Preliminary experiments indicated that C. perfringens spore germination in BHI broth exhibited a similar extent of germination in the presence of 50 or 100 mM AK, thus 50 mM AK was used in this study. No difference was observed in the extent of spore germination with filter-sterilized and autoclaved (121 C, 20 min) germinant solutions, thus germinant solutions were autoclaved.