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The in vitro and in vivo antibacterial activities of carumonam (AMA-1080), a synthetic sulfazecin derivative, were compared with those of aztreonam, cefoperazone, ceftazidime, and cefsulodin.

Cefmenoxime, a new cephalosporin antibiotic, has been shown to be stable to a Staphylococcus aureus penicillinase and R plasmid-mediated type I and type IV penicillinases. It was also resistant to hydrolysis by most cephalosporinases, but was susceptible to hydrolysis by a Proteus vulgaris beta-lactamase. Cefmenoxime was active against cephaloridine-resistant species, except Pseudomonas aeruginosa, which was moderately resistant to cefmenoxime. Cefmenoxime was an inducer of P. vulgaris beta-lactamase biosynthesis, but 1 microgram or more of the drug per ml, which inhibits most of the clinical isolates of P. vulgaris, was required for the production of detectable amounts of the enzyme. Cefmenoxime was a strong competitive inhibitor of beta-lactamases of Enterobacter cloacae, Citrobacter freundii, P. aeruginosa, and Serratia marcescens, but it did not inhibit penicillinases in spite of its resistance to hydrolysis.

A number of Streptom yces strains degraded the N-glycosidic linkage of pyrimidine nucleotides. The products and some conditions of 5'-UMP degradation were studied using cell-free extracts of Streptomyces virginiae IFO 3729. Formation of uracil was recognized by paper electrophoresis and by the shift of ultraviolet absorption at an alkaline pH. Pentose phosphate was purified by ion-exchange chromatography and prepared as Ba salt. It was identified with R5P by paper chromatography, paper electrophoresis and by chemical analyses. Optimum pH and temperature for R5P formation were 5.5 and 55°, respectively. 5'-UMP was quantitatively converted to uracil and R5P under this condition. At near neutral pH and at lower temperatures, the rate of R5P formation was far lower than that of uracil, caused by coexisting R5P-metabolizing activity. When the mixture of purine and pyrimidine nucleotides was subjected to the enzyme action, pyrimidine nucleotides were selectively degraded. The hydrolysis of nucleoside N-glycosidic linkage is well known, but reports on the hydrolysis at the nucleotide level are scarce. HURWITZ et al. (1) found in Azotobacter vinelandii AMP-ribosidase which hydrolyzes 5'-AMP to adenine and ribose-5-phosphate (R5P). KUNINAKA (2, 3) reported on IMPribosidase of Aspergillus oryzae, which hydrolyzes 5'-IMP and 5'-GMP to their bases and R5P. These reports are mainly concerned with the cleavage of purine nucleotides. During the course of our investigation on the metabolism of pyrimidine compounds by microorganisms, the ability of Streptonyees to hydrolyze the N-glycosidic linkage in pyrimidine 5'-nucleotides was found. This paper deals with the distribution of such an enzyme, the degradation products and with some conditions for the degradation of the nucleotides.

Various P-lactam antibiotics, including monocyclic P-lactams, induced the P-lactamase of Proteus vulgaris; when clinical isolates were induced by benzylpenicillin, each strain produced a single 0-lactamase but the activity per milligram dry weight differed from strain to strain. The Plactamases of the P. vulgaris strains were heterogeneous with respect to their isoelectric points, but had almost the same specific activities, substrate specificities and Michaelis constants. The kinetics of P-lactamase formation were investigated in three strains, each with a different /Ilactamase activity. Differential rates of enzyme synthesis and peak activity depended on the concentration of inducer. The plots of the reciprocals of the differential rates versus the reciprocals of the inducer concentrations were linear, and the maximum rate of enzyme synthesis and the concentration of the inducer giving half-maximum induction were determined from this double reciprocal plot. The maximum rates of enzyme synthesis were different in the three strains. The kinetic analysis of /I-lactamase formation revealed that the P-lactamase activities in a single bacterial species were determined by differences in the rate of enzyme synthesis and not by differences in the properties of the enzyme.