The in-vitro activity of three anti-pseudomonal cephalosporins against isolates from patients with cystic fibrosis.

Minimal inhibitory concentrations (MICs) ofcefotaxime, cefsulodin and ceftazidime were determined for 50 isolates of Pseudomonas aeruginosa and 20 isolates of Staphylococcus aureus from 19 patients with cystic fibrosis (CF). These results were compared with the MICs of gentamicin and carbenicillin. Ceftazidime was the most active of the cephalosporins against Ps. aeruginosa, while cefotaxime was the most active against Staph. aureus. However, ceftazidime would appear to be the cephalosporin of choice for CF cases where both organisms are isolated. Ceftazidime was more active against the Ps. aeruginosa isolates than either gentamicin or carbenicillin. It was also active against strains of Ps. aeruginosa resistant to these antibiotics. In view of its good in-vitro activity against these isolates from CF patients, it is suggested that ceftazidime be considered for clinical trials in these patients.