Effect of heat-shock treatment on the survival of Escherichia coli O157:H7 and Salmonella enterica Typhimurium in dairy manure co-composted with vegetable wastes under field conditions

This study investigated the survival of heat-shocked (HS) and non-heat-shocked (NHS) Escherichia coli O157:H7 and Salmonella enterica Typhimurium when co-composting dairy manure and vegetable wastes in a field setting. In the summer, HS E. coli O157:H7 and Salmonella survived for 7 and 2 days longer at the surface and bottom locations of the compost heaps, respectively, than NHS cultures. Both HS and NHS E. coli O157:H7 and Salmonella were detectable in all compost samples for more than 60 days in the winter. The results indicate that composting dairy manure with vegetable wastes under sub-optimal conditions may allow extended survival of pathogens in the heap at low ambient temperature. Analysis of covariance revealed that the heat-shock treatment may have induced cross-resistance to desiccation, allowing extended survival of HS E. coli O157:H7 and Salmonella at the surface of the compost heaps during the summer.