Three cases of infection with pulmonary Mycobacterium Avium complex with resistance to macrolides secondary to prolonged prior use for bronchectasis

Summary: The activity of atypical or non tuberculous mycobacteria (NTM) as pulmonary pathogens has been recognized even in immunocompetent individuals. The Mycobaterium avium complex (MAC) is the commonest of the 130 NTMs and comprises two species, M. avium and M. intracellulare. For the treatment of pulmonary MAC infection combination of a macrolide (azithromycin or clarithromycin) with rifampicin and ethambutol is required. An aminoglucoside (streptomycin or amikacin) should be added in cavitational or severe disease. The treatment is long and expensive, of uncertain efficacy and with serious adverse effects. One quarter of patients either fail to become culture negative or relapse despite treatment. In addition, only 52% of appropriately treated patients show clinical improvement. Resistance to macrolides is a significant negative prognostic factor. As in the case of antituberculosis drugs, the main mechanism of resistance development is prior exposure to monotherapy. Three cases are presented of MAC pulmonary infection with resistance to macrolides, which probably developed secondary to prolonged use for the treatment of exacerbations or maintenance therapy of bronchiectasis. Because of the increasing prevalence of NTM infection, the presence of nodules and bronchiectasis in a patient with pulmonary symptoms should raise the suspicion of NTM disease. The administration of macrolides without sufficient evidence poses the danger of development of resistance in the case of undiagnosed NTM disease, and testing for acid-fast bacilli is imperative before initiation of treatment of bronchiectasis with macrolides. Pneumon 2013,26(2