[Effect of the induction of beta-lactamase synthesis in Pseudomonas aeruginosa strains on their resistance to penicillin]

Abstract

It was found that clinical strains of Ps. aeruginosa produced inducable beta-lactamase in the presence of penicillins, such as benzylpenicillin, ampicillin, carbenicillin. The amount of beta-lactamase depended on the strain and the inductor type and increased with the inductor concentration increase. Benzylpenicillin was the most active inductor of the enzyme synthesis by Ps. aeruginosa, strain 649. In concentrations of 5000 gamma/ml it provided at least 100 times higher amounts of beta-lactamase as compared to the initial level. The dynamics of induction of the enzyme synthesis by Ps. aeruginosa, strain 649 on addition of benzylpenicillin (5000 gamma/ml of the medium) at various stages of the culture growth was studied. Maximum accumulation of induced beta-lactamase was observed on addition of benzylpenicillin to the medium 2 hours after the culture inoculation. The induced enzyme was mainly found in the bacterialcells. The culture treatment with toluol increased the amounts of the determinable induced enzyme 4-26 times, 30 to 80 percent of the induced enzyme were liberated from the cells into the supernatant. Dependence of the level of the culture resistance to benzylpenicillin and ampicillin on the induction rate of beta-lactamase synthesis provided by the penicillins was found. No such dependence was observed with respect to the culture resistance to carbenicillin.