Treatment of Mycobacterium gordonae Infection
In an immunocompromised patient with underlying lung disease and suspected M. gordonae infection, first confirm true pathogenicity through multiple positive cultures and strong clinical/radiological evidence before initiating treatment, as M. gordonae is almost always a contaminant; if true infection is confirmed, treat with a multidrug regimen including clarithromycin, ethambutol, and rifabutin based on in vitro susceptibilities. 1
Critical Diagnostic Considerations
Establishing True Pathogenicity vs. Contamination
- M. gordonae is the most frequently isolated mycobacterial contaminant and is almost always considered nonpathogenic 1
- The organism is readily recovered from freshwater, pipelines, and laboratory faucets, making contamination extremely common 1
- Multiple repeated positive cultures over months, along with strong clinical and radiological evidence of disease, are required to establish true infection with this low-pathogenicity organism 1
High-Risk Populations for True Infection
True M. gordonae infections occur primarily in patients with:
- AIDS or other immunosuppression 1
- Steroid therapy 1
- Carcinoma 1
- Peritoneal dialysis 1
- Transplant recipients 1
- Underlying lung disease (COPD, bronchiectasis) 2
Avoiding Contamination Pitfalls
- Patients should avoid rinsing or drinking tap water for several hours before collecting respiratory specimens to prevent false-positive cultures from tap water contamination 1
- Pseudo-outbreaks have been reported from contaminated tap water, ice, topical anesthetics, and bronchoscopy equipment 1
Treatment Regimen When True Infection is Confirmed
Antimicrobial Selection
The most consistently active agents in vitro include: 1
- Clarithromycin (or azithromycin)
- Ethambutol
- Rifabutin (or rifampin)
- Linezolid
- Fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin)
Recommended Treatment Approach
Multidrug combination therapy is essential: 3, 4, 5
- Three-drug regimen: Clarithromycin (or azithromycin) + Ethambutol + Rifabutin (or rifampin) based on susceptibility testing 3, 5, 2
- Alternative agents (fluoroquinolones, linezolid) can be added or substituted based on in vitro susceptibilities and patient tolerance 1, 5
Treatment Duration
- Minimum 12 months of therapy for pulmonary disease 3
- Continue treatment for at least 12 months with documented culture conversion 3, 4
- Some cases may require shorter courses (9 months) with good clinical response 6
Monitoring Response
- Sputum cultures should convert to negative within 2 months of appropriate therapy 6
- Serial chest imaging should demonstrate improvement or resolution of infiltrates 3, 5
- Follow-up cultures confirm microbiologic cure 2
Specific Clinical Scenarios
Disseminated Disease
- For disseminated M. gordonae (lung, bone marrow, other organs), use the same multidrug regimen with consideration for longer treatment duration 4
- Adequate source control is critical for therapeutic success 4
Skin and Soft Tissue Infections
- Multidrug antimicrobial therapy combined with adequate source control (surgical debridement if needed) 4
Immunocompetent Hosts
- Even in immunocompetent patients, true M. gordonae infection can occur and requires the same aggressive multidrug approach 3, 4, 5
- Do not dismiss as contaminant if multiple cultures are positive with compatible clinical/radiological findings 3
Key Clinical Pitfalls to Avoid
- Automatically dismissing M. gordonae as a contaminant without considering clinical context and repeat cultures 3, 2
- Initiating treatment without confirming true pathogenicity through multiple positive cultures and clinical correlation 1
- Using monotherapy or inadequate drug combinations, which will not achieve cure 4
- Failing to obtain susceptibility testing to guide optimal drug selection 1
- Premature discontinuation of therapy before achieving 12 months of treatment and documented culture conversion 3