Recovery of spores of Clostridium difficile altered by heat or alkali

The effect of heating or alkali-treatment on spore recovery in ordinary growth medium was examined for four strains of Clostridium difficile. Heating spores at 80 degrees C for 10 min produced 95.50-99.95% decreases in the recovery rates. Treatment with 0.1 N NaOH for 15 min produced 99.47 and 99.83% decreases in spore recovery rates for two of the four strains. The influence of either addition of lysozyme after treatment with sodium thioglycollate (thioglycollate-lysozyme method) or addition of sodium taurocholate (taurocholate method) on recovery of heat- or alkali-treated C. difficile spores was also examined. Viable spores of all strains altered by heating at 90 degrees C or 100 degrees C for 10 min could not be recovered at all by the taurocholate method. Nor did this method allow recovery of alkali-altered spores treated with greater than 0.2 N NaOH for 15 min. On the other hand, 10-47% of altered spores heated at 90 degrees C for 10 min were recovered by the thioglycollate-lysozyme method, and alkali-altered spores treated with 0.1-0.3 N NaOH for 15 min were as completely recovered by this method as untreated spores. These results indicate that the thioglycollate-lysozyme method is more effective than the taurocholate method for recovery of the heat- or alkali-altered C. difficile spores.