Azithromycin Not Tied to NTM Isolation in Bronchiectasis or COPD

Azithromycin exposure in the preceding year was not associated with incident respiratory nontuberculous mycobacterial (NTM) isolation in patients with non-cystic fibrosis bronchiectasis or COPD under a prespecified exposure definition, according to a nationwide Danish nested case-control study published online in CHEST.

Azithromycin reduces exacerbations in chronic airway disease, but whether it alters the risk of NTM isolation is unresolved, the investigators wrote. Because radiographic and clinical data were unavailable, the outcome was a first positive respiratory culture rather than NTM pulmonary disease.

The analyses included 173 case patients and 3,409 matched controls with bronchiectasis and 365 case patients and 7,300 controls with COPD. The prespecified exposure was at least 3,000mg of azithromycin with at least 2 prescriptions redeemed in the preceding 12 months, with a 3-month lag. Under this definition, azithromycin was not associated with NTM isolation in bronchiectasis (odds ratio [OR], 1.31; 95% CI, 0.79-2.18) or COPD (OR, 1.29; 95% CI, 0.78-2.13).

Under broader definitions, some associations emerged in COPD, including an OR of 1.61 (95% CI, 1.14-2.28) for 1 or more prescriptions, but estimates did not increase with cumulative exposure. The COPD association was concentrated within 90 days of the index date and attenuated as microbiological criteria became more stringent. In bronchiectasis, non-macrolide antibacterials were more strongly associated with NTM isolation than azithromycin at every matched threshold. The investigators said these patterns were more consistent with indication-driven testing than a drug effect, although in COPD an association with any azithromycin exposure persisted after accounting for other antibacterials.

Statistical resolution was limited, with 19 and 18 exposed case patients, and no records of negative cultures were available, so sampling frequency could not be compared. The authors said the data do not establish that azithromycin is safe with respect to NTM and cannot exclude a modest effect in either direction.

Source: Torsheim IL, Wedervang EB, Vognsen AK, et al. Azithromycin exposure and incident nontuberculous mycobacterial isolation in bronchiectasis and COPD: a nationwide nested case-control study. Chest. Published online October 28, 2026. doi:10.1016/j.chest.2026.10.016