Clinical Outcomes of Antipseudomonal versus Other Antibiotics among Children with Cystic Fibrosis without Pseudomonas aeruginosa .

Rationale: Antibiotic selection for pulmonary exacerbation (PEx) management in children with cystic fibrosis is typically guided by prior respiratory culture results. Although antipseudomonal antibiotics are often used in children with chronic Pseudomonas aeruginosa (Pa) airway infection, no data exist to guide antibiotic selection in children who are culture negative for Pa for ≥1 year. Objectives: To determine among children classified as 1, 2, or 3 years' Pa negative if PEx treatment with at least one oral and/or intravenous antipseudomonal antibiotic is associated with improved clinical outcomes compared with treatment with antibiotics not effective against Pa. Methods: A retrospective cohort study was conducted using the linked Cystic Fibrosis Foundation Patient Registry-Pediatric Health Information System database. We included children 6-21 years old hospitalized between 2008 and 2018 consistently culture negative for Pa 1 year before a study PEx. Children were classified as 1 or 2 years' Pa negative if their last Pa-positive culture occurred in the 13-24 months or 25-36 months before a study PEx, respectively, with all subsequent cultures negative for Pa. Children classified as 3 years' Pa negative had no Pa-positive cultures in the 36 months before a study PEx. Inverse probability of treatment weighted linear or logistic regression models were used to compare clinical outcomes (pre- to post-PEx forced expiratory volume in 1 s, odds of returning to ≥90% of baseline lung function, and odds of having a future PEx) between antipseudomonal and non-antipseudomonal antibiotic strategies. Results: Among all children included in the linked data set, 1,290 children with 2,347 PExs were eligible for analysis. Among all study PExs, 530, 326, and 1,491 were classified as 1, 2, and 3 years' Pa negative, respectively, and antipseudomonal antibiotics were administered in 79%, 67%, and 66% of all PExs classified as 1, 2, and 3 years' Pa negative, respectively. For all Pa-negative groups, when compared with non-antipseudomonal antibiotic regimens, antipseudomonal antibiotic treatment was not associated with greater improvement in any studied clinical outcome. Conclusions: Despite their common use, including antibiotics effective against Pa may provide no additional benefit for PEx treatment among children who are Pa negative for at least 1 year prior. Prospective trials are warranted to directly test this hypothesis.