Activity of ceftazidime against Pseudomonas aeruginosa from bacteraemic and fibrocystic patients

Abstract

Minimum inhibitory and bactericidal levels of ceftazidime were determined for 337 isolates of Pseudomonas aeruginosa (135 mucoid, 202 non-mucoid) derived from fibrocystic patients, and 102 isolates of Ps. aeruginosa from blood or CSF. Fifty per cent of isolates of Pq. aeruginosa from all sources were inhibited by 2 mg/l of ceftazidime using inocula of 10(5)-10(6) colony forming units. Ninety per cent of the blood-culture and mucoid isolates were inhibited by 4 mg/l of ceftazidime, but more than 10 mg/l was required to inhibit 90% of the non-mucoid organisms. Bactericidal levels were close to the inhibitory levels. Of 30-isolates of Ps. cepacia, 50% were inhibited by 2 mg/l, and 90% by 4 mg/l of ceftazidime. Strains of pseudomonas derived from patients with fibrocystic disease were less susceptible than the strains from bacteraemic patients. Of the former, the mucoid strains were more susceptible than the non-mucoid strains. The patients with cystic fibrosis had been exposed to beta-lactam drugs for many years.