Lung Disease Caused by Rapidly Growing Mycobacteria

Rapidly growing mycobacteria have only recently been recognized as pulmonary pathogens. When such organisms are recovered from respiratory secretions, well-defined diagnostic criteria suggested by the American Thoracic Society can be followed to determine the significance of a rapidly growing mycobacteria isolate. Mycobacterium abscessus is the rapidly growing mycobacteria species most frequently (82%) responsible for lung disease, followed by Mycobacterium fortuitum (13%). The typical patient is an elderly, nonsmoking woman with no known underlying lung disease. Some underlying conditions that are associated with rapidly growing mycobacterial lung disease include previous mycobacterial disease, gastroesophageal disorders with chronic vomiting, cystic fibrosis, and lipoid pneumonia. Human immunodeficiency virus infection is not an apparent risk, and the single largest group of patients are those with no underlying disorder. The chest radiograph typically shows bilateral noncavitary upper lung field infiltrates and may not be typical for pulmonary tuberculosis. With repeated isolation from the sputum of a rapidly growing mycobacteria species (especially Mycobacterium abscessus), more invasive diagnostic procedures, such as bronchoscopy, almost invariably confirm the diagnosis. Treatment is guided by in vitro susceptibilities. Mycobacterium fortuitum isolates are usually susceptible to oral antibiotic agents, whereas Mycobacterium abscessus isolates are susceptible only to parenteral agents and the newer macrolides (clarithromycin and azithromycin). Long-term cure is generally possible only with Mycobacterium fortuitum or localized disease due to Mycobacterium abscessus. Surgical resection is important for patients with lung disease caused by Mycobacterium abscessus.