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Background: Published data suggest a lack of correlation between antimicrobial susceptibility testing (AST) of respiratory cultures and clinical outcomes in people with cystic fibrosis (CF). Nevertheless, AST is recommended by the CF Foundation (CFF) and the Cystic Fibrosis Trust. A survey of CF center program directors was conducted to understand how susceptibility testing is performed in North American CF centers. Methods: A survey was sent by the CFF to North American CF program directors and pharmacists via a CFF email distribution list. A reminder email was sent 2 weeks later. The survey was conducted using the online platform Survey Monkey, and responses were anonymous. Results: The survey of pharmacists is to be completed. The survey was completed by 36 of the 111 (32%) program directors who opened the email invitation. Two program directors provide care for fewer than 50 people with CF (6%),13 for 50 to 100 people (36%),10 for 100 to 200 people (28%), 4 for 200 to 300 people (11%), and 7 for more than 300 people (19%). In describing current AST practices, 3 CF centers (8%) had all susceptibility testing performed by a reference microbiology laboratory rather than an internal laboratory. AST methods included automated susceptibility testing (22, 67%), disk diffusion (17, 52%), and broth/microbroth dilution (14, 42%). Regarding frequency of obtaining respiratory cultures, 34 respondents reported obtaining respiratory cultures at each ambulatory care visit (94%), and 19 respondents obtained respiratory cultures during inpatient admission (53%). Thirty-three respondents (92%) reported obtaining identification and susceptibility testing for each respiratory culture collected. The remaining 3 respondents reported variable practices for susceptibility testing based on previous culture history. When asked about ideal AST practices, 21 respondents (58%) recommended susceptibility testing on every respiratory culture. If susceptibility testing was not performed on every culture, respondents recommended susceptibility testing at least once per year (8, 50%), each time a new isolate is identified (10, 63%), and as needed for a change in symptoms or clinical status during ambulatory care visits (8, 50%). Respondents reported using susceptibility data to inform clinical decisions, including initiation of antibiotic therapy for new isolates (30, 83%), initiation of antibiotics to treat pulmonary exacerbations (31, 86%), and for individuals with multidrug-resistant infections or a history of adverse drug reactions (31, 86%). Conclusion: The association between AST and clinical outcomes in CF is unclear, but most CF centers conduct routine susceptibility testing for each isolate as part of their standard of care. Almost half of program directors believed that AST was not needed for every culture. Finally, most program directors reported using AST data to inform clinical decisions. For these reasons, additional studies are needed to assess correlations more fully between ASTand clinical outcomes, and the cost-effectiveness of AST for all isolates should be assessed.


Medicine and Health Sciences


Presented at the North American Cystic Fibrosis Conference, November 2-5, 2021, Virtual.

Antimicrobial susceptibility testing practices at cystic fibrosis care centers