Influence of Poultry Litter Amendment Type and Irrigation Events on Survival and Persistence of Salmonella Newport

Abstract

Salmonella enterica subsp. enterica serovar Newport is a bacterial foodborne pathogen isolated from several environmental reservoirs on the Delmarva Peninsula and has been associated with several produce-related outbreaks. However, little is known about specific interactions between Salmonella Newport and soil amendments used as fertilizers. The purpose of this study was to determine Salmonella Newport persistence and resuscitation in raw poultry litter (PLR), a common biological soil amendment, and in soils containing poultry litter-based (heat-treated poultry pellets [HTPP]) or chemical fertilizer (urea [U]) amendments to provide equivalent levels of nitrogen to the soil. Inoculated samples were stored in a growth chamber and irrigated regularly over 4 weeks. Soil samples were collected every week for 4 weeks to determine moisture content and surviving Salmonella Newport populations (log CFU per gram dry weight). Data were analyzed by using a one-way analysis of variance and Student's t test. The PLR supported significantly higher (5.07 log CFU/g dry weight [gdw]) populations of Salmonella Newport than HTPP only (1.70 log CFU/gdw). However, PLR-amended (PRLA) soil (2.5 log CFU/gdw) samples had significantly (P < 0.05) lower Salmonella Newport populations compared with HTPP-amended (4.5 log CFU/gdw) and U-amended (4.0 log CFU/gdw) soil samples. The effect of irrigation on Salmonella Newport population levels in PRLA soils was significant, and in a comparative study, the overall increase in the pathogen levels in U-amended soil (mean = 1.12 log CFU/gdw) was significantly greater than that in PLRA soil (mean = 0.54 log CFU/gdw), whereas that in HTPP-amended soil (0.80 log CFU/gdw) was not significantly different from PLRA soil.