Colony grows rapidly, with wooly to cottony texture, a white surface that browns as it ages, and a pale reverse with brownish black zones.
Microscopic appearance
Septate, hyaline hyphae with annellide conidiophores that are simple or branched
Onidia are unicellular, obovoid, and pale brown
Sometimes has a Graphium state where conidiophores are bound together
Brown cleistothecia may be present after 2-3 weeks of incubation (looks like a Pacman vomiting out conidia)
Epidemiology
Found in rural soils, polluted waters, compost, cattle manure, and bird poop, as well as colonizing the respiratory tract
Present worldwide
Affects primarily the immunocompromised, though can cause localized infections in immunocompetent as well
Clinical Manifestations
Colonization of airways, especially in bronchiectasis
Pseudallescheria boydii (Scedosporium apiospermum) can cause mycetoma, and also pseudallescheriasis/scedosporiosis of lung, bone, joint, CNS. Rare sites of involvement include sinusitis, keratitis, endophthalmitis, skin and soft tissue infections, prostatitis, and endocarditis.
Scedosporium prolificans usually causes localized infections in immunocompetent patients (bone and joint, eye, wounds, onychomycosis). In immunocompromised patients (e.g. neutropenia from chemotherapy), can disseminate and involve skin, lung, muscle, endophthalmitis
In immunocompetent hosts, includes keratitis, endophthalmitis, otitis, sinusitis, central nervous system infections, osteoarticular and soft tissue infections and pneumonia after near drowning
CNS disease may occur from contiguous spread from sinuses, penetrating trauma, or pulmonary infection from near-drowning
In immunosuppressed hosts, deep-seated infections can involve any organ with a predilection for skin, sinuses, lungs and central nervous system (typically following hematogenous dissemination)
In cystic fibrosis, can be colonizer and also cause infection
Diagnosis
With culture, though may represent colonization if recovered from a respiratory specimen
Microscopy
Both have septate, branching, hyaline hyphae with simple or branched annellide conidiophores, often annellide
May have Graphium state
The conidial states are morphologically indistinguishable
Species may be differentiated by physiological tests or by the presence of cleistothecia (for P. boydii)
Teleomorphs
Scedosporium boydii (teleomorphic state, Pseudallescheria boydii): Contains brown cleistothecia after 2-3 weeks of incubation that, when crushed, release ascospores
However, S. prolificans is extremely resistant to antifungals including amphotericin
Further Reading
ESCMID and ECMM joint guidelines on diagnosis and management of hyalohyphomycosis: Fusarium spp., Scedosporium spp. and others. Clin Micro Inf. 2014 20(Suppl 3):27-46. 10.1111/1469-0691.12465
