The efficiency of four culture media for recovery of heat-activated and heated Clostridium sporogenes spores was studied. Yeast extract agar gave the highest spore recovery. The effect of the method of preparing the yeast extract agar on the recovery of heated spores was also evaluated. The results indicate that (a) a significantly lower spore recovery was obtained when the dextrose was omitted completely or when added to the medium before autoclaving, and (b) no significant difference in spore recovery was found between yeast extract agar freshly made or prepared and stored at 4 C up to 11 days before use.
1Paper No. 10,775, Scientific Journal Series, Minnesota Agricultural Experiment Station, St. Paul, MN 55108.