VanDevanter DR, Heltshe SL, Hilliard JB, et al. - Given that antimicrobial susceptibility testing (AST) of bacterial isolates is a time- and resource-intensive procedure recommended by cystic fibrosis (CF) treatment guidelines for antimicrobial selection for pulmonary exacerbation (PEx) treatment, researchers explored connections between Pseudomonas aeruginosa (Pa) isolate AST outcomes, antipseudomonal PEx treatments, and treatment responses as change in weight and percent predicted forced expiratory volume in 1 s (ppFEV ₁) as well as future antimicrobial treatment hazard for PEx occurring at a CF care center from 1999 through 2018. Of the 3,820 antimicrobial PEx treatment events in 413 individuals with Pa, 62.6% (2,390) had complete Pa coverage; 8.9% (340), 2.4% (99), and 26.2% (1000), had no, incomplete, and indeterminant Pa coverage, respectively. Superior responses for AST-defined complete Pa coverage treatments vs lesser coverage treatments were not observed, indicating that AST may be of little utility in choosing antimicrobials for CF PEx treatment.