Crown ethers: sensors for ions and molecular scaffolds for materials and biological models.

There are not many data available on antibiotics used solely in animals and almost exclusively for growth promotion. These products include bambermycin, avilamycin, efrotomycin, and the ionophore antibiotics (monensin, salinomycin, narasin, and lasalocid). Information is also scarce for bacitracin used only marginally in human and veterinary medicine and for streptogramin antibiotics. The mechanisms of action of and resistance mechanisms against these antibiotics are described. Special emphasis is given to the prevalence of resistance among gram-positive bacteria isolated from animals and humans. Since no susceptibility breakpoints are available for most of the antibiotics discussed, an alternative approach to the interpretation of MICs is presented. Also, some pharmacokinetic data and information on the influence of these products on the intestinal flora are presented.

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Antimicrobial Growth Promoters Used in Animal Feed: Effects of Less Well Known Antibiotics on Gram-Positive Bacteria

Mycotoxins represent one of the important classes of naturally occurring toxicants in food, posing considerable health risk. Biological decontamination of mycotoxins using microorganisms is one of the well-known strategies for the management of mycotoxins in foods and feeds. Among the different potential decontaminating microorganisms, Saccharomyces cerevisiae and lactic acid bacteria represent unique groups, which are widely used in food fermentation and preservation. This review discusses the available literature on the mycotoxin binding by S. cerevisiae and lactic acid bacteria and the scope of developments in the field.

Saccharomyces cerevisiae and lactic acid bacteria as potential mycotoxin decontaminating agents

Effects of active dry yeasts on the rumen microbial ecosystem : Past, present and future

Methods for preventing, decontaminating and minimizing the toxicity of mycotoxins in feeds

The cleavage of A23187 to give a synthon (4) and the semi-synthesis from (4) of 2 Des-N-methylamino A23187 isomers (7a,b) are described. The antibiotic activities of the acids analogous to A23187(1), (2), (7a), (7b) are compared.

Semi-synthesis of a23187 (calcimycin) analogs

Apparent molal volumes of the various forms of some ionophorous antibiotics in methanol have been obtained from density measurements. The discussion focuses on the shape and contraction of the various species according to their size and the number of hydroxylic groups which can participate through hydrogen bonding in the formation of the structure. More simple hydroxycarboxylic acids have also been studied to compare the effect of the chelation of these acids and the antibiotics on both the volume and dissociation constant.

Volumes of some ionophorous antibiotics (monensin, grisorixin and nigericin) according to their state in solution. Acid forms, anion and sodium and potassium salts

Processus de detoxification de la monensin, un anticoccidien. On determine la structure des trois produits obtenus apres bioconversion de l'antibiotique par Sebekia benihana NRRL IIIII. On evalue leur activite antibiotique in vitro et leurs proprietes ionophores

Bioconversion of monensin by a soil bacterium, Sebekia benihana

C25–C26 chemical derivatives of monensin (1) were prepared: 25-dehydroxymethyl, 25-oxo (2); 25,26-isopropyliden (3); 25-O-methyl (4); 26-O-acyl (5); 26-O-[N-chlorophenyl]carbamoyl (6); and 26-O-[N-chIorophenyl, N-methyl]carbamoyl (7). Measurements of Na+ and K+ extractions in a water/toluene–butanol (70:30) system by these analogs showed the key role of the C[26]H2–OH arm for the stability and selectivity of 1:1 complexes formed by monensin. The antibiotic activity and toxicity in mice were determined in relation to the Na+/K+ cationic affinity.

Georges Jeminet

Papers

Semi-synthesis of a23187 (calcimycin) analogs

Volumes of some ionophorous antibiotics (monensin, grisorixin and nigericin) according to their state in solution. Acid forms, anion and sodium and potassium salts

Bioconversion of monensin by a soil bacterium, Sebekia benihana

Analogs of Monensin with a Modified C25–C26 Moiety: Na+/K+ Selectivity and Biological Activity

Cationomycin and Monensin Partition between Serum Proteins and Erythrocyte Membrane: Consequences for Na+and K+Transport and Antimalarial Activities