Recovery of spores of Clostridium difficile altered by heat or alkali

Abstract

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°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°C or 100°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 > 0·2 n NaOH for 15 min. On the other hand, 10–47% of altered spores heated at 90°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.