Azithromycin and nontuberculous mycobacteria: Is there an association?
Nontuberculous mycobacteria (NTM) infection can complicate a number of chronic respiratory conditions. Eradication of these organisms can be difficult, requiring prolonged course (up to 2 years) of multiple antibiotics. Azithromycin (AZM) is often used for its immunomodulatory effects to help reduce the frequency and severity of respiratory infections in patients with chronic respiratory conditions (e.g. bronchiectasis). Studies in the cystic fibrosis (CF) population have identified a possible link between long term AZM use and risk of NTM infection, though few studies have researched whether there is a similar link in non-CF populations. The aim of this study was to establish whether there is an association between the use of AZM and NTM detection in the non-CF population. Retrospective data for 118 patients with positive cultures for NTM between May 2011 and November 2015 in Royal Derby Hospital were collected using electronic lab results and clinic letters. These were analysed to establish the species of mycobacterium cultured, underlying respiratory diagnosis and if AZM was prescribed. The data showed that the 3 commonest NTM found were M.intracellulare and M.avium at equal incidence of 25.4%, followed by M.gordonaae (11.9%). Patients with bronchiectasis (49.2%) and COPD (38.1%) were more likely to have positive cultures for NTM. AZM was prescribed for varying course lengths in 16.1%. Of those, 52.6% had been on AZM prior to the NTM detection and 31.5% were on long term prophylaxis. The findings of this study suggests that NTM detection in patients with underlying non-CF respiratory conditions may not be related to AZM use, though further research is required to investigate the strength of this link.
- Specialist Medicine 
Van Heeswijk, Isabelle