Dry thermal resistance of Bacillus anthracis (Sterne) spores and spores of other Bacillus species: implications for biological agent destruction via waste incineration

Aims: To obtain needed data on the dry thermal resistance of Bacillus anthracis spores and other Bacillus species for waste incinerator applications.

Methods and results: Tests were conducted in a pilot-scale incinerator utilizing biological indicators comprised of spores of Geobacillus stearothermophilus, Bacillus atrophaeus and B. anthracis (Sterne) and embedded in building material bundles. Tests were also conducted in a dry heat oven to determine the destruction kinetics for the same species. In the pilot-scale incinerator tests, B. atrophaeus and G. stearothermophilus demonstrated similar thermal sensitivity, but B. anthracis (Sterne) was less thermally resistant than G. stearothermophilus. For the dry heat oven tests conducted at 175°C, the D-values were 0·4, 0·2 and 0·3 min for B. atrophaeus, B. anthracis (Sterne) and G. stearothermophilus, respectively.

Conclusions: Bacillus anthracis (Sterne) possesses similar or less dry heat resistance compared to B. atrophaeus and G. stearothermophilus.

Significance and impact of the study: Previous studies have demonstrated conditions under which bacterial spores may survive in an incinerator environment. The data from this study may assist in the selection of surrogates or indicator micro-organisms to ensure B. anthracis spores embedded in building materials are completely inactivated in an incinerator.