Differences in drug susceptibility between isolates of pseudomonas cepacia recovered from patients with cystic fibrosis and other sources and its relationship to beta‐lactamase focusing pattern

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Abstract
Pseudomonas cepacia, a significant pulmonary pathogen among children with cystic fibrosis (CF), often possesses an inducible β‐lactamase. The β‐lactamase isoelectric focusing pattern and β‐lactam susceptibility of CF and non‐CF isolates of P. cepacia were compared. Against all of the test strains, ceftazidime and piperacillin were more effective than aztreonam. More CF isolates were resistant to 8 μg/ml of ceftazidime than non‐CF isolates. Isoelectric focusing of cefoxitin‐induced, cell‐free preparations of the CF isolates produced significantly more bands than comparable preparations of non‐CF isolates. Organisms producing a β‐lactamase band that focused in the pH range of 8.5 to 8.7 were significantly more resistant to 8 μg/ml of ceftazidime than other isolates. The increased resistance of CF isolates of P. cepacia to ceftazidime may be the result of the production of a specific bacterial β‐lactamase.