Physiological studies of the regulation of beta-lactamase expression in Pseudomonas maltophilia.
The kinetics of beta-lactamase induction in Pseudomonas maltophilia IID1275/873 were investigated. Upon induction with beta-lactam antibiotics, a correlation was seen between the increase in specific beta-lactamase activity and the generation time, as well as the concentration of inducer in the medium. The specific beta-lactamase activity increased slowly within the first 0.5 generation and then more rapidly; it decreased regularly after about 2 generations of growth in the presence of inducer. This decrease could presumably be attributed to the continuous breakdown of inducer by beta-lactamases in the culture medium. In a chemostat culture with continuous supply of fresh inducer-containing medium, the specific beta-lactamase activity could be stabilized at a high level over several generations. Removal of the beta-lactam after a certain induction time showed that a short exposure of the bacteria to inducer caused induction kinetics comparable to those resulting from continuous exposure of the cells to inducer. The two beta-lactamases of P. maltophilia, L1 and L2, were induced simultaneously under various experimental conditions.
Rosta
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Pharmaceutical Division, CIBA-GEIGY Limited, Basel, Switzerland.
Mett
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H
D004790:Enzyme Induction; D015378:Imipenem / Q000494:pharmacology; D007700:Kinetics; D011549:Pseudomonas / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D013816:Thermodynamics; D001618:beta-Lactamases / Q000096:biosynthesis*
D015378:Imipenem; D001618:beta-Lactamases