The Resistances of Spores of the Genus Bacillus to Phenol, Heat and Radiation

S ummary . The resistance of the spores of 6 species of Bacillus to 5% (w/v) of phenol at 37°, heat and gamma radiation has been determined. Two, and with heat treatment three, different shapes of log survivor time curves were observed with each lethal agent. In relation to the conditions employed in accepted sterilization procedures, all of the strains were highly resistant to phenol. Bacillus stearothermophilus, B. licheniformis and B. subtilis were resistant to gamma radiation, all three having a D value of 0.22 Mrad. Only B. stearothermophilus was heat resistant having a D value of 22.6 min at 115°. When the relative order of resistance to each agent was considered, with the exception of B. stearothermophilus , the spores showed little evidence of any relationship between their resistances to phenol, heat and gamma radiation.