Abstract Materials fabricated from fibrous proteins or other nitrogenous, amphoteric, film-forming, organic materials such as polymers, such as fibers, threads, films, yarns, fabrics and finished textile products, are provided with long-lasting germicidal properties by chemically combining germicidal ions with the nitrogenous, amphoteric, substrate. The germicidal ions are substantially incapable of being solvent extracted from the substrate which indicates that the ions have been chemically bonded thereto. For example, sutures, such as silk sutures, can be rendered germicidal for long periods of time by contacting a silk suture with an aqueous solution of a cationic or anionic germicidal surface active agent such as a germicidal quaternary ammonium salt or a germicidal organic sulfonate, to chemically bond the germicidal cation or anion of the salt to the proteinaceous substrate. The cationic or anionic germicidal agents can both be sequentially applied to the section containing both cationic and anionic germicidal ions bonded thereto.