The invention relates to use of a composition comprising a cationic surfactant, which comprises a primary or secondary ammonium head group and a linear unsubstituted C12-alkyl tail, for inducing germination of bacterial endospores in pulp suspension for making of paper, board or the like. The invention relates also to a method for quantitatively reducing bacterial endospores in pulp suspension for making of paper, board or the like. The method comprises obtaining of aqueous pulp suspension, and administering the said composition to the pulp suspension. The cationic surfactant is allowed to interact with bacterial endospores in the pulp suspension. Germination of endospores and destroying microorganisms is thus induced.