Specificity of β-lactamase induction in Pseudomonas aeruginosa

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Abstract
The in-vivo induction of the chromosomally determined class Id β-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 β-lactamase induction. β-Lactamase induction was not only observed in those animals receiving β-lactamase therapy, but also in the untreated control group, thus suggesting ‘non specific’ β-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 β-lactamase in Ps. aeruginosa.