[Induction of beta-lactamases in Enterobacter cloacae with beta-lactam antibiotics]

The induction potency of various beta-lactam compounds was studied in a clinical isolate which exhibited resistance against most beta-lactam compounds; however, spontaneous beta-lactamase production was only marginal in this strain. In general, all beta-lactam derivatives included in this study possessed induction potency independent of the nucleus of the compound. N-formimidoyl thienamycin, the penem compound Sch 29482, 6-aminopenicillanic acid, and clavulanic acid proved to be the most potent inducers. With the exception of mezlocillin and ceftazidime there was a correlation between the concentration of the compound and the induction potency. Combination of two beta-lactam antibiotics resulted in an addition of the induction potency of each one. With respect to the considerable amount of enzyme that can be induced the development of resistance even against newer compounds fairly stable against the attack of beta-lactamases can be explained.