Search

This paper is dealing with the enzymatic problem raised by two strains of Ps. aeruginosa resistant to classical beta lactam antibiotics including carbenicillin. These two strains hydrolyse all these antibiotics. In both cases, we have shown the simultaneous biosynthesis of two enzymes: an inducible and chromosome cephalosporinase frequently found in this germ, and a constitutive beta lactamase, with a penicillinase activity which has been identified with the extrachromosomic beta lactamase R-TEM. These two enzymes have been separated by affinity chromatography, characterized by their kinetic constants given by computerized microacidimetry, and their isoelectric points which are respectively 9.2 for the cephalosporinase and 5.40 for the penicillinase R-TEM. Isoelectric focussing also shows the separation of these two enzymes.

It has been shown that two Proteus morganii strains produce an inducible cephalosporinase. No significative difference was shown between them: they present the same isoelectric poit: 8,3 and very similar kinetic constants. The parameter tau, proportional to the half life of antibiotic at low concentration, in presence of beta lactamase, shows that cefamandole is the most stable cephalosporin studied.

Pseudomonas aeruginosa strain RL 39 produces an inducible cephalosporinase possessing an isoelectric point of 8,66. The kinetic constants have been measured by computerized microacidimetry. The results allow to differenciate this enzyme from the one produced by Ps. aeruginosa GN 918 (Yaginuma et al. (1973) Jap. J. Microbiol., 17, 141-149) showing a similar isoelectric point.