Fusarium and Scedosporium
- Fungus
- Exam priority: medium
Clear (non-pigmented) environmental molds that cause eye infections after trauma or contact lenses and deadly infections in neutropenic patients.
Also called: fusariosis, Scedosporium apiospermum, Lomentospora prolificans, hyalohyphomycosis
Quick facts
- Type
- Fungus · Molds and dermatophytes
- Gram / shape
- Thin septate hyphae with acute-angle branching
- Spread
- Corneal trauma with plant material
- Causes
- Fungal keratitis · Disseminated fusariosis
- Treatment
- Fusarium
At a glance
- Shape
- Thin septate hyphae with acute-angle branching in tissue, like Aspergillus; Fusarium makes banana-shaped macroconidia in culture
- Family
- Fusarium: Nectriaceae; Scedosporium and Lomentospora: Microascaceae
- Type
- Hyaline (non-pigmented) filamentous molds
- Stain
- KOH, calcofluor white, GMS or PAS; culture needed to tell them from Aspergillus
Morphology
- Fusarium: in culture, cottony colonies, often pink to violet, with curved multicellular (banana-shaped) macroconidia.
- Scedosporium apiospermum: gray-white colonies with oval single-celled conidia.
- In tissue all look like Aspergillus: hyaline septate hyphae that invade blood vessels.
Transmission
- Corneal trauma with plant material, or contamination of contact lenses and lens cases (keratitis).
- Inhalation of conidia from air, soil or hospital water (sinuses and lungs).
- Entry through damaged skin or nails (onychomycosis is a common door for disseminated fusariosis); aspiration of polluted water in near-drowning (Scedosporium).
Reservoir: Soil, plants and water, including hospital water systems and shower heads (Fusarium); Soil, sewage and polluted water (Scedosporium)
Isolation precautions
What the care team adds to standard precautions.
- Standard
Virulence factors
- Angioinvasion with thrombosis and tissue necrosis, as in aspergillosis.
- Fusarium sporulates inside tissue (adventitious sporulation), so blood cultures are often positive.
- High intrinsic resistance to many antifungals: Fusarium resists echinocandins and fluconazole; Lomentospora prolificans resists almost all drugs.
Diseases it causes
- Fungal keratitis: Fusarium is a leading cause after plant trauma or contact lens use. Keratitis and corneal ulcer →
- Disseminated fusariosis in prolonged neutropenia or after stem cell transplant: fever, painful necrotic skin nodules, lung lesions, positive blood cultures. Febrile neutropenia →
- Scedosporium: eumycetoma after trauma, pneumonia and brain abscess after near-drowning, and airway colonization in cystic fibrosis. Mycetoma (actinomycetoma and eumycetoma) →
Clinical picture
- Keratitis: pain, red eye and a feathery-edged corneal infiltrate, sometimes with hypopyon.
- Neutropenic fusariosis: many painful red papules or nodules with central necrosis on the limbs, often starting from an infected toenail.
- Scedosporium is one of the molds most often isolated from respiratory secretions in cystic fibrosis.
Diagnosis
- Corneal scrapings: KOH or calcofluor and culture.
- Deep skin biopsy with histology and culture in disseminated disease; blood cultures are often positive in fusariosis, unlike aspergillosis.
- Galactomannan may be positive; beta-D-glucan helps more to rule out than to confirm.
- Species identification by molecular methods or mass spectrometry is important because susceptibility differs.
Treatment
Fusarium: voriconazole or lipid amphotericin B, sometimes combined, plus surgical debridement; topical antifungals (natamycin, voriconazole) for keratitis. Scedosporium apiospermum: voriconazole first. Lomentospora prolificans is resistant to most antifungals. Recovery of neutrophils largely decides survival.
Drug class only; doses and regimens are set by the clinician from the current guideline.
In Pharmacology:
Prevention
- Correct contact lens hygiene: never tap water, change the case, do not sleep or swim with lenses.
- Looking for and treating onychomycosis and skin breaks before chemotherapy.
- Mold-active prophylaxis and water and air control in hematology units.
Test yourself
Think of the answer, then tap the question to see it.
Which mold is a leading cause of fungal keratitis after plant trauma or contact lens use?
Fusarium.
Why are blood cultures often positive in fusariosis but not in aspergillosis?
Fusarium produces spores inside tissue (adventitious sporulation) that are released into the blood.
What skin finding suggests disseminated fusariosis in a neutropenic patient?
Multiple painful red papules or nodules with central necrosis, often with a toenail infection as the entry point.
Which setting is classic for Scedosporium apiospermum infection in a healthy person?
Near-drowning in polluted water, followed by pneumonia and brain abscess.
Connections
← Back to the group: Molds and dermatophytes
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Invasive fusariosis (Clinical Microbiology Reviews (PMC), 2023); Infections Caused by Scedosporium spp. (Clinical Microbiology Reviews (PMC), 2008); Rare fungal infectious agents: a lurking enemy (F1000Research (PMC), 2017).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.