The Effect of Heat-treated Poultry Pellets and Composted Poultry Litter on E. coli Survival in Southeastern US Soils: Florida and Georgia

Biological soil amendments of animal origin (BSAAO) are a source of foodborne pathogens that can contaminate fresh produce. This study evaluated the survival of E. coli over 140 d in agricultural soils amended with composted poultry litter (PL), heat-treated poultry pellets (HTPP), or unamended (UN) in Florida (FL) and Georgia (GA). Raised-bed plots (1 × 3 m2; n = 3) were either left unamended (UN) or amended with PL or HTPP (680 g/plot). Each plot was spray-inoculated with 1 L of rifampicin-resistant E. coli (7–8 log CFU/mL) and hand-tilled into the soil (∼5.9 and 4.5 log CFU/g for FL and GA, respectively). Soil samples were enumerated using a spread plate or most probable number technique at 0, 1, 3, 7, 14, 28, 56, 84, 112, and 140 d. Weather-related parameters were collected to assess their impact on E. coli survival. A mixed-model analysis was used to evaluate factors influencing E. coli survival, a biphasic model was used for the E. coli die-off rate, and Spearman correlations were used to understand the associations between environmental factors and survival. Time, amendment type, and location * treatment * time influenced (P