Treatment of lower respiratory tract infections due to Pseudomonas aeruginosa in patients with cystic fibrosis.

Twelve patients who underwent 26 episodes of lower respiratory tract infection due to Pseudomonas aeruginosa were treated with aztreonam. Infectious episodes were severe in 11 patients, moderate in 10 patients, and mild in five patients. In 85% of the episodes, significant clinical improvement occurred, but in four severe episodes, the clinical response was unsatisfactory. The mean interval between initiation of treatment and improvement was seven days. Aztreonam was as clinically effective in the treatment of infections due to organisms susceptible to penicillins active against Pseudomonas as it was in the treatment of infections due to organisms resistant to these agents. P. aeruginosa was not permanently eradicated from the sputum of any of the patients treated with aztreonam. It did not cause any major adverse effects, and the only laboratory abnormality found was an increase in alkaline phosphatase, which occurred during 12 (46%) courses of therapy. Levels of alkaline phosphatase returned to normal after conclusion of treatment. Aztreonam was shown to be clinically effective in the treatment of lower respiratory infections due to P. aeruginosa in patients with cystic fibrosis.