Phenelfamycin A

Six kirromycin analogs (elfamycins) were compared on the basis of their inhibition of Escherichia coli poly(U)-directed poly(Phe) synthesis and stimulation of elongation factor Tu (EF-Tu)-associated GTPase activity. The elfamycins tested were kirromycin, aurodox, efrotomycin, phenelfamycin A, unphenelfamycin, and L-681,217. The last three lack the pyridone ring present in the other elfamycins. All the elfamycins inhibited poly(U)-dependent poly(Phe) synthesis and stimulated EF-Tu-associated GTPase activity, suggesting that the pyridone ring is not essential for activity. The six elfamycins were also examined in a poly(U)-directed, poly(Phe)-synthesizing system derived from Staphylococcus aureus and had 50% inhibitory concentrations of greater than or equal to 1 mM. When S. aureus ribosomes and E. coli elongation factors were combined in a hybrid poly(Phe)-synthesizing system, aurodox produced essentially complete inhibition of poly(Phe) synthesis with a 50% inhibitory concentration of 0.13 microM. This suggests that the observed high MICs of kirromycin and its congeners in S. aureus reflect a kirromycin-resistant EF-Tu rather than permeability constraints.

Phenelfamycins A, B, C, E, F and unphenelfamycin make up a recently isolated group of elfamycin-type antibiotics. All of the phenelfamycins were active against Gram-positive anaerobes, including Clostridium difficile. Phenelfamycin A was also active in vitro against Neisseria gonorrhoeae and Streptococci. Phenelfamycin A was found to be effective in prolonging the survival of hamsters in an animal model of C. difficile enterocolitis. After oral administration of phenelfamycin A to hamsters, antibiotic was detected in the caecal contents but not in the blood.