1989 Volume 37 Issue 12 Pages 1453-1457
In a previous study, we compared the induction rates of β-lactamase produced by cefoxitin in many Pseudomonas strains and found various induction rates among those tested. The inducibility was highest in Pseudomonas aeruginosa. In the present study, we investigated the induction in P. aeruginosa of β-lactamase by various antipseudomonal β-lactams and drug susceptibility after the induction.
Fifteen clinical isolates of P. aeruginosa were each treated with sub-inhibitory concentrations of 8 antipseudomonal β-lactams such as sulbenicillin, ticarcillin, piperacillin, cefsulodin, cefoperazone, cefpiramide, ceftazidime and aztreonam at 377deg;C for 2 hours to induce β-lactamase production. The βlactamase inducibility of these antibiotics differed among the test strains;β-lactamase activity was augmented sharply in the moderate β-lactamase producers after the induction. However, the enzyme activity of the constitutive and non-constitutive β-lactamase producers increased only slightly or not at all. On the other hand, the P. aeruginosa strains, which largely produced the β-lactamase after induction with these antibiotics, became resistant to them.
