Laboratory heating studies with Salmonella spp. and Escherichia coli in organic matter, with a view to decontamination of poultry houses

AIMS: To determine a temperature-humidity-time treatment that eliminates Salmonella and Escherichia coli in substrates representing organic matter in poorly cleaned poultry houses, i.e. worst case scenario laboratory tests. METHODS AND RESULTS: Organic matter (poultry faeces and feed) in a 2.5-cm layer was inoculated with 2 x 10(5)-3 x 10(6) Salmonella g(-1), left undried or dried at ca. 30% relative humidity (RH) during a 10-day period, and temperature increased at 1 degrees C h(-)1 to the final heating temperature of 50, 55, 60, 65 or 70 degrees C and held at 16-30 or 100% RH. All samples were tested for Salmonella according to predetermined sampling time schedules and faecal samples were also tested for naturally occurring E. coli. Overall, humidity was an important factor in the elimination of Salmonella and E. coli. Results for recovery of Salmonella and E. coli were highly associated. CONCLUSIONS: The application of >/=60 degrees C and 100% RH during a 24-h period eliminated Salmonella and E. coli in all samples. Escherichia coli could be used as an indicator bacterium for the elimination of Salmonella. SIGNIFICANCE AND IMPACT OF THE STUDY: The results from worst case scenario laboratory tests could be applied in steam heating of persistently Salmonella-infected poultry houses. The use of E. coli as an indicator bacterium for the validation of Salmonella results should be considered.