Dimorphic fungi - Sporothrix schenckii

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Dimorphic fungi - Sporothrix schenckii

Sporothorix schenckii produces elongated (cigar-shaped) yeast cells that measure 4-6 µm and bud at a narrow base. The mold form grows moderately to rapidly when cultured at 25-30ºC. The colonies are moist and white to pale orange, initially, turning brown with age.
Very delicate, hyaline, septate hyphae are produced, and conidiophores are often seen with clusters (rosettes) of microconidia surrounding their tips. Definitive identification requires the conversion of the mold form to the yeast form, which produce tan to brown, creamy colonies. The yeast cells are oval or long and thin ("cigar bodies"), and bud at a narrow base.
The disease sporotrichosis is seen worldwide, although most cases occur in North and South America. Penetrating injury from contaminated plant material (rose gardener disease) or soil is the usual route of infection. Lymphocutaneous infection, with nodular ulcerative skin lesions following lymphatics is the most common clinical manifestation.
The top right image shows a S. schenckii culture plate. The bottom right image shows a lactophenol cotton blue preparation of S. schenckii showing the organism's ovoid or cigar-shaped conidia, some of which arise from the septate hyphae individually or in clusters, while, the conidiophore is seen in the center topped by a cluster of conidia.
Images courtesy of the CDC.