Sporotrichosis: an overview and therapeutic options

Abstract

Sporotrichosis is a chronic granulomatous mycotic infection caused by Sporothrix schenckii, a common saprophyte of soil, decaying wood, hay, and sphagnum moss, that is endemic in tropical/subtropical areas. The recent phylogenetic studies have delineated the geographic distribution of multiple distinct Sporothrix species causing sporotrichosis. It characteristically involves the skin and subcutaneous tissue following traumatic inoculation of the pathogen. After a variable incubation period, progressively enlarging papulo-nodule at the inoculation site develops that may ulcerate (fixed cutaneous sporotrichosis) or multiple nodules appear proximally along lymphatics (lymphocutaneous sporotrichosis). Osteoarticular sporotrichosis or primary pulmonary sporotrichosis are rare and occur from direct inoculation or inhalation of conidia, respectively. Disseminated cutaneous sporotrichosis or involvement of multiple visceral organs, particularly the central nervous system, occurs most commonly in persons with immunosuppression. Saturated solution of potassium iodide remains a first line treatment choice for uncomplicated cutaneous sporotrichosis in resource poor countries but itraconazole is currently used/recommended for the treatment of all forms of sporotrichosis. Terbinafine has been observed to be effective in the treatment of cutaneous sporotrichosis. Amphotericin B is used initially for the treatment of severe, systemic disease, during pregnancy and in immunosuppressed patients until recovery, then followed by itraconazole for the rest of the therapy.

Figure 1

Lymphocutaneous sporotrichosis. Noduloulcerative lesions appear along the lymphatics proximal to the initial inoculation injury site.

Figure 2

Fixed cutaneous sporotrichosis. A crusted/verrucous plaque develops at inoculation site, seen here over face of a child.

Figure 3

Sporothrix schenckii colony on Sabouraud's glucose agar (SDA) at 25°C. Initial cream color turns brown black as it matures.

Figure 4

(a) Sporothrix schenckii from culture on SDA at 25°C. Seen here is delicate branching, mold form with pyriform conidia in characteristic flower-like arrangement or sleeve-like pattern (stain-lactophenol cotton blue ×40). (b) Yeast phase of Sporothrix schenckii isolate from culture on brain heart infusion agar at 37°C. Budding yeast cells (thick arrows) and cigar shaped yeast cells (thin arrows) interspersed between spores (Grams' stain, ×100) are seen here.