The effect of heat-treated poultry pellets and composted poultry litter on E. coli survival in Southeastern US soils: Florida and Georgia

Authors: KHAREL, KARUNA - Louisiana State University; Bardsley, Cameron; APPOLON, CHARLES - University Of Florida; DUNN, LAUREL - University Of Georgia; DEV KUMAR, GOVINDARAJ - University Of Georgia; KRISHNA, PRABHA - University Of Georgia; SHARMA, MANAN - US Department Of Agriculture (USDA); DANYLUK, MICHELLE - University Of Florida; SCHNEIDER, KEITH - University Of Florida

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Soils used for growing produce can become contaminated with foodborne pathogens, which can lead to crop contamination during production. The use of composted and heat treated soil amendments, such as poultry manure and poultry litter, can improve soil fertility but may enhance the survival of pathogens like E. coli. This study evaluated the roles composted poultry litter, heat treated poultry pellets, location (Florida and Georgia), and weather parameters play on the survival of E. coli in agricultural soil. Heat treated poultry pellets prolonged the survival of E. coli compared to composted poultry litter and untreated soils in both Florida and Georgia. In Florida composted poultry litter increased E. coli survival compared to untreated soil. The weather or location did not have any effect on E. coli survival. This research shows that regardless of weather and location factors, poultry manure and heat treated poultry pellets increase the survival of E. coli. It is important to determine safe application of these types of amendments to prevent produce contamination.

Technical Abstract: 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 x 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 < 0.05) the survival of E. coli in soil. In FL, HTPP-amended soils supported higher levels of E. coli compared to PL-amended soils; in Georgia, similar survival was observed between PL- and HTPP-amended soils, both of which were higher (P < 0.05) than in UN soils. In both locations, E. coli levels fell to the limit of detection (-0.24 log MPN/g) by 112 d in UN plots; however, they persisted at levels between 0.30-1.57 log CFU/g in HTTP- and PL-amended soils until 140 d. Weak to moderate correlations were observed for rainfall and soil moisture and their effect on E. coli survival; no other weather factors were impactful. The use of BSAAO in soils can prolong the survival of E. coli (>140 d) irrespective of the factors intrinsic to the locations and have implications regarding the safe use of BSAAOs during fruit and vegetable production.