Mycobacterium abscessus pulmonary disease

Pulmonary disease caused by Mycobacterium abscessus is difficult to treat and of emerging importance, particularly in patients with cystic fibrosis. If M. abscessus is identified in sputum or bronchoscopic samples, close follow-up is required. Although patients may spontaneously clear M. abscessus, it should not be dismissed as a coloniser.

The M. abscessus complex can be further speciated into M. abscessus subspecies abscessus, M. abscessus subspecies bolletii, and M. abscessus subspecies massiliense. If possible, the subspecies should be determined because this can influence treatment choice—M. abscessus subsp. massiliense is more likely to be macrolide-susceptible, with higher rates of treatment success. Testing for inducible macrolide resistance should be done on all M. abscessus isolates by undertaking extended incubation of isolates in the presence of clarithromycin; inducible resistance may predict treatment failure.

The decision to treat can be complex and as with other nontuberculous mycobacteria will be guided by symptoms, progressive changes on CT scan, and recurrent isolation by culture. Cavitary disease suggests a high burden of infection and supports early treatment initiation.

There have been no clinical trials to guide drug selection, so recommendations are based on pharmacokinetic and pharmacodynamic studies, potential adverse effects, and the goals of therapy (eg to obtain microbiological cure, to target symptoms such as haemoptysis or cough). Patients often require multiple treatment courses.

Treatment consists of an initial phase followed by a continuation phase. The initial phase comprises a combination drug regimen; for example, oral azithromycin and clofazimine, plus intravenous amikacin and one or two other parenteral drugs such as cefoxitin, imipenem or tigecycline. The duration of the initial phase is 2 to 12 weeks, depending on the goals of therapy and tolerability of treatment. The continuation phase should include nebulised amikacin, oral azithromycin and clofazimine, and potentially other oral agents (eg linezolid, moxifloxacin, minocycline) based on susceptibility test results and tolerability. The duration of the continuation phase is usually at least 6 months, but may extend beyond 12 months. Seek expert advice.

In carefully selected patients with limited focal disease, surgical resection with perioperative combination drug therapy is often curative.

For detailed information on the management of M. abscessus pulmonary infections, see the British Thoracic Society Guidelines for the Management of Non-tuberculous Mycobacterial Pulmonary Disease (NTM-PD) [URL].