title: Heat and desiccation are the predominant factors affecting inactivation of Bacillus licheniformis and Bacillus thuringiensis spores during simulated composting.
abstract: OBJECTIVE
  The suitability of composting for disposal of livestock mortalities due to Bacillus anthracis was assessed by measuring viability of surrogate spores from two strains each of Bacillus licheniformis and Bacillus thuringiensis after a heating cycle modelled on a cattle composting study.
  
  
  RESULTS
  Sporulation was attempted from 10 to 37°C, but poor yields at lower temperatures resulted in 25, 30 and 37°C being selected to generate sufficient spores (8 log10  CFU ml(-1) ) for experiments. Spores were inoculated into 3 g autoclaved dried-ground compost rehydrated with 6 ml water or silica beads in a factorial design for each strain, sporulation temperature, matrix and sampling day (0, 25, 50, 100, 150). Maximum incubation temperature was 62°C, but spores were maintained at ≥55°C for 78 of 150 days. Although significant differences existed among Bacillus strains and sporulation temperatures, numbers of viable spores after 150 days averaged 1·3 log10  CFU g(-1) , a 5·2 log10 reduction from day 0.
  
  
  CONCLUSIONS
  Spore inactivation was likely due to heat and desiccation as matrices were autoclaved prior to incubation, negating impacts of microflora.
  
  
  CONCLUSIONS
  Results support composting for disposal of anthrax mortalities, provided long-term thermophillic heating is achieved. Due to limited sporulation at 10°C, livestock mortalities from anthrax at this or lower ambient temperatures would likely be of lower risk for disease transmission.
authors.affiliation: Alberta Agriculture and Forestry, Lethbridge, AB, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Stanford
authors.affiliation: University of Lethbridge, Lethbridge, AB, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Harvey
authors.affiliation: Agriculture and Agri-Food Canada, Lethbridge, AB, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Barbieri
authors.affiliation: Agriculture and Agri-Food Canada, Lethbridge, AB, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Xu
authors.affiliation: Alberta Agriculture and Forestry, Lethbridge, AB, Canada.
authors.forename: T
authors.initials: T
authors.lastname: Reuter
authors.affiliation: Canadian Food Inspection Agency, Lethbridge, AB, Canada.
authors.forename: K K
authors.initials: KK
authors.lastname: Amoako
authors.affiliation: University of Lethbridge, Lethbridge, AB, Canada.
authors.forename: L B
authors.initials: LB
authors.lastname: Selinger
authors.affiliation: Agriculture and Agri-Food Canada, Lethbridge, AB, Canada.
authors.forename: T A
authors.initials: TA
authors.lastname: McAllister
mesh_terms: D000818:Animals; D001407:Bacillus / Q000737:chemistry / Q000254:growth & development*; D001413:Bacillus thuringiensis / Q000737:chemistry / Q000254:growth & development*; D002417:Cattle; D003890:Desiccation; D006358:Hot Temperature; D050296:Microbial Viability; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013171:Spores, Bacterial / Q000737:chemistry / Q000254:growth & development; D013242:Sterilization; D013696:Temperature
chemical_list: D012987:Soil
keywords: Bacillus anthracis; Bacillus licheniformis; Bacillus thuringiensis; compost; spore inactivation