Specificity of beta-lactamase induction in Pseudomonas aeruginosa

The in-vivo induction of the chromosomally determined class Id beta-lactamase of Pseudomonas aeruginosa was studied in the granuloma pouch model in rats. Treatment of animals with carbenicillin, ticarcillin, piperacillin, azlocillin (100 mg/kg bd) and cefsulodin (40 mg/kg bd) resulted in Id beta-lactamase induction. beta-Lactamase induction was not only observed in those animals receiving beta-lactamase therapy, but also in the untreated control group, thus suggesting 'non specific' beta-lactamase induction by body fluids (such as serum or exudate). These findings agree with the observation that commercially available complex media such as Mueller Hinton Broth, IsoS-ensitest Broth, Brain Heart Infusion and Diagnostic Sensitivity Test broth, respectively, also exhibited induction potency. Further experiments revealed that aromatic amino acids as well as histidine largely contributed to the phenomenon of 'non specific' induction of Id beta-lactamase in Ps. aeruginosa.