Fusarium

Background

Microbiology

• Macroscopic: colonies grow rapidly with wooly texture (sometimes mucoid), and white, yellow, pink, purple, or pale brown surface and pale, red, violet, brown, or blue reverse.
• Microscopic: septate hyaline hyphae. Microconidia are unicellular (sometimes bicellular) and hyaline, ovoid to ellipsoid, in chains or singly from denticles. Macroconidia are curved and multicellular, with a foot cell at the base. Chlamydospores may be present.
  • The macroconidia are the typical finding used to identify Fusarium spp.
• Species of medical importance include:
  • F. solani: most common overall, and a common cause of keratitis
  • F. oxysporum: second-most common
  • F. verticillioides: third-most common
  • F. moniliforme
  • F. proliferatum
  • F. chlamydosporum
  • F. anthophilum
  • F. dimerum
  • F. sacchari

Epidemiology

• Ubiquitous, common in soil and organic debris, and a common cause of disease in plants.
• In humans, infection is rare and generally occurs after penetrating trauma.
• Disseminated and CNS disease is more common in immunocompromised hosts, including prolonged neutropenia.

Clinical Manifestations

• Superficial
  • Keratitis and endophthalmitis: big outbreak associated with contact lens solution back in the day
  • Onychomycosis
  • Skin and musculoskeletal infections (including mycetoma)
• Locally invasive
  • Pneumonia
  • Peritonitis associated with peritoneal dialysis
  • Brain abscess
• Disseminated infection
  • Fungemia: can be detected in blood culture
  • Disseminated infection

Management

• Remove indwelling lines, if possble
• Treat underlying immunocompromise, if possible
• Amphotericin B (high dose) is the antifungal of choice, although voriconazole and posaconazole have also been used
• Some species are inherently resistant to amphotericin, so may need to treat with combination amphotericin and voriconazole until susceptibilities are available