What is the management of Mycobacterium chelonae infections?

Management of Mycobacterium chelonae Infections

The treatment of Mycobacterium chelonae infections requires combination antimicrobial therapy with clarithromycin as the cornerstone agent, along with at least one additional drug based on susceptibility testing to prevent resistance development. 1

Clinical Presentations

M. chelonae primarily causes:

• Skin, bone, and soft tissue infections (most common)
• Disseminated cutaneous disease (especially in immunocompromised patients)
• Keratitis (particularly after ocular surgery or contact lens use)
• Pulmonary disease (less common than M. abscessus)

Treatment Approach by Site of Infection

Skin, Soft Tissue, and Disseminated Disease

1. First-line regimen:

   • Clarithromycin 500 mg twice daily (100% susceptibility) 1
   • Plus at least one additional agent to prevent resistance development 1

2. Additional agents based on susceptibility:

   • Tobramycin (100% susceptibility, preferred over amikacin for M. chelonae) 1
   • Linezolid (90% susceptibility) 1
   • Imipenem (60% susceptibility, preferred over cefoxitin) 1
   • Amikacin (50% susceptibility) 1
   • Ciprofloxacin (20% susceptibility) 1

3. Duration of therapy:

   • For serious skin and soft tissue infections: minimum 4 months 1
   • For bone infections: 6 months 1

4. Surgical intervention:

   • Indicated for extensive disease, abscess formation, or when drug therapy is difficult 1
   • Removal of foreign bodies (e.g., breast implants, catheters) is essential for recovery 1

Wound Infections

1. Treatment approach:
   • Surgical debridement followed by antimicrobial therapy 1
   • Ciprofloxacin 750 mg orally twice daily plus an aminoglycoside or imipenem 1
   • Consider adding clarithromycin 500 mg twice daily 1

Corneal Infections

1. Treatment approach:
   • Combination of topical and oral agents 1
   • First-line agents include amikacin, fluoroquinolones, clarithromycin, and azithromycin 1
   • Drug selection based on susceptibility testing of the isolated organism 1
   • Note: Visual outcomes are often poor; many patients require corneal transplant 1

Pulmonary Disease

1. Treatment approach:
   • Clarithromycin plus a second agent based on susceptibility testing 1
   • Treatment duration should include 12 months of negative sputum cultures 1
   • If surgery is possible, it should be employed 1
   • Consider regimen of rifampicin (450-600 mg based on weight), ethambutol (15 mg/kg), and clarithromycin (500 mg twice daily) 1

Important Considerations

Antimicrobial Resistance

• Monotherapy with clarithromycin carries risk of resistance development (8% in one study) 1
• Recent reports indicate increasing antimicrobial resistance in M. chelonae 2
• Always use combination therapy to prevent resistance 1, 3

Treatment Duration

• If response to initial 6-month treatment is suboptimal, consider extending therapy up to 2 years 1
• For immunosuppressed patients, longer treatment courses may be necessary 4
• Treatment should continue until clinical resolution and negative cultures

Monitoring

• Regular clinical assessment for treatment response
• Follow-up cultures to document clearance
• Monitor for drug toxicities, particularly with long-term use of agents like linezolid
• Susceptibility testing should guide therapy adjustments if improvement is not seen

Special Populations

• Immunocompromised patients (especially those on corticosteroids) are at higher risk for disseminated disease 5
• Corticosteroid therapy is a significant risk factor for both localized and disseminated infections 5
• In patients who cannot discontinue immunosuppression, longer treatment courses may be necessary 4

Treatment Pitfalls

1. Monotherapy: Using clarithromycin alone can lead to rapid development of resistance 3

2. Inadequate duration: Short treatment courses often lead to relapse, especially in immunocompromised patients 4

3. Failure to remove foreign bodies: Persistent infection will occur if implants or catheters are not removed 1

4. Inappropriate drug selection: Using agents without confirmed susceptibility can lead to treatment failure 2

5. Delayed diagnosis: M. chelonae can be misdiagnosed as other bacterial infections, leading to inappropriate initial therapy