Scedosporium

Background

Microbiology

• Septate hyaline mold
• Macroscopic appearance
  • 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
  • Scedosporium apiospermum (teleomorphic state, Pseudallescheria apiosperma)

Management

• S. apiopsermum is treated with voriconazole or amphotericin B
• 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