Conditions suitable for the recovery of biocide-treated spores of Bacillus subtilis.

ABSTRACT

Various factors were studied in order to determine the optimum conditions for the recovery of Bacillus subtilis spores treated with two iodine preparations, two chlorine-releasing agents or glutaraldehyde. The composition of the recovery medium was not usually important except that counts on brain heart infusion agar were significantly lower than on other media for iodine-treated spores. The addition to recovery media of soluble starch, charcoal, D-glucose or yeast extract usually had no discernible beneficial effect on colony counts. Maximum counts of survivors were obtained after an incubation period of 3 days and an optimum incubation temperature of 30 or 37 degrees C. Germination and outgrowth of biocide-exposed spores were more sensitive to changes in incubation temperature than were control spores.