493 Bacterial and viral upper and lower airways infection in people with cystic fibrosis in stable condition

Background: Cystic fibrosis (CF) pulmonary exacerbations (PEx) significantly increase morbidity and mortality.Antibiotics are often changed during treatment of PEx in people with CF who have a poor clinical response.We aimed to characterize the reasons for antibiotic changes and examine the effects of these changes on lung function recovery.Methods: This was a retrospective cohort study using the Toronto CF database from 2009 to 2015 of adults and children with CF PEx treated with intravenous antibiotics.The primary outcome measure was absolute and relative change in forced expiratory lung volume in 1 second (FEV 1 ) at end of treatment and follow-up.Secondary outcome was the proportion of patients returning to more than 90% or more than 100% of baseline FEV 1 .Results: Of 399 PEx included, 105 had an antibiotic change.Reasons for antibiotic changes included change in antibiotic route before discharge (26%), drug reactions (20%), poor FEV 1 response (25%), and lack of symptom improvement (13%).In our multivariable analysis, of non-responders (<90% FEV 1 recovery to baseline or lack of symptom improvement at the interim time point), a change in antibiotics was not associated with any significant difference in absolute or relative FEV 1 at end of treatment or follow-up.Antibiotic change in non-responders was not associated with return to 90% or 100% baseline FEV 1 at end of treatment or follow-up.Conclusions: In this retrospective study using adult and pediatric PEx data from the Toronto CF database, we explored reasons for antibiotic changes and assessed the effects of changing antibiotics in patients with poor clinical response.Changing antibiotics during PEx treatment in people with CF with poor clinical response was not associated with better FEV 1 response or return to baseline lung function.