Biological indicators for low temperature steam formaldehyde sterilization: effect of defined media on sporulation, germination index and moist heat resistance at 110 degrees C of Bacillus strains.

Choice of a biological indicator depends upon selecting a strain with the optimum balance of desirable properties. Screening 20 strains of Bacillus spp. for sporulation on three defined media has shown the wide variation that occurs in requirements for sporulation and properties of the resultant spores. Comparison of germination index and moist heat resistance of resultant spores suggest that a combination of high germination index, high heat resistance and linear inactivation may not be possible.