Objectives: To evaluate whether antistaphylococcal prophylaxis in infants and young children with cystic fibrosis (CF) would suppress the acquisition of Staphylococcus aureus and delay the onset of the manifestations of bronchopulmonary disease.
Study design: A 7-year, multicenter, double-blind, placebo-controlled study of continuous antistaphylococcal therapy. Otherwise healthy children <2 years of age with CF were randomly assigned to be treated with daily cephalexin (80-100 mg/kg/day) or placebo. Clinical, microbiologic, laboratory, radiographic, and anthropometric outcomes were evaluated.
Results: Of 209 children enrolled, 119 completed a 5- to 7-year course of therapy. Mean age at enrollment was 15.6 and 14.1 months in the cephalexin and placebo groups, respectively. Respiratory cultures from children treated with cephalexin were significantly less likely to be positive for S aureus (6.0% vs 30.4%; P <.001). They were, however, much more likely to be positive for Pseudomonas aeruginosa (25.6% vs 13.5%; P <.009). These differences became apparent in the first year after enrollment and persisted over the duration of the study. In contrast to these microbiologic differences, there were no differences in clinical outcome measures, including radiographic (Brasfield score, 23.4 vs 23.2) or anthropometric scores or pulmonary function.
Conclusions: Although long-term prophylaxis with cephalexin successfully delayed the acquisition of S aureus, it enhanced colonization with P aeruginosa and did not lead to clinically significant improvement in major health outcomes. These data do not support routine antistaphylococcal prophylaxisin otherwise healthy infants and young children with CF.