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.
Effect of pulmonary exacerbations treated with oral antibiotics on clinical outcomes in cystic fibrosis
