[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Gram-positive rods](https://durgical.com/en/microbiology/groups/gram-positive-rods/) › Nocardia

[Microbiology](https://durgical.com/en/microbiology/) · [Gram-positive rods](https://durgical.com/en/microbiology/groups/gram-positive-rods/)

# Nocardia

- Bacterium
- Gram-positive
- For completeness

A filamentous soil bacterium that causes lung infection and brain abscess in immunosuppressed people, and skin infection after wounds.

Updated 2026-11-01

Also called: Nocardia asteroides, Nocardia brasiliensis, Nocardia farcinica

## Key points

- Aerobic, branching and weakly acid-fast.
- Lung and brain in immunosuppressed people.
- Treated with sulfonamides.
- Unlike Actinomyces: anaerobic, not acid-fast, penicillin.

## At a glance

**Gram**
Gram-positive

**Shape**
Branching filaments that fragment

**Oxygen**
Obligate aerobe

**Family**
Nocardiaceae

**Stain**
Gram positive; weakly acid-fast (modified Kinyoun)

## Morphology

- Thin Gram-positive filaments branching at right angles
- Weakly acid-fast
- Slow growth in culture

## Transmission

- Inhaling soil dust
- Soil or water entering a wound
- Not considered contagious between people

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Virulence factors

- Mycolic acids in the cell wall
- Resists killing inside phagocytes
- Tendency to spread to the brain

## Diseases it causes

- Pulmonary, disseminated (brain abscess) and cutaneous nocardiosis; actinomycetoma (N. brasiliensis) [Nocardiosis →](https://durgical.com/en/conditions/nocardiosis/)

## Clinical picture

- Subacute pneumonia with nodules or cavities in a transplant recipient or a patient on corticosteroids
- Brain abscess
- Mycetoma: a swollen foot with sinus tracts and grains

## Diagnosis

- Gram stain: branching filaments
- Modified acid-fast stain (weakly positive)
- Prolonged culture and species identification with susceptibility testing
- Brain imaging in pulmonary disease

## Treatment

Sulfonamides (trimethoprim-sulfamethoxazole) are the mainstay, often combined with other antibiotics and given for months; some species such as N. farcinica are resistant, so susceptibility testing is needed. Abscesses may need drainage.

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

## Prevention

- Trimethoprim-sulfamethoxazole prophylaxis in some transplant recipients (it also prevents Pneumocystis)
- Protecting wounds from soil

## In Colombia

In Latin America, Colombia included, Nocardia brasiliensis is an important cause of actinomycetoma in rural workers who walk barefoot or are injured by thorns.

## Memory aid

Nocardia breathes air and takes the acid-fast stain halfway; its cousin Actinomyces chokes on oxygen and spits out yellow grains.

## Test yourself

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

## Which stain helps recognise Nocardia?

The modified acid-fast stain (modified Kinyoun): it is weakly positive.

## Which organ should be imaged in a patient with pulmonary nocardiosis?

The brain, because it is the most common site of spread.

## What is the mainstay of nocardiosis treatment?

Sulfonamides such as trimethoprim-sulfamethoxazole, guided by susceptibility testing.

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## Related

- [Actinomyces israelii](https://durgical.com/en/microbiology/actinomyces-israelii/)

## Related conditions

- [Nocardiosis](https://durgical.com/en/conditions/nocardiosis/)

## 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: Gram-positive rods](https://durgical.com/en/microbiology/groups/gram-positive-rods/)

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

Sources: [About Nocardiosis](https://www.cdc.gov/nocardiosis/about/index.html) (CDC, 2024); [Clinical Overview of Nocardiosis](https://www.cdc.gov/nocardiosis/hcp/clinical-overview/index.html) (CDC, 2024).

## **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.

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Source: https://durgical.com/en/microbiology/nocardia/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/nocardia/