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Impacts of sporulation temperature, exposure to compost matrix and temperature on survival of Bacillus cereus spores during livestock mortality composting

Stanford, K., Reuter, T., Gilroyed, B.H., McAllister, T.A.
Journal of applied microbiology 2015 v.118 no.4 pp. 989-997
Bacillus anthracis, Bacillus cereus, ambient temperature, bags, cattle, composting, composts, mortality, nylon, sawdust, spores, sporulation
AIMS: To investigate impact of sporulation and compost temperatures on feasibility of composting for disposal of carcasses contaminated with Bacillus anthracis. METHODS AND RESULTS: Two strains of B. cereus, 805 and 1391, were sporulated at either 20 or 37°C (Sporulation temperature, ST) and 7 Log₁₀ CFU g⁻¹spores added to autoclaved manure in nylon bags (pore size 50 μm) or in sealed vials. Vials and nylon bags were embedded into compost in either a sawdust or manure matrix each containing 16 bovine mortalities (average weight 617 ± 33 kg), retrieved from compost at intervals over 217 days and survival of B. cereus spores assessed. A ST of 20°C decreased spore survival by 1·4 log₁₀ CFU g⁻¹(P < 0·05) compared to a 37°C ST. Spore survival was strain dependent. Compost temperatures >55°C reduced spore survival (P < 0·05) and more frequently occurred in the sawdust matrix. CONCLUSIONS: Sporulation and compost temperatures were key factors influencing survival of B. cereus spores in mortality compost. SIGNIFICANCE AND IMPACT OF THE STUDY: Composting may be most appropriate for the disposal of carcasses infected with B. anthracis at ambient temperatures ≤20°C under thermophillic composting conditions (>55°C).