Abstract
Representative polyethers of each group in Westley's classification and related ionophore antibiotics were examined for in vitro activity against 25 anaerobic strains. Lasalocid (X-537A) and nigericin were found to have activity comparable in potency to some leading antianaerobe antibiotics, newer cephalosporins and nitroimidazoles, with a different spectrum as revealed by a spectral comparison. A strict relationship between their antianaerobe activity and either their structural features or cation transporting properties was not apparent.