A new semisynthetic cephalosporin antibiotic designated 7-beta-(1-benzylpyridinium-4-yl)-amino-3-[( (1-methyl-1H-tetrazol-5-yl) thio]methyl)ceph-3-em-4-carboxylate (L-640,876) was compared for antibacterial activity in vitro with mecillinam, cefoxitin and cefotaxime. The antibacterial spectrum of L-640,876 and the effect of culture medium composition and inoculum size on activity are most similar to those of mecillinam. In some cases the inoculum effect on MICs correlated with instability of the compound to certain beta-lactamases and in others to the presence of ionized compounds such as sodium chloride in the medium. On balance, L-640,876 was superior to mecillinam in potency and breadth of spectrum.
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Two newly described quaternary heterocyclylamino beta-lactams, L-642,946 and L-652,813, were shown to exhibit potent activity against a broad spectrum of aerobic and anaerobic bacteria in vitro. The activity of these agents in vitro translated well to chemotherapeutic activity in experimental bacteremias in mice. Substitution of the thiadiazine moiety of L-642,946 with a triazine moiety effected a marked change in the pharmacokinetics of the new derivative, L-652,813.
View Article and Find Full Text PDFA new semisynthetic cephalosporin antibiotic designated L-640,876, 7-beta-(1-benzylpyridinium-4-yl)amino-3-[( (1-methyl-1H-tetrazol-5-yl)thio] methyl)ceph-3-em-4-carboxylate, was highly active in vitro against 110 enteropathogenic strains of Escherichia coli and Salmonella species of animal origin. The MIC90 was 0.125 microgram/ml for the E.
View Article and Find Full Text PDFL-640,876, 7-beta(1-benzylpyridinium-4-yl)amino-3-[( (1-methyl-1 H-tetrazol-5-yl)thio]methyl)-ceph-3-em-4-carboxylate, is a potent representative of a new family of beta-lactam antibiotics which are similar in some respects to mecillinam. When L-640,876 and mecillinam were compared for effects on growth and morphology of Escherichia coli, it was observed that both drugs caused the formation of lemon-shaped cells during the first 30 minutes of exposure and during this period the culture turbidity increased without an appreciable change in culture viability. Unlike mecillinam, after 60 minutes of exposure to L-640,876 the majority of the lemon-shaped cells transformed into spindle-shaped cells and in the continuing presence of the drug formed osmotically fragile spheroplasts.
View Article and Find Full Text PDFThe novel beta-lactam, L-640,876, exhibited excellent therapeutic activity when administered parenterally but not orally to mice infected with a variety of pathogenic bacteria. In this respect, the compound was as potent as cefotaxime against representative Gram-positive and Gram-negative organisms, in most cases, equal to or more potent than cefoxitin, and more effective than mecillinam. When administered subcutaneously to normal mice at dose levels ranging from 10 to 50 mg/kg, L-640,876 provided an adequate dose response, recovery of ca.
View Article and Find Full Text PDFA new semisynthetic cephalosporin antibiotic designated 7-beta-(1-benzylpyridinium-4-yl)-amino-3-[( (1-methyl-1H-tetrazol-5-yl) thio]methyl)ceph-3-em-4-carboxylate (L-640,876) was compared for antibacterial activity in vitro with mecillinam, cefoxitin and cefotaxime. The antibacterial spectrum of L-640,876 and the effect of culture medium composition and inoculum size on activity are most similar to those of mecillinam. In some cases the inoculum effect on MICs correlated with instability of the compound to certain beta-lactamases and in others to the presence of ionized compounds such as sodium chloride in the medium.
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