Effect of continuous antistaphylococcal therapy on the rate of P. aeruginosa acquisition in patients with cystic fibrosis.

SUMMARY. Continuous therapy with antistaphylococcal antibiotics is advocated by some cystic fibrosis (CF) centers, but it is unclear whether this strategy favors early colonization with P. aeruginosa. We used the data base for the German Centers of the European Registry for Cystic Fibrosis (ERCF) to assess the effect of continuous antistaphyloccocal therapy on the rate of P. aeruginosa acquisition in CF patients. Patients included in this analysis had to be < 18 years of age, P. aeruginosa-negative prior to entry in the ERCF, and to have had at least 2 additional P. aeruginosa-negative respiratory cultures while followed in the ERCF. Of the 639 patients fulfilling these criteria, 48.2% received continuous antistaphyloccocal therapy, 40.4% intermittent antibiotic therapy, and 11.4% no antibiotic therapy. There were no differences between the groups in body mass index, as well as forced vital capacity (FVC) and forced expired volume in 1 sec (FEV(1)) at baseline. The rate at which patients acquired positive respiratory cultures for Staph. aureus was significantly lower in the group receiving continuous antistaphyloccocal antibiotic therapy than in those not receiving such therapy. Patients receiving continuous antistaphyloccocal antibiotic therapy had a significantly higher rate of P. aeruginosa acquisition compared to patients receiving only intermittent or no antibiotic therapy. This difference was especially apparent for children younger than age 6 years. We conclude that continuous therapy with antistapyloccocal antibiotics directed against Staph. aureus increases the risk of colonization with P. aeruginosa. How this affects the clinical outcome of these patients remains to be determined.