Sporothrix schenckii and General Aspects of Sporotrichosis

The thermally dimorphic fungus Sporothrix schenckii is the etiological agent of human and animal sporotrichosis and belongs to the recently proposed Sporothrix complex, which includes other species based on the phylogenetic-species concept. Sporotrichosis is a deep mycosis and clinical manifestations vary from a benign lymphocutaneous form to less frequent disseminated and extracutaneous forms, mainly associated with an immunocompromised host. Animals are also susceptible to S. schenckii infection and cats (Felis catus) are known for greater predisposition to this fungal infection. Only recently has zoonotic transmission of this disease been reported in greater detail in the literature and these new data are changing the epidemiological concept of this mycosis. The gold standard for the diagnosis of sporotrichosis remains fungus isolation from biological specimens, but new diagnostic tools are under development for both human and animal sporotrichosis. The outcome of an infectious disease is not only associated with virulence factors inherent to the pathogen, but also the host immune response. Thermotolerance is described as a virulence factor for S. schenckii and is associated with the capacity of a clinical or environmental isolate to cause host damage. However, the description of new species and genotypes among clinical isolates and the observation that thermotolerant isolates can exhibit differences in virulence using in vivo models strongly supports the concept that other virulence factors could be related to the clinical manifestations or modulate the host immune response. This chapter will address new data in relation to the clinical, epidemiological and biological aspects of S. schenckii.

Keywords: Sporothrix schenckii, sporotrichosis, epidemiology, virulence factors, host-fungus interplay, clinical diagnosis, saprophytic, thermotolerance, mycosis, taxonomy, phenotypic analysis.