Association between inhaled antibiotic use and treatment-emergent organisms among Canadian people with cystic fibrosis.

Background: Inhaled antibiotics are frequently used as chronic Pseudomonas aeruginosa (Pa) suppressive therapy among people with cystic fibrosis (PwCF). However, their use might increase the risk of developing treatment-emergent respiratory organisms. This study aimed to describe the proportion of PwCF utilizing inhaled antibiotics, determine factors associated with inhaled antibiotic prescription, and determine if chronic inhaled antibiotic use is associated with an increased risk of Aspergillus fumigatus, Stenotrophomonas maltophilia, or Achromobacter spp.

Methods: This retrospective cohort study utilized Canadian CF Registry data. Pa status (chronic, intermittent, and negative) was defined per calendar year. The risk of developing A. fumigatus, S. maltophilia, or Achromobacter spp was compared between PwCF prescribed versus not prescribed inhaled antibiotics, adjusting for confounding by indication using inverse probability of treatment weighting.

Results: This analysis included data from 2800 PwCF. >75 % of PwCF with chronic Pa were prescribed inhaled antibiotics, while up to 13 % of PwCF negative for Pa received inhaled antibiotics during the study period. There was an increased risk of developing A. fumigatus among PwCF with intermittent Pa (HR 1.43, 95 %CI; 1.08-1.88; p = 0.01) and who were Pa negative (HR 2.44, 95 %CI; 1.65-3.61; p < 0.001), but not for PwCF with chronic Pa (HR 1.36, 95 %CI; 0.94-1.95; p = 0.10). No association was seen between inhaled antibiotics and developing either S. maltophilia or Achromobacter spp.

Conclusions: Inhaled antibiotic use among Canadian PwCF was associated with an increased risk of A. fumigatus acquisition but not S. maltophilia or Achromobacter spp. Prospective studies are needed to better define this association.