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At least 235 records · Page 13Linked to original sources
PubMed1977

Macrolide antibiotics M-4365 produced by Micromonospora. II. Chemical structures.

By physiochemical analyses and chemical procedures, the structures of a series of basic 16-membered macrolide antibiotics, M-4365, A1, A2, A3, G1, G2 and G3 were elucidated, and it was found that M-4365 A1, G1 and G2 were novel, while M-4365 A2, A3 and G3 were identical with rosamicin, juvenimicins A4 and B1, respectively.

Aminoglycosides↗
PubMed1980

Izumenolide-a novel beta-lactamase inhibitor produced by Micromonospora. II. Biological properties.

Izumenolide is a potent inhibitor of beta-lactamases, especially from Gram-negative bacteria. The I50 value of 0.01 microgram/ml for TEM-2 beta-lactamase, after 10 min preincubation, corresponds to a ratio of 7.6 moles inhibitor per mole of enzyme. The initial inhibitory reaction with TEM-2 beta-lactamase exhibits mixed reaction kinetics, suggesting a possible overlapping binding site with the active center. Tem-2 beta-lactamase is irreversible inactivated by izumenolide in a biphasic reaction. Carbenicillin offers partial protection against inactivation. Izumenolide exhibits limited antibiotic activity against some Gram-negative bacteria. Against beta-lactamase producing bacteria izumenolide provides protection to ampicillin and cephaloridine but the protection is limited due to permeability problems associated with izumenolide entry into the cells.

Animals↗
PubMed1981

Macrolide antibiotics M-4365 produced by Micromonospora. IV. Antimycoplasmal activity of antibiotic M-4365 G2 (de-epoxy rosamicin).

In vitro activities of M-4365 G2, a new basic 16-membered macrolide antibiotic, against a total 19 strains including human, bovine, porcine, rodent, avian and saprophytic mycoplasmas were compared with those of three other macrolide antibiotics, josamycin, erythromycin and tylosin. M-4365 G2 exhibited stronger activities than the other macrolide antibiotics against 11 strains of mycoplasma tested. Especially, its higher activities against M. pneumoniae Mac and FU, U. urealyticum T-960, M. mycoides PG-1 and M. gallisepticum Kp-13, PG-31 and 9-49A were to be noticed (final minimum inhibitory concentrations: 0.0001 approximately 0.049 microgram/ml). Higher antimycoplasmal activity of M-4365 G2 than that of tylosin was also proved in experimental treatment of chickens intranasally inoculated with M. gallisepticum Kp-13 by feeding a diet containing the drug. M. gallisepticum Kp-13 was not isolated from the infected chickens fed a diet containing 0.0063% or more of M-4365 G2.

Anti-Bacterial Agents↗
PubMed1983

Studies on a new antibiotic M-92 produced by Micromonospora. IV. Bactericidal action of the component VA-2.

The action of VA-2, the most active component of antibiotic M-92, against S. aureus is bactericidal but not bacteriolytic. The bactericidal action is markedly affected by incubation temperature, whether bacterial cells are prolific or resting. The bactericidal kinetics of VA-2 is biphasic, since addition of VA-2 caused rapid and straight decrease in viability curve and reached a plateau after several minutes. The bactericidal activity of VA-2 is blocked by 2,4-dinitrophenol. Alike to many membrane-active bacteriocins, VA-2 seems to exert its action through two stages.

2,4-Dinitrophenol↗
PubMed1983

Studies on a new antibiotic M-92 produced by micromonospora. V. Mechanism of action of the component VA-2.

Effects of VA-2, a component of quinoid antibiotic M-92, on the incorporation of radioisotope-labeled compounds into the cells of Staphylococcus aureus were studied. Deoxyribonucleic acid (DNA) synthesis was immediately inhibited by the addition of VA-2. Significant inhibitions of ribonucleic acid and protein syntheses and minor reduction of peptidoglycan synthesis were observed after a short delay. VA-2 immediately induced the degradation of DNA prelabelled with [14C]thymidine in the cells of S. aureus. In the examinations using E. coli enzyme and calf thymus DNA as a template, VA-2 prevented DNA-dependent DNA polymerase reaction. The inhibition of DNA polymerase I reaction was fairly reversed by increasing the concentration of template DNA, but slightly by that of the enzyme. Agarose gel electrophoresis showed that VA-2 elicited an extensive cleavage of PM2 cccDNA. VA-2 caused a primary conversion of the cccDNA to ocDNA at a low concentration (0.2 micrograms/ml), while at high concentrations (2.0 and 20 micrograms/ml) it cleaved the cccDNA to ocDNA and linear DNA progressively. These cleavages were observed even at 0 degrees C as well as at 37 degrees C, and were enhanced with the addition of a reducing agent such as 2-mercaptoethanol or sodium borohydride.

Anti-Bacterial Agents↗