ORIGINAL ARTICLE Selection of indigenous indicator micro-organisms for validating desiccation-adapted Salmonella reduction in physically heat-treated poultry litter Z. Chen 1 and X. Jiang 2 1 Department of Biological Sciences, Clemson University, Clemson, SC, USA 2 Department of Food, Nutrition, and Packaging Sciences, Clemson University, Clemson, SC, USA Keywords desiccation, enterococci, indicator, indigenous microflora, Poultry litter, Salmonella Senftenberg 775/W, total aerobic bacteria. Correspondence Xiuping Jiang, Department of Food, Nutrition, and Packaging Sciences, Clemson University, Clemson, SC 29634, USA. E-mail: xiuping@clemson.edu 2016/2233: received 14 October 2016, revised 20 February 2017 and accepted 24 March 2017 doi:10.1111/jam.13464 Abstract Aims: The thermal resistance of desiccation-adapted Salmonella Senftenberg 775/W was compared with those of indigenous enterococci and total aerobic bacteria in poultry litter. Methods and Results: Aged broiler litter and composted turkey litter with 20, 30, 40 and 50% moisture contents were inoculated with desiccation-adapted Salm. Senftenberg 775/W, and then heat-treated at 75 and 85°C. Compared to total aerobic bacteria, there were better correlations between mean log reductions of desiccation-adapted Salm. Senftenberg 775/W and indigenous enterococci in broiler litter samples with 20, 30, 40 and 50% moisture contents at 75°C (R 2 > 0Á91), and 20, 30 and 40% moisture contents at 85°C (R 2 > 0Á87). The mean log reductions of Salm. Senftenberg 775/W were better correlated with those of indigenous enterococci in turkey litter samples with 20, 30, 40 and 50% moisture contents at 75°C(R 2 > 0Á88), and 20 and 30% moisture contents at 85°C(R 2 = 0Á83) than those of total aerobic bacteria, which had a better correlation in turkey litter sample with 40% (R 2 = 0Á98) moisture content at 85°C. Conclusion: Indigenous enterococci may be used to validate the thermal processing of poultry litter, as it predicts the survival behaviour of Salmonella under some treatment conditions. Significance and the Impact of the Study: This study provides some scientific data for poultry litter processors when validating the effectiveness of thermal processing. Introduction According to the U.S. Department of Agriculture (USDA) National Agricultural Statistics Service’s 2015 Census of Agriculture, the U.S. produced more than 8Á5 billion broilers and 2Á3 billion turkeys in 2015 (USDA 2015). Since broilers and turkeys produce about 1Á7 and 18 pounds of litter per bird respectively (West Virginia Regional Planning and Development Councils 2012), it is estimated that the broilers and turkeys in the United States would have produced approximately 6Á5 and 18Á8 million tons of litter in 2015 respectively. Poultry litter, rich in macro- and micro-nutrients, has a great value as a soil amendment and organic fertilizer for agricultural production. Nonetheless, poultry litter is also the source of some human pathogens, such as Salmonella enterica (Chen and Jiang 2014). Poultry litter can be used in organic farming under certain conditions; however, under the Organic Materials Review Institute (OMRI)/USDA National Organic Pro- gram (NOP) rules and California Leafy Green Marketing Agreement, the use of raw manure on fresh produce that are intended for human consumption is discouraged due to the possible presence of human pathogens (Timmenga & Associates Inc. 2003; NOP 2006; California Leafy Green Handler Marketing Board 2010). Physically heat-treated Journal of Applied Microbiology 122, 1558--1569 © 2017 The Society for Applied Microbiology 1558 Journal of Applied Microbiology ISSN 1364-5072