A method is provided. The method includes providing an article, the article including a nonwoven substrate having a copolymer grafted thereto, the copolymer including interpolymerized monomer units of a quaternary ammonium-containing ligand monomers; an amide monomer; an oxy monomer; and a coating on the nonwoven substrate, the coating including a plurality of test microorganisms, an enzyme or a second substrate; and contacting the article with a detection medium for a period of time.