Escherichia coli resistance to neurosporin can be sensitive to resistant strains by eliminating their outer membrane resistance. The polycationic antibiotic, Nourseothricin, represents a mixture of several Streptothricins, mainly D and F. Obviously, although very slowly, it can pass the outer membrane via the porin pores. It has been shown earlier that Nourseothricin is able to generate some kind of channels into the outer membrane through which it can pass the cell wall. On the other hand, there are indications that resistant strains containing a Nourseothricin-inactivating acetyl transferase possess an additional protecting system, namely a reduced penetrability of the outer membrane.