[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Molds and dermatophytes](https://durgical.com/en/microbiology/groups/molds-and-dermatophytes/) › Mucorales (Rhizopus, Mucor)

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# Mucorales (Rhizopus, Mucor)

- Fungus
- Exam priority: medium

Soil molds that invade vessels and destroy tissue very fast, above all in diabetic ketoacidosis: from the sinuses into the orbit and brain.

Updated 2026-11-01

Also called: mucormycosis, zygomycosis, black fungus

## Key points

- Diabetic in ketoacidosis with a black eschar on palate or nose
- Broad ribbon-like hyphae, almost aseptate, at right angles
- Invades vessels: rapid necrosis
- Surgery plus lipid amphotericin B
- Voriconazole does not cover it; galactomannan negative
- Risk with deferoxamine and iron overload

## At a glance

**Shape**
Broad ribbon-like hyphae with few or no septa, branching at nearly right angles

**Family**
Mucoraceae and related families (Mucorales)

**Type**
Molds (filamentous fungi) of the order Mucorales

**Stain**
H&E, PAS and silver (GMS) on biopsy; calcofluor on direct exam

**Size**
Broad hyphae, about 6–25 µm

## Morphology

- Broad, irregular hyphae, flattened like a ribbon
- Almost no septa (pauciseptate)
- Branching at close to 90°
- In culture, very fast cotton-like growth with sporangia

## Transmission

- Inhaling spores from soil and decaying organic matter
- Inoculation into wounds, burns or trauma
- Rarely by ingestion
- Not spread from person to person

**Reservoir:** Soil, decaying plant matter, compost

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Virulence factors

- Invasion of blood vessels: thrombosis, infarction and black necrosis of tissue
- Exploits free iron: acidosis releases it from transferrin; deferoxamine acts as a siderophore for the fungus
- Thrives in acid, high-glucose conditions, which also impair neutrophils

## Diseases it causes

- Mucormycosis: rhinocerebral (the classic form in diabetes), pulmonary, cutaneous, gastrointestinal and disseminated
- Diabetic ketoacidosis: the main setting for rhinocerebral mucormycosis [Diabetic ketoacidosis →](https://durgical.com/en/conditions/diabetic-ketoacidosis/)

## Clinical picture

- Facial pain, nasal congestion with dark discharge and periorbital swelling in a decompensated diabetic
- Black eschar on the palate or turbinates
- Vision loss, ophthalmoplegia and cranial nerve palsies
- Very fast progression: hours to days

## Diagnosis

- Urgent biopsy: broad ribbon-like, sparsely septate hyphae invading vessels
- Tissue culture (may be negative even when hyphae are seen)
- CT or MRI of sinuses and orbit to map the extent
- Galactomannan and beta-D-glucan do not detect Mucorales

## Treatment

An emergency: wide surgical debridement, lipid amphotericin B as first line, and posaconazole or isavuconazole as alternatives or for step-down; correct the ketoacidosis and reduce immunosuppression. Voriconazole does not work against Mucorales.

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

In Pharmacology:

- [Amphotericin B](https://durgical.com/en/pharmacology/amphotericin-b/)
- [Posaconazole](https://durgical.com/en/pharmacology/posaconazole/)
- [Isavuconazole](https://durgical.com/en/pharmacology/isavuconazole/)

## Prevention

- Good diabetes control and prompt treatment of ketoacidosis
- Prudent corticosteroid use
- Care of wounds and burns contaminated with soil

## Memory aid

Mucor loves sweet, sour and iron: high sugar, ketoacidosis and free iron are its feast, and it leaves a black eschar where it eats.

## Test yourself

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

## Who is the typical patient with rhinocerebral mucormycosis?

A person with diabetes in ketoacidosis (also transplant, neutropenia or iron overload).

## What do Mucorales hyphae look like on biopsy?

Broad, ribbon-like, with few or no septa, branching at nearly right angles and invading vessels.

## Why does ketoacidosis favour mucormycosis?

Acidosis frees iron from transferrin, which the fungus uses to grow, and impairs neutrophil function.

## Which azole has no activity against Mucorales?

Voriconazole; posaconazole and isavuconazole are active.

## What are the two pillars of mucormycosis treatment?

Urgent surgical debridement and lipid amphotericin B, together with correcting the underlying disease.

[Add to my cards (5)](https://durgical.app/estudiar/?add=/en/microbiology/mucorales/)

## Related

- [Aspergillus fumigatus](https://durgical.com/en/microbiology/aspergillus-fumigatus/)

## Related conditions

- [Diabetic ketoacidosis](https://durgical.com/en/conditions/diabetic-ketoacidosis/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

[← Back to the group: Molds and dermatophytes](https://durgical.com/en/microbiology/groups/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: [Mucormycosis Basics](https://www.cdc.gov/mucormycosis/about/index.html) (CDC, 2024); [Mucormycosis Risk Factors](https://www.cdc.gov/mucormycosis/risk-factors/index.html) (CDC, 2024); [Clinical Overview of Mucormycosis](https://www.cdc.gov/mucormycosis/hcp/clinical-overview/index.html) (CDC, 2024).

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Representative model, for educational purposes only.

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