Abstract

The elfamycins are so named because they exhibit antimicrobial activity through the inhibition of protein biosynthesis via binding to the elongation factor Tu. Known elfamycins include aurodox, C₄₄H₆₂N₂O₁₂; kirromycin, C₄₃H₆₀N₂O₁₂; azdimycin, efrotomycin, C₅₉H₈₈N₂O₂₀; dihydromocimycin, C₄₃H₆₂N₂O₁₂; heneicomycin, C₄₄H₆₂N₂O₁₁; kirrothricin, C₄₄H₆₄N₂O₁₀; factumycin, C₄₄H₆₂N₂O₁₀; MSD A63A, L681,217, C₃₆H₅₃N₁O₁₀; SB22484, factor 3, C₄₁H₅₆N₂O₁₁; SB22484, factor 4, C₄₂H₅₈N₂O₁₁; phenelfamycin A, C₅₁H₇₁N₁O₁₅; phenelfamycin B, C₆₁H₇₁N₁O₁₅; phenelfamycin C, C₅₈H₈₃N₁O₁₈; phenelfamycin D, C₅₈H₈₃N₁O₁₈; phenelfamycin E, C₆₅H₉₅N₁O₂₁; phenelfamycin F, C₆₅H₉₅N₁O₂₁; unphenelfamycin, C₄₃H₆₅N₁O₁₄; LL-E19020, C₆₅H₉₅N₁O₂₁; LL-E19020, C₆₅H₉₅N₁O₂₁; UK-69,753, C₅₈H₈₆N₂O₁₈; and N-demethylefrotomycin, C₅₈H₈₆N₂O₂₀. These antibiotics are distinguished by low mammalian toxicity, narrow-range antimicrobial activity, and positive effects on feed utilization and growth promotion in farm animals. Elfamycins are natural products. Aurodox and efrotomycin have been synthesized chemically. Elfamycins are slightly acidic and soluble in most polar organic solvents, and the alkali and ammonium salts are water-soluble. Elfamycins block bacterial protein biosynthesis at the level of elongation factor Tu (EF-Tu). Elfamycins have similar in vitro antimicrobial spectra and the activity against Moraxella, Pasteurella, Yersinia, Haemophilus, Streptococcus, Corynebacterium, and Neisseria appears to be common. Elfamycins, in general, enhance the growth of farm animals. Efrotomycin is being developed as a growth-promoting agent for swine. The potential usefulness of elfamycins as growth promotors and feed-conversion enhancers is now generally recognized. Low original fermentation yields and difficulties in yield improvements discouraged early attempts to develop aurodox and mocimycin (kirromycin) commercially. A development program for efrotomycin, however, is ongoing. Some of the newer elfamycins, such as the LL-E19020 pair, are considerably more active growth promotors than aurodox or mocimycin, pointing toward a second generation of elfamycins.