Treatment of Mycobacterium fortuitum Peritonitis
For Mycobacterium fortuitum peritonitis, treatment should include catheter removal combined with at least two antibiotics based on in vitro susceptibility testing for a minimum of 4 months. 1
Diagnostic Considerations
- M. fortuitum is a rapidly growing, non-tuberculous mycobacterium (Runyon group IV) that can cause peritonitis in patients undergoing peritoneal dialysis 2
- Special culture techniques may be required for diagnosis, as standard bacterial cultures may be negative despite ongoing signs of infection 3
- Drug susceptibility testing is essential for guiding effective therapy, as resistance patterns vary 1
Treatment Algorithm
Initial Management:
- Catheter removal - Essential for successful treatment and should be performed promptly 2, 3, 4
- Drainage of any fluid collections or abscesses 3
- Initiate empiric antibiotic therapy pending susceptibility results:
- Combination of amikacin plus either cefoxitin or imipenem for at least 2 weeks or until clinical improvement 1
Antibiotic Selection Based on Susceptibility:
- M. fortuitum isolates are typically susceptible to multiple antibiotics 1:
- Amikacin (100% susceptibility)
- Ciprofloxacin/ofloxacin (100%)
- Sulfonamides (100%)
- Imipenem (100%)
- Cefoxitin (50%)
- Doxycycline (50%)
- Clarithromycin (80% - use with caution due to inducible resistance)
Treatment Duration:
- Minimum 4 months of combination therapy with at least two agents with in vitro activity 1
- Continue until resolution of infection and negative cultures 5
Special Considerations
Macrolide caution: Despite apparent in vitro susceptibility to clarithromycin in 80% of isolates, M. fortuitum contains an inducible erythromycin methylase erm(39) gene that confers resistance to macrolides. Therefore, macrolides should be used with caution and not as monotherapy 1
Surgical intervention: Surgery is generally indicated with extensive disease, abscess formation, or when drug therapy alone is insufficient 1, 6
Peritoneal damage: M. fortuitum peritonitis can cause significant peritoneal adhesions, potentially preventing future peritoneal dialysis 4
Monitoring response: Cultures typically become negative within six weeks of appropriate chemotherapy, except in cases of osteomyelitis which may take up to 14 weeks 5
Treatment Outcomes
With appropriate catheter removal and antibiotic therapy based on susceptibility testing, successful treatment rates of 90% have been reported for non-pulmonary M. fortuitum infections 5
Relapse is rare with adequate treatment duration, and development of drug resistance during therapy is uncommon 5
Patients may require conversion to hemodialysis if peritoneal adhesions prevent reinitiation of peritoneal dialysis 4