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

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(-1) spores 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).