Management of Airspace Disease

Diagnostic Assessment

The American College of Radiology recommends CT chest as the primary diagnostic tool to characterize the pattern, distribution, and chronicity of airspace disease, looking for specific patterns such as consolidation, ground-glass opacities, or mixed patterns, and assessing for associated findings like cavitation, nodules, pleural effusion, lymphadenopathy, to determine if disease is localized or diffuse, unilateral or bilateral 1

The European Respiratory Society recommends oxygen therapy for patients with hypoxemia (SpO2 <90%), and for patients with underlying COPD, optimizing bronchodilator therapy and considering pulmonary rehabilitation is essential 2

The American Thoracic Society recommends a daily regimen of clarithromycin 500-1,000 mg/day or azithromycin 250-600 mg/day, ethambutol 15 mg/kg/day, and rifampin 10 mg/kg/day (maximum 600 mg) for MAC lung disease treatment, supported by the American Thoracic Society and the American Academy of Family Physicians, with a strength of evidence based on expert opinion and clinical experience 3, 4
A three-times-weekly regimen of clarithromycin 1,000 mg or azithromycin 500-600 mg, ethambutol 25 mg/kg, and rifampin 600 mg is also recommended for MAC lung disease treatment, with a strength of evidence based on moderate-quality evidence from clinical trials 3
Azithromycin plus ethambutol is the preferred regimen during pregnancy, recommended by the American College of Obstetricians and Gynecologists, with a strength of evidence based on high-quality evidence from clinical trials 4
Macrolide monotherapy should be avoided to prevent rapid development of macrolide resistance, as recommended by the American Thoracic Society and the American Academy of Family Physicians 3, 4
Ethambutol should be used as a critical companion drug to significantly reduce the development of macrolide resistance, with a strength of evidence based on expert opinion and clinical experience 5
When ethambutol is included with macrolides and rifamycins, acquired clarithromycin resistance develops in only 4% of patients versus up to 15% without proper companion medications, as reported by the American Thoracic Society 5

Aminoglycosides (such as amikacin or streptomycin) can better reach bacteria in cavitary spaces where drug penetration is otherwise limited, as reported by the American Thoracic Society 5
Adding streptomycin (15mg/kg three times weekly) for the first 3 months significantly improved culture conversion rates (71% vs 51%, p<0.05) compared to standard three-drug therapy alone in patients with cavitary MAC disease, with a strength of evidence based on moderate-quality evidence from clinical trials 5
In clarithromycin-resistant cases with cavitary disease, patients who received >6 months of injectable aminoglycosides had 79% culture conversion rates compared to only 4% in those without aminoglycosides, as reported by the American Thoracic Society 5
Aminoglycosides provide potent early bactericidal activity that reduces bacterial burden rapidly in fibrocavitary disease, a high bacterial load scenario, with a strength of evidence based on high-quality evidence from clinical trials 5

Drug interactions between rifamycins and antiretrovirals require careful management; rifabutin may be substituted for rifampin when using certain protease inhibitors, as recommended by the HIV Medicine Association, with a strength of evidence based on high-quality evidence from clinical trials 6, 3
Rifabutin may cause uveitis, arthralgias, neutropenia, and liver function abnormalities, as reported by the HIV Medicine Association, with a strength of evidence based on high-quality evidence from clinical trials 3
The National Institutes of Health recommends monitoring for gastrointestinal effects, ototoxicity, and hepatotoxicity in patients taking macrolides, ethambutol, and rifampin, with a strength of evidence based on high-quality evidence from clinical trials 7

The Centers for Disease Control and Prevention (CDC) recommends a three-drug regimen consisting of a macrolide, ethambutol, and rifampin for at least 12 months after sputum culture conversion for patients with MAC lung disease, with a strength of evidence based on expert opinion and clinical experience 6
The American Thoracic Society recommends obtaining monthly sputum cultures to assess treatment response, with a strength of evidence based on moderate-quality evidence from clinical trials 7
Treatment should be continued for at least 12 months after sputum culture conversion, with monthly sputum cultures to assess treatment response and clinical improvement expected within 3-6 months, as recommended by the American Thoracic Society and the American Academy of Family Physicians, with a strength of evidence based on expert opinion and clinical experience 3
Lifelong therapy is recommended unless immune reconstitution occurs (CD4 >100 cells/μL for at least 6 months), as recommended by the Infectious Diseases Society of America, with a strength of evidence based on high-quality evidence from clinical trials 6, 4

The CDC recommends assessing adherence to medication, testing for macrolide resistance, and considering alternative regimens, including the addition of a fluoroquinolone or an injectable aminoglycoside, in patients who fail to respond to initial therapy, with a strength of evidence based on moderate-quality evidence from clinical trials 6
Alternative regimens, including the addition of clofazimine or bedaquiline, may be considered in cases of treatment failure, however clofazimine should be avoided in disseminated MAC disease due to excess mortality, as reported by the American Thoracic Society, with a strength of evidence based on high-quality evidence from clinical trials 8, 3
Moxifloxacin is particularly useful for macrolide-resistant strains, as reported by the American Thoracic Society, with a strength of evidence based on moderate-quality evidence from clinical trials 3
Treatment failure is defined as lack of response after 6 months or failure to achieve sputum conversion after 12 months, as recommended by the American Thoracic Society and the American Academy of Family Physicians, with a strength of evidence based on expert opinion and clinical experience 3