Reduction of sputum Pseudomonas aeruginosa density by antibiotics improves lung function in cystic fibrosis more than do bronchodilators and chest physiotherapy alone.

We evaluated patients with cystic fibrosis (CF) and moderate obstructive lung disease in pulmonary exacerbation in a double-blind placebo-controlled trial to determine the contribution of antibiotic-mediated reduction in sputum bacterial density to clinical improvement. For the first 4 days of study, all patients received bronchodilating aerosols and chest physiotherapy but no antibiotics. During this time, the patients showed significant improvement in mean FVC, FEV1, and maximal midexpiratory flow rate (FEF25-75). In 12 of 13 trials, the patients showed no significant increases in the density of Pseudomonas aeruginosa during these first 4 days. In these 12 trials, the patients were stratified by their initial FVC and randomized to receive either parenteral tobramycin and ticarcillin (n = 7) or placebo (n = 5), in addition to continued aerosol and chest physiotherapy. In the remaining trial, the patient had a significant rise in the density of P. aeruginosa and was assigned to the antibiotic group. During the next 14 days of therapy, the antibiotic group showed significantly (p less than 0.01) greater reductions in log10 colony-forming units (cfu) of P. aeruginosa per gram of sputum and greater increases in FVC, FEV1, and FEF25-75 than did the placebo group. The degree of decrease in log10 cfu P. aeruginosa/g sputum correlated significantly (p less than 0.001) with the degree of improvement in FVC, FEV1, and FEF25-75.(ABSTRACT TRUNCATED AT 250 WORDS)