From the Guidelines
Diagnosis of Mycobacterium avium complex (MAC) requires multiple tests including sputum cultures, bronchoscopy with bronchoalveolar lavage, chest imaging (CT scan), and sometimes lung biopsies, as recommended by the US Cystic Fibrosis Foundation and European Cystic Fibrosis Society consensus recommendations 1.
Diagnostic Tests
The diagnostic tests for MAC include:
- Sputum cultures, which should be performed annually in spontaneously expectorating individuals with a stable clinical course 1
- Bronchoscopy with bronchoalveolar lavage, which can be used to evaluate individuals with CF suspected to have NTM pulmonary disease 1
- Chest imaging (CT scan), which should be performed shortly before starting NTM treatment and at the end of NTM treatment to assess the radiological response 1
- Lung biopsies, which may be necessary in some cases, although transbronchial biopsies should not be routinely used to detect NTM in individuals with CF suspected to have NTM pulmonary disease 1
Treatment Options
The treatment options for MAC typically involve a three-drug regimen consisting of:
- A macrolide (clarithromycin 500-1000mg daily or azithromycin 250-500mg daily) 1
- Ethambutol (15mg/kg daily) 1
- Rifampin (600mg daily) 1 This combination therapy should continue for at least 12 months after culture conversion to negative, as recommended by the US Cystic Fibrosis Foundation and European Cystic Fibrosis Society consensus recommendations 1.
Additional Considerations
For severe or cavitary disease, adding amikacin or streptomycin injections for the first 2-3 months may be necessary, as recommended by the US Cystic Fibrosis Foundation and European Cystic Fibrosis Society consensus recommendations 1. Regular monitoring through sputum cultures every 1-2 months, liver function tests, visual acuity checks, and audiometry is essential to ensure treatment success and minimize potential side effects, including nausea, liver toxicity, vision changes, and hearing loss 1.
From the Research
Diagnostic Tests for Mycobacterium Avium Complex (MAC)
- The diagnosis of MAC lung disease is confirmed by multiple positive sputum culture findings in patients with typical symptoms and radiologic findings 2.
- Diagnosis requires 2 or more positive sputum cultures or 1 bronchoscopic specimen culture 3.
- MAC susceptibility is probably best tested using the radiometric method (BACTEC) 4.
- A complex of three proteins (Aro-Tal-AST) of molecular weight ~48 kDa can be used as a marker for simple and rapid ELISA based tests for differential diagnosis of M. avium infection in patients with M. avium complex (MAC) 5.
Treatment Options for Mycobacterium Avium Complex (MAC)
- Recommended treatment regimens include a macrolide and a rifamycin, but drug intolerance and relapse after treatment is completed often limit successful therapy 2.
- Treatment with a macrolide, ethambutol, and clofazimine was successful in 20 of 30 patients (67%) with MAC lung disease and is a reasonable alternative to rifamycin-containing regimens 2.
- The recommendation for those who are treated is a 3-drug regimen including macrolide, rifamycin, and ethambutol that is continued for 12 months beyond sputum culture conversion to negative 3.
- Intermittent azithromycin and ethambutol may be an optional treatment regimen for noncavitary MAC-PD 6.
- Amikacin liposome inhalation suspension is recommended for treatment-refractory patients whose cultures remain positive after 6 months of guideline-based therapy 3.
Challenges in Treating Mycobacterium Avium Complex (MAC)
- MAC-PD is difficult to treat, with frequent drug-related side effects and suboptimal treatment outcomes 3.
- Refractory and recurrent disease is common, leading to lifelong follow-up of patients 3.
- There are limited treatment options for patients with macrolide-resistant or refractory disease 3.
- Malabsorption of the oral antimycobacterial drugs is common, and patient-specific susceptibility data combined with therapeutic drug monitoring and dosage individualisation can help identify problems with drug therapy and overcome them 4.