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Sporothrix schenckii

Sporothrix schenckii colonies growing on Sabouraud's dextrose agar are shown in the upper image on the right. The organisms were obtained from a biopsy of an ulcerating skin lesion of the arm. The lower image is a lactophenol blue mount made from a portion of the colony. The colonies seen growing in the upper image have a gray-green, delicate, cottony consistency. The lactophenol blue mount reveals tiny, ovoid microconidia arranged in a daisy-head pattern at the tip of a straight conidiophore. This appearance is characteristic of the mold form of Sporothrix schenckii. By moving the focus up and down in a microscopic preparation, delicate hair-like attachments may be observed for each conidium.
The mold colonies of Sporothrix schenckii usually are initially moist and glabrous, almost yeast-like. In time the colony may darken, become wrinkled, folded, and covered with a low downy mycelium. At 37°C, yeast conversion of the colonies occurs, and pigmentation may vary, ranging from gray-yellow, to brown, to brown-black and finally jet black. Thus, S. schenckii must be included in the differential identification when an unknown fungus appears as a black yeast.
Sporotrichosis has been referred to as "rose growers' disease," because the organism can be found in rose thorns, as well as sphagnum moss, timbers, and soil. Sporotrichosis is not endemic to any particular geographic area and occurs worldwide.
Sporothrix schenckii may enter the body through a thorn prick. A pustule develops and ulcerates. It infects the lymphatic system and, in rare cases, could cause cutaneous lymphangitis. Sporotrichosis then progress up the arm with ulceration, abscess formation, and break down of the abscess with large amounts of pus.
Specimens that may be sent to the laboratory include pus, biopsy material, or sputum from pulmonary patients.