Scedosporium Mold SpeciesScedosporium species is a causative agent of Brain Abscess, Mycetoma, Hyalohyphomycosis, and Phaeohyphomycosis. (Information from www.doctorfungus.org @ 2005)
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Taxonomic Classifications
Kingdom:
Fungi
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Ecology Scedosporium is a cosmopolitan filamentous fungus which is commonly isolated from rural soils, from polluted water, from composts, and from manure of cattle and fowl. Scedosporium occasionally causes infections in humans.
Species The genus Scedosporium contains two species namely, Scedosporium apiospermum and Scedosporium prolificans. There is no sexual form or teleomorph known for Scedosporium prolificans while Pseudallescheria boydii is the teleomorph of Scedosporium apiospermum.
Pathogenicity and Health Effects Both immunocompetent and immunocompromised hosts can be infected by Scedosporium prolificans. Subcutaneous infections, osteomyelitis, and arthritis are commonly post – traumatic and may affect otherwise healthy individuals.
Due to various reasons, on the other hand, disseminated infections which are often fatal are generally encountered in immunosuppressed neutropenic patients. Scedosporium prolificans is now the known common causative agent of disseminated phaeohyphomycosis. Scedosporium prolificans has been reported to cause ocular infections (keratouveitis) and colonization. Cases with pneumonia, meningoencephalitis, and endocarditis have also been reported.
Macroscopic Appearance Ø Growth rate is very rapid at 25°C and colonies are initially cottony and moist (yeast – like) becoming flat with fine, short, mycelial tufts in texture in maturation; and Ø The surface colony color is light gray to black becoming dark gray to black in time while reverse is gray to black;
Microscopic Appearance Ø Septate hyaline hyphae, conidiogenous cells (annellides), and conidia are present; Ø Annellides may form directly from hyphae or are formed at the tips of the conidiophores, flask – shaped with swollen base part and elongated neck; Ø Conidia are oval – shaped, olive to brown in color, with a slightly narrowed, truncated base, unicellular, with size of 2 – 5 x 3 – 13 µm, and appear in clusters at the tips of the annellides; Additionally, some isolates may produce round, thick – walled conidia which are formed directly from the hyphae (present in Scedosporium asexual state); and Ø After two to three weeks of incubation, brown cleistothecia are often present in the sexual state of Pseudallescheria boydii.
Laboratory Precautions General laboratory precautions are required, no special safety measures needed.
Susceptibility Scedosporium prolificans is resistant to amphotericin B, flucytosine, ketoconazole, miconazole, fluconazole, and itraconazole. Showed no or very limited in vitro activities against Scedosporium prolificans isolates are voriconazole, the novel triazole Syn – 2869 and caspofungin.
Although either itraconazole or terbinafine has no activity against most isolates of Scedosporium prolificans, the combination of these two drug agents proved to be active in in vitro 95% of the isolates after 48 hours of incubation. Additionally, in this combination study antagonism was not observed.
Treatment of infections caused by Scedosporium prolificans is difficult due to its primary multi – resistant nature. Therapy of amphotericin B alone or in combination with flucytosine, fluconazole, or itraconazole has been used in Scedosporium prolificans - infection cases. The mortality rate, however, has been very high in most disseminated infection cases. Liposomal amphotericin B combined with G - CSF seemed to improve survival in an immunocompromised murine model with disseminated Scedosporium prolificans infection. Post – traumatic infections which include arthritis in immunocompetent cases have responded to fluconazole or surgical debridement alone.
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