of infection. Genomic analyses corresponded with epidemiologic findings for cases of B. gilchristii infections, demonstrating the utility of genomic methods for future blastomycosis outbreak investigations.

Histoplasmosis is one of the most under-diagnosed and under-reported endemic mycoses in the United States. Histoplasma capsulatum is the causative agent of this disease. To date, molecular epidemiologic studies detailing the phylogeographic structure of H. capsulatum in the United States have been limited. We conducted genomic sequencing using isolates from histoplasmosis cases reported in the United States. We identified North American Clade 2 (NAm2) as the most prevalent clade in the country. Despite high intra-clade diversity, isolates from Minnesota and Michigan cases were predominately clustered by state. Future work incorporating environmental sampling and veterinary surveillance may further elucidate the molecular epidemiology of H. capsulatum in the United States and how genomic sequencing can be applied to the surveillance and outbreak investigation of histoplasmosis.