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

Abstract

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.

Bacillus thuringiensisHD-1 Cry−: development of a safe, non-insecticidal simulant forBacillus anthracis

“…; Greenberg et al ., ; Wood et al . ). The latter point is important because, with increasing molecular tools available, it is desirable to find direct orthologues of genes, found to be of interest in the genome of the surrogate, in that of B. anthracis and vice versa .…”

Inactivation of Geobacillus stearothermophilus spores by alkaline hydrolysis applied to medical waste treatment

“…Indeed, the low water content in the core and the intrinsic thermostability of proteins confers to spores of thermophilic species a higher resistant to wet heat than to those of mesophiles (Guizelini et al, 2012). Therefore, the spores of this organism are often used as a biological indicator to assess the effectiveness of sterilization methods (Lo 'pez et al, 1997;Watanabe et al, 2003;Wood et al, 2010).…”

Thermal inactivation of Bacillus anthracis surrogate spores in a bench-scale enclosed landfill gas flare

“…Bacillus atrophaeus (ATCC 9372; Apex Laboratories, Apex, NC) and Geobacillus stearothermophilus (ATCC 7953; Apex Laboratories) spores were chosen as surrogates for B. anthracis in this study. B. atrophaeus is commonly seen in the literature as a surrogate for B. anthracis, and because both of the selected surrogates are similarly resistant to dry heat as B. anthracis (Wood et al, 2010) and have been used as biological indicators in sterilization processes, they are excellent indicators to demonstrate the fate of B. anthracis in a landfill flare. Previous work (Wood et al, 2010) determined the dry heat F-value, the time (in minutes) that causes the complete destruction of microorganisms (U.S. Department of Agriculture, 2005), at 200 C for G. stearothermophilus and B. atrophaeus to be 1.3 and 1.1 min, respectively; these times are similar to the F-value of 1.2 min for B. anthracis at the same temperature.…”