Influence of membrane composition of various parasites on the inhibitory activity of a series of bipyridyl analogues.

In a previous report the dependence of the antimycoplasmal activity of bipyridyl analogues on the presence of Cu+ ions has been shown. The inhibitory activity of these compounds has now been studied against Escherichia coli mycobacteria and Candida albicans in the absence and presence of Cu2+ ions using growth kinetic techniques. It was found that the inhibitory activity against E. coli increases in the presence of Cu2+ ions. In contrast, no additional effect of Cu2+ ions is observed for the inhibitory activity against mycobacteria. Some of the derivatives show very promising activity even against Mycobacterium avium strains. More complicated is the effect of Cu2+ ions on the inhibitory activity of the derivatives against C. albicans. For isoquinolones the observed delay in onset of inhibitors is reduced and no influence on the inhibitory activity is observed. The addition of Cu2+ ions to the phenanthrolines leads in contrast to a decrease in antifungal activity. The possible influence of membrane properties of the studied microorganism on the effect of Cu2+ ions is discussed.