A self-contained biological sterilization indicator comprises: a housing; bacterial spores comprising, and/or capable of producing, an enzyme capable of catalyzing cleavage of an enzyme substrate; and a frangible container containing a composition, wherein the composition comprises the enzyme substrate, wherein if the frangible container is broken the composition will contact the bacterial spores to form a mixture having an initial pH in the range from 6.0 to 9.0. The enzyme substrate comprises a fluorinated 4′-alkylumbelliferyl α-D-glucopyranoside represented by the structural formula (I) wherein one of R1 and R2 is F and the other is H, and R3 is an alkyl group having from 1 to 12 carbon atoms. A biological sterilization indicator comprising a kit containing isolated components comprising (i) bacterial spores comprising, and/or capable of producing, an enzyme capable of catalyzing cleavage of the enzyme substrate and a method of assessing efficacy of a sterilization process are also disclosed.