Frequent microbiological surveillance during inpatient cystic fibrosis pulmonary exacerbations has limited clinical value.

Background: No evidence exists to guide the frequency of obtaining bacterial respiratory cultures during inpatient treatment of pediatric cystic fibrosis (CF) pulmonary exacerbations (PEx). At our institution, admission and weekly respiratory cultures are routinely collected to guide antimicrobial selection. This study evaluates the extent that this practice informs clinical management and the healthcare-related costs associated with routinely repeating cultures.

Methods: All children with CF with at least one hospital admission for IV antibiotics from January 2015 to December 2019 were included. Data collected included patient demographics, culture results, and antibiotic history. Respiratory cultures were numbered from the last clinic culture (`Culture 1'), culture on admission (`Culture 2'), and so on (`Cultures 3-6'). Outcomes assessed were microbiological results, frequency and timing of antibiotic change, and total microbiological laboratory costs.

Results: Seventy-eight children with 224 admissions and 695 bacterial cultures were analyzed. Repeated microbiology sampling revealed 118 new bacterial species in 82 admissions.  Culture 2 was most likely to identify a new bacterial species (91/115, 79.1 %) and most likely to be followed by a change in antibiotic (33/37; 89.2 %). The total cost of all cultures was $18,264.79. Eliminating Cultures 3-6 from routine practice could represent a 51 % cost-savings ($9,362.89), without significant impact on identification of new clinically relevant isolates.

Conclusion: Ongoing bacterial surveillance during a CF PEx beyond admission culture provides minimal information, rarely impacts clinical management, and can increase healthcare costs. An optimized approach would be to routinely obtain admission cultures and to obtain further cultures only if clinically indicated.