1107. Three Year Longitudinal Assessment of Pseudomonas aeruginosa (Pa) Antibiotic Susceptibility in Children with Cystic Fibrosis (CF) in the Era of Modulator Therapy

BACKGROUND: CF is a genetic disease characterized by chronic lung infection, often with Pseudomonas aeruginosa (Pa). It is widely accepted that increasing antibiotic resistance develops in Pa following repeated antibiotic exposure. With the advent of elexacaftor/tezacaftor/ivacaftor (ETI) modulator therapy, we wished to assess Pa antibiotic resistance to beta-lactam and fluoroquinolone (FQ) antibiotics in both children receiving ETI, and those not eligible for ETI (nonETI) who continue to experience recurrent pulmonary exacerbation (PEx) and require repeated antibiotic treatment. METHODS: We examined current patterns of antibiotic resistance over 3 years for a cohort of 11 children with CF having 5 or more positive sputum cultures for Pa between January 2020-December 2022 obtained from CF clinic and hospital PEx sputum samples. Chart review included: demographic data; dates of PEx/hospitalization; dates of CF clinic visits; dates and results of CF sputum cultures; and antibiotics used and dates for intravenous (IV) and oral (PO) treatment courses. RESULTS: Six males and 5 females were reviewed (6/11 [54%] were Hispanic), with 3/11 (27%) on ETI therapy (average age 14.6 yr), and 8/11 (73%) not on ETI therapy (average age 11.6 yr). Average age at acquisition of Pa was 10.2 yrs. The average number of cultures yielding Pa over 3 years was 11 for both ETI and nonETI subjects. Average number of IV antibiotic courses was 6 for nonETI, but 0 for ETI subjects, while the average number of oral (PO) FQ courses with ciprofloxacin/levofloxacin was 6 in nonETI, and only 1 in ETI subjects. No increase in antibiotic resistance was noted against any IV antibiotic over 3 years of observation (Table), but of the 9 subjects (both ETI and nonETI) who received PO FQ, 5 (55%) were documented to have at least one nonsusceptible isolate, as shown for one 16 year old nonETI subject (Figure). [Figure: see text] [Figure: see text] CONCLUSION: Current antibiotic/pulmonary management of children with CF was not associated with an increased risk of IV antibiotic resistance over 3 years of observation despite repeated exposure for PEx (mean of 6 IV antibiotic courses per nonETI subject), but susceptibility to FQ decreased in 55% of those treated over 3 years following repeated FQ oral therapy courses. DISCLOSURES: All Authors: No reported disclosures