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SPOROTHRIX Mold SpeciesThe U.S. Government's Occupational Safety and Health Administration [OSHA] lists the following as the health effects of Sporothrix mold: Allergen, Irritant, Hypersensitivity pneumonitis, Dermatitis. |
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Description and Habitats According to de Hoog (1993), species of Sporothrix have been reported as anamorphs of both ascomycetes and basidiomycetes. However, he believes the name should be restricted to those with ascomycetous relationships and refers the basidiomycetous ones to the genus Cerinosterus. Unfortunately, distinguishing Sporothrix from Cerinosterus with certainty requires an electron microscope or advanced biochemical techniques. Isolated from soil, decaying plant materials, other fungi, insects, and air. Sometimes causing human disease. Holomorphs: Ophiostoma, Pseudeurotium, Thecotheus, Stephanoascus, Valsonectria, and others. Ref: de Hoog 1974, 1993 SpeciesThe genus Sporothrix contains three active species. The most common one is Sporothrix schenckii, followed by Sporothrix cyanescens. Health Effects Sporotrichosis is usually a chronic infection of the cutaneous or subcutaneous tissue which tends to suppurate, ulcerate and drain. In recent years, a pulmonary disease has been seen more frequently. Occasionally, infection with S. schenckii may result in a mycetoma. Sporotrichosis is caused by another dimorphic fungus. The infection is also known as "rose growers disease." The ecologic niche for this organism is rose thorns, sphagnum moss, timbers and soil. A study on the occupational distribution of sporotrichosis showed that forest employees accounted for 17% of the cases, gardeners and florists, 10%; and other soil-related occupations another 16%. Sporotrichosis occurs worldwide. Every aspect of this disease (clinical, pathology, mycology, ecology) was investigated during an epidemic of 3,000 patients in a gold mine in South Africa during the 1940's. Patient history is very important in this disease also. It is often seen in gardeners and begins with a thorn prick on the thumb. A pustule develops and ulcerates. It infects the lymphatic system and then the disease progresses up the arm with ulceration, abscess formation, break down of the abscess with large amounts of pus followed by healing. Progression usually stops at the axilla. Clinical material to be sent to the lab may be pus, biopsy material, or sputum from pulmonary patients. The yeast form of this fungus in tissue or in culture, can be round (6-8 um) or fusiform. The fusiform shape is not the usual form but if a cigar-shaped yeast is observed in tissue, it is usually diagnostic of sporotrichosis. S. schenckii does not stain with the usual histopathological stains. If sporotrichosis is suspected, the pathologist must be informed so he can use special stains. Histologically asteroid bodies, a tissue reaction (also known as Splendori reaction) may be seen around the yeast cell. At 25 degrees C, this colony is white-cream and very membranous, but as it ages for 2-3 weeks it becomes black and leathery. Microscopically, the mycelium is branching, septate and very delicate, 2-3 um in diameter. The pyriform conidia, 2-4 um form a typical arrangement in groups at the end of a conidiophore called "daisies." Serologic tests are not commercially available. The drug of choice for the cutaneous form is saturated iodides (e.g., potassium iodide) administered orally. The patient begins with 2-3 drops, 3-4/days until tolerance to the drug is built up, then the dose is increased. Potassium iodide may interact with the host immune system. For the systemic form the drug of choice is itraconazole or amphotericin B. Macroscopic
Features I. Sporothrix schenckii. It is a thermally dimorphic fungus and the
colony morphology varies depending on the temperature of growth. At 25°C,
colonies grow moderately rapidly. They are moist, leathery to velvety, and
have a finely wrinkled surface. From the front and the reverse, the color
is white initially and becomes cream to dark brown in time ("dirty
candle-wax" color). At 37°C, colonies grow moderately rapidly. They
are yeast-like and creamy. The color is cream to beige. The conversion of
the mold form to the yeast form is required for definitive identification
of Sporothrix schenckii. Microscopic
Features I.
Sporothrix schenckii. Similar to its colony morphology, microscopic
features of Sporothrix schenckii also vary depending on the
temperature of growth. At 25°C, septate hyaline hyphae, conidiophores,
and conidia are observed. Conidiophores are sympodial and appear weakly
differentiated from the vegetative hyphae. They often have an inflated
base and arise at right angles from the hyphae. Conidia have two types.
The first type are unicellular, hyaline to brown, oval, thin-walled, and
are typically arranged in rosette-like clusters at the tips of the
conidiophores. The second type of conidia are brown (dematiaceous),oval or
triangular, thick-walled, cessile, and are attached directly to the sides
of the hyphae. The latter type of conidia are typically present only in
freshly isolated strains. At 37°C, Sporothrix schenckii produces
oval to cigar-shaped (also called "cigar bodies") yeast cells.
Single or multiple buds may be produced by a single yeast cell. Laboratory
Precautions No
special precautions other than general laboratory precautions are
required. Susceptibility Available
data suggest that in vitro activity of amphotericin
B and itraconazole
against Sporothrix schenckii is variable and strain-dependent.
(Primary) amphotericin B-resistant isolates have been identified. Terbinafine,
naftifine,
and amorolfine
are active in vitro against Sporothrix schenckii. On the other
hand, fluconazole,
voriconazole
and ravuconazoleyield
high MICs for isolates of Sporothrix schenckii. |
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The mycological information gathered and organized in
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