Methods: We conducted a nested case-control study of a retrospective cohort of adult LTR transplanted between 2007-2017. Cases were defined as LTR with nontuberculous mycobacterial (NTM) infections due to MAC and/or M. abscessus. Controls were defined as LTR without NTM infections. NTM infection was defined by presence of pulmonary symptoms and radiographic changes (clinical criteria) in addition to positive cultures from ≥2 sputa or ≥1 bronchial specimens (microbiological criteria) according to the IDSA/ATS criteria. LTR who meet microbiological, but not clinical criteria were considered colonized and not included for analysis. Azithromycin use was defined as ≥90 days for BOS treatment.
Results: Among 538 LTR, 60% (321/538) were male and 81% (434/538) received double LTs. Indication for LT was idiopathic pulmonary fibrosis (28% [152/538]), chronic obstructive pulmonary disease (23% [121/538]), cystic fibrosis [CF] (13% [68/538]) and other (37% [197/538]). The overall incidence of NTM infections was 4.3% (23/538); of which 65.2% (15/23), 17.4% (4/23) and 17.4% (4/23) were due to MAC, M. abscessus and polymicrobial infections respectively. 31% (165/538) of LTR received azithromycin. LTR who received azithromycin prophylaxis had 0.21 times the odds of developing NTM infections compared to LTR who did not receive azithromycin prophylaxis (OR: 0.21, 95% CI: 0.02 – 0.86, p = 0.02). Age (p=0.88), type of LT (p=0.81), pretransplant NTM colonization (p=0.46) and CF (p=0.22) were evaluated as possible risk factors, but were not associated with increased risk of developing NTM infections in bivariable analyses. In a multivariable logistic regression model, azithromycin prophylaxis was independently associated with decreased risk of NTM infections after adjusting for CF and pretransplant NTM colonization (aOR: 0.20, 95% CI: 0.05 – 0.88, p = 0.01).
Conclusion: Azithromycin use was associated with lower risk of NTM infections due to M. abscessus and MAC in our LTR.
S. Bennett, None
P. Chong, None