Makindo Medical Notes

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

📖 About

• Nocardia species → cause nocardiosis, mainly in immunocompromised individuals.
• Environmental pathogen, not contagious between humans.

🔬 Characteristics

• Gram-positive, aerobic, non-spore-forming bacilli.
• Partially acid-fast → key distinguishing feature.
• Form filamentous branching structures, may fragment into rods (resembles fungi microscopically).

🏠 Source

• Soil-dwelling organism, infection via inhalation or traumatic inoculation.
• Main species:
  • N. asteroides → most pathogenic, pulmonary & disseminated disease.
  • N. brasiliensis → more cutaneous disease, esp. in South America.

⚠️ At-Risk Groups

• HIV/AIDS with CD4 <150/mm³.
• Chronic steroids / immunosuppressants.
• Solid organ & stem cell transplant recipients.
• Structural lung disease (bronchiectasis, CF, COPD).

🩺 Clinical Pathogenicity

• Pulmonary nocardiosis: Mimics TB → cavitating pneumonia, lung abscesses, necrosis (but non-contagious).
• Cutaneous nocardiosis: Post-trauma → nodules, cellulitis, ulceration.
• Disseminated nocardiosis: Haematogenous spread → brain abscesses 🧠, liver, kidneys.
• Ocular disease: Keratitis/endophthalmitis after trauma.

🧾 Clinical Features

• Fever, cough, dyspnoea (lung).
• Ulcers, abscesses (skin).
• Neurological: headache, seizures, confusion (brain abscess).
• Weight loss, malaise in disseminated infection.

🔎 Investigations

• Culture: Slow-growing (2–3 weeks) on blood agar.
• Microscopy: Filamentous, branching, weakly acid-fast organisms.
• Imaging: CT/MRI → cavitary lung lesions or brain abscesses.
• Biopsy/culture: Gold standard for confirmation.

💊 Management

• Antibiotics:
  • TMP-SMX = first line ✅.
  • Severe disease → combination with amikacin, imipenem, or 3rd-gen cephalosporin.
• Surgery: Drainage of abscesses (esp. brain/lung) may be needed.
• Duration: Prolonged therapy (6–12 months) due to relapse risk.
• Follow-up: Repeat imaging + cultures to monitor treatment response.

💡 Exam pearl: Think Nocardia in an immunocompromised patient with TB-like cavitary lung lesions + brain abscesses. Key clues: partially acid-fast, branching Gram-positive rods. Treatment = TMP-SMX long-term.