Asexual Propagation of a Virulent Clone Complex in a Human and Feline Outbreak of Sporotrichosis

Abstract

Sporotrichosis is one of the most frequent subcutaneous fungal infections in humans and animals caused by members of the plant-associated, dimorphic genus Sporothrix. Three of the four medically important Sporothrix species found in Brazil have been considered asexual as no sexual stage has ever been reported in Sporothrix schenckii, Sporothrix brasiliensis, or Sporothrix globosa. We have identified the mating type (MAT) loci in the S. schenckii (strain 1099-18/ATCC MYA-4821) and S. brasiliensis (strain 5110/ATCC MYA-4823) genomes by using comparative genomic approaches to determine the mating type ratio in these pathogen populations. Our analysis revealed the presence of a MAT1-1 locus in S. schenckii while a MAT1-2 locus was found in S. brasiliensis representing genomic synteny to other Sordariomycetes. Furthermore, the components of the mitogen-activated protein kinase (MAPK)-pheromone pathway, pheromone processing enzymes, and meiotic regulators have also been identified in the two pathogens, suggesting the potential for sexual reproduction. The ratio of MAT1-1 to MAT1-2 was not significantly different from 1:1 for all three Sporothrix species, but the population of S. brasiliensis in the outbreaks originated from a single mating type. We also explored the population genetic structure of these pathogens using sequence data of two loci to improve our knowledge of the pattern of geographic distribution, genetic variation, and virulence phenotypes. Population genetics data showed significant population differentiation and clonality with a low level of haplotype diversity in S. brasiliensis isolates from different regions of sporotrichosis outbreaks in Brazil. In contrast, S. schenckii isolates demonstrated a high degree of genetic variability without significant geographic differentiation, indicating the presence of recombination. This study demonstrated that two species causing the same disease have contrasting reproductive strategies and genetic variability patterns.

Sporothrix brasiliensis outbreaks and the rapid emergence of feline sporotrichosis

“…Thus, cats remain the main source of infection of S. brasiliensis in South and Southeast Brazil. 1,3,12,18,30 It is remarkable that close related Sporothrix, i.e. S. schenckii s. str.…”

“…Indeed, the high number of cases in a short period is compatible with the ongoing situation reported earlier in other endemic areas of Brazil. [1][2][3]6,12,14,15,19,20,28,29 The real prevalence of feline sporotrichosis is likely to be underestimated in Southern Brazil, since it is not an obligatorily reported disease. We considered only the cases referred to FAMED-FURG and with confirmed laboratorial diagnosis of sporotrichosis, i.e., by isolation of Sporothrix in culture.…”

“…1,2 Zoonotic sporotrichosis outbreaks have been described since the 1990's and are emerging as an important infectious disease in South and Southeast Brazil. 3,[11][12][13][14][15][16][17][18] These cases are mainly associated with S. brasiliensis, 1,3 and domestic cats play key roles in disease epidemiology. Cats are highly susceptible to Sporothrix infection, developing multiple skin lesions with a great load of yeast-like cells.…”

Which MAT gene? Pezizomycotina (Ascomycota) mating-type gene nomenclature reconsidered

“…Some authors also consider an intron present in a conserved position within the MATα1 domain ( Figure 3) as characteristic of the MAT1-1-1 gene (Kanematsu et al, 2007;Waalwijk et al, 2002;Wilken et al, 2014), although this intron might not be universally present (e.g. the human pathogen Sporothrix schenckii; Teixeira et al, 2015).…”

A population genetics analysis in clinical isolates of Sporothrix schenckii based on calmodulin and calcium/calmodulin‐dependent kinase partial gene sequences

“…Furthermore, recent studies of fungal collections have demonstrated the presence of S. mexicana and S. globosa in clinical samples obtained from patients since 1955 . S. brasiliensis was reported in Brazilian mammalian outbreaks over the last few decades, highlighted by the contamination of semi‐domestic felines ( Felis catus ) with transmission to humans . In Mexico, sporadic infection by cats has been documented, even though S. brasiliensis has not been reported in this country.…”