Makindo Medical Notes

Related Subjects: | Pasteurella Multocida | Capnocytophaga canimorsus | Snake Bites | Dog Bites | Tetanus | Pasteurella multocida

About

• Nocardia species cause nocardiosis, a bacterial infection that primarily affects immunocompromised individuals.

Characteristics

• Gram-positive, aerobic, non-spore-forming bacteria.
• Partially acid-fast, forming filamentous structures that can fragment into rods.

Source

• Nocardia species are commonly found in soil, and transmission occurs via airborne particles (inhalation).
• Two main species cause similar diseases:
  • Nocardia asteroids: The most pathogenic and frequently encountered species.
  • Nocardia brasiliensis: More commonly seen in South America.

Immunocompromised Individuals at Risk

• CD4+ counts < 150/mm³ (especially in HIV/AIDS patients).
• Individuals on chronic steroid therapy.
• Solid organ transplant recipients.
• Stem cell transplantation patients.
• People with structural lung diseases such as bronchiectasis, cystic fibrosis, or severe COPD.

Clinical Pathogenicity

• Pulmonary nocardiosis: Often mimics tuberculosis (TB) but is not contagious. Can result in lung abscesses, pneumonia, cavitary lesions, and necrosis.
• Cutaneous/subcutaneous nocardiosis: Occurs due to traumatic implantation, leading to localized skin infections, nodules, or ulcers.
• Disseminated nocardiosis: In immunocompromised individuals, *Nocardia* can spread haematogenously, causing abscesses in multiple organs, including the brain, liver, and kidneys. Brain abscesses are a common severe manifestation.
• Ocular nocardiosis: Can result in keratitis or endophthalmitis, typically following trauma to the eye.

Clinical Manifestations

• Fever, cough, and difficulty breathing (in pulmonary cases).
• Skin ulcers, abscesses, or cellulitis (in cutaneous cases).
• Neurological symptoms such as headache, confusion, or seizures (if brain abscesses are present).
• Fatigue, weight loss, and general malaise in disseminated infections.

Investigations

• Nocardia grows well on blood agar but may take 2–3 weeks for colonies to appear.
• Microscopy can show filamentous, partially acid-fast organisms in tissue samples or respiratory secretions.
• Imaging (CT or MRI) to assess the presence of lung abscesses or brain lesions.
• Biopsy or culture of affected tissue for definitive diagnosis.

Management

• Antibiotics: Long-term antibiotic therapy is required due to the slow-growing nature of *Nocardia*.
  • Trimethoprim-sulfamethoxazole (TMP-SMX) is the first-line treatment.
  • In severe cases, combination therapy with amikacin, imipenem, or a third-generation cephalosporin may be necessary.
• Surgical Intervention: In cases of abscesses, especially in the brain or lungs, surgical drainage may be required in addition to antibiotic therapy.
• Duration of Treatment: Therapy typically lasts 6–12 months due to the high recurrence rate of nocardiosis.
• Regular follow-ups with imaging and microbiological tests are necessary to monitor the response to treatment and prevent relapse.