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Microbiology · Other fungi of clinical interest

Mycetoma agents !

  • Fungus
  • For completeness

A chronic infection of skin and bone, nearly always of the foot, that enters through a thorn. It forms lumps that drain pus with grains.

Updated 2026-11-01

Also called: Madura foot, maduromycosis

At a glance

Family
Eumycetoma: e.g. Madurella mycetomatis; actinomycetoma: Nocardia, Actinomadura, Streptomyces
Type
A syndrome, not one species: more than 70 agents, fungi (eumycetoma) or aerobic actinomycetes (actinomycetoma)
Stain
Grains: Gram (fine Gram-positive filaments in actinomycetoma), PAS or Grocott (broad hyphae in eumycetoma)
Size
Grains visible to the naked eye, coloured according to the agent

Morphology

  • Grain: a compact microcolony of the agent surrounded by inflammation; collected from the discharge or by biopsy.
  • Eumycetoma: grains with broad septate hyphae; those of Madurella mycetomatis are black from melanin.
  • Actinomycetoma: grains of very fine bacterial filaments; usually white or yellow, and red with Actinomadura pelletieri.

Transmission

  • Traumatic inoculation of contaminated soil or plant material (thorns, splinters, stones) into the skin.
  • Higher risk with walking barefoot and farm or manual work.
  • Not spread from person to person.

Reservoir: Soil, vegetation and water of dry tropical and subtropical areas

Isolation precautions

What the care team adds to standard precautions.

  • Standard

Virulence factors

  • Grains shield the agent from the immune system and from drugs.
  • Madurella melanin lowers azole activity in vitro.
  • Slow spread through tissue planes: skin, subcutis, muscle and bone, deforming the limb.

Diseases it causes

Clinical picture

  • A painless nodule that grows over months or years, with sinuses draining pus with grains.
  • Actinomycetoma reaches bone faster and is seen more often on the chest, abdomen or head.
  • Untreated, it leads to osteomyelitis, deformity and disability; sometimes amputation.

Diagnosis

  • Direct exam and staining of grains from aspiration or biopsy: tells fungus from bacterium, which decides treatment.
  • Culture of the grain (can misidentify species) and PCR, the most reliable but costly and poorly standardised.
  • Imaging (X-ray, MRI) to see bone extension.

Treatment

It depends on the agent: actinomycetoma responds to prolonged combined antibiotics (e.g. trimethoprim-sulfamethoxazole, amikacin) with good cure rates; eumycetoma needs azole antifungals (mainly itraconazole) and nearly always surgery, and relapses are common.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • Wearing shoes in endemic rural areas.
  • Early review of any chronic foot nodule: early diagnosis prevents disability.

Test yourself

Think of the answer, then tap the question to see it.

Why does it matter whether a mycetoma is eumycetoma or actinomycetoma?

Actinomycetoma is bacterial and is usually cured with antibiotics; eumycetoma is fungal, responds poorly to antifungals and nearly always needs surgery.

How does a person acquire mycetoma?

By inoculation of soil or plant debris into a small wound, such as a thorn while walking barefoot. It is not contagious.

What does a black grain in mycetoma discharge suggest?

Eumycetoma, typically from Madurella mycetomatis, whose pigment is melanin.

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Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: Mycetoma (WHO, 2022); Mycetoma Basics | Mycetoma | CDC (CDC, 2024).

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