Longitudinal development of initial, chronic and mucoid Pseudomonas aeruginosa infection in young children with cystic fibrosis

Background: While the emergence of chronic and mucoid Pseudomonas aeruginosa (Pa) infection are both associated with poorer outcomes among CF patients, their relationship is poorly understood. We examined the longitudinal relationship of incident, chronic and mucoid Pa in a contemporary, young CF cohort in the current era of Pa eradication therapy. Methods: This retrospective cohort was comprised of patients in the U.S. CF Foundation Patient Registry born 2006–2015, diagnosed before age 2, and with at least 3 respiratory cultures annually. Incidence and age-specific prevalence of Pa infection stages (initial and chronic [≥ 3 Pa + cultures in prior year]) and of mucoid Pa were summarized. Transition times and the interaction between Pa stage and acquisition of mucoid Pa were examined via Cox models. Results: Among the 5592 CF patients in the cohort followed to a mean age of 5.5 years, 64% (n = 3580) acquired Pa. Of those, 13% (n = 455) developed chronic Pa and 17% (n = 594) cultured mucoid Pa. Among those with mucoid Pa, 36% (211/594) had it on their first recorded Pa + culture, while mucoid Pa emerged at or after entering the chronic stage in 12% (73/594). Mucoidy was associated with significantly increased risk of transition to chronic Pa infection (HR = 2.59, 95% CI 2.11, 3.19). Conclusions: Two-thirds of early-diagnosed young children with CF acquired Pa during a median 5.6 years of follow up, among whom 13% developed chronic Pa and 17% acquired mucoid Pa. Contrary to our hypothesis, 87% of young children who developed mucoid Pa did so before becoming chronically infected.