GRAMICIDIN IS A BACTERICIDAL FOR A VARIETY OF GRAM-POSITIVE ORGANISMS. IT IS ACTIVE AGAINST THESE MICROORGANISMS :- STAPHYLOCOCCUS AUREUS, STREPTOCOCCI, INCLUDING STREPTOCOCCUS PNEUMONIAE. IT INCREASES THE PERMEABILITY OF THE BACTERIAL CELL MEMBRANE TO INORGANIC CATIONS BY FORMING A NETWORK OF CHANNELS THROUGH THE NORMAL LIPID BILAYER OF THE MEMBRANE.