Rationale: Approval of aztreonam lysine for inhalation solution (AZLI) raised concerns that additional antibiotic exposure would potentially affect susceptibility profiles of Pseudomonas aeruginosa (PA) isolates from cystic fibrosis (CF) patients.Objective: This 5-year, prospective, observational study tracked susceptibility changes and clinical outcomes in CF patients in the United States with chronic PA infection.Methods: Sputum cultures were collected annually (2011-2016). The primary study endpoint was the proportion of subjects whose least susceptible PA isolate had an aztreonam minimum inhibitory concentration (MIC) that was >8 μg/mL (parenteral breakpoint) and increased ≥4-fold compared with the least susceptible isolate from the previous year. Annualized data for pulmonary exacerbations, hospitalizations, and FEV1% predicted were obtained from the CF Foundation Patient Registry and compared between subjects meeting/not meeting the primary endpoint.Results: 510 subjects were enrolled; 334 (65%) completed the study. A consistent proportion of evaluable subjects (13-22%) met the primary endpoint each year; and AZLI use during the previous 12 months was not associated with meeting the primary endpoint. While the annual decline in lung function was comparable for subjects meeting/not meeting the primary endpoint, more pulmonary exacerbations and hospitalizations were experienced by those who met it.Conclusions: Aztreonam susceptibility of PA remained consistent during the 5-year study. The relationship between PA isolate susceptibilities and clinical outcomes is complex; reduced susceptibility was not associated with accelerated decline in lung function, but was associated with more exacerbations and hospitalizations, likely reflecting increased overall antibiotic exposure.
120: A pediatric QI project to improve lung function and optimize treatment of CF pulmonary exacerbations
