Influence of poultry litter amendment type and irrigation events on survival and persistence of Salmonella newport

Authors: TECIHMANN, JUNE - University Of Delaware; LITT, PUSHPINDER - University Of Delaware; Sharma, Manan; NYARKO, ESMOND - University Of Delaware; KNIEL, KALMIA - University Of Delaware

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2019
Publication Date: 4/21/2020
Citation: Tecihmann, J., Litt, P.K., Sharma, M., Nyarko, E., Kniel, K.E. 2020. Influence of poultry litter amendment type and irrigation events on survival and persistence of Salmonella newport. Journal of Food Protection. 83: 821–828.

Interpretive Summary: Salmonella Newport has been a bacterial pathogen implicated in outbreaks of human illness associated with several produce commodities (tomatoes, cucumbers) in the Mid-Atlantic (Delmarva peninsula) region. Several studies have shown that Salmonella Newport is present in the agricultural environments (soils, surface waters) that may be important in the cultivation of fruits and vegetables in the Mid-Atlantic U.S. Organic fertilizers based on poultry litter are popular because of the target amount of nutrients they provide for plant growth. The objective of this work was to determine if chemical or poultry litter-based fertilizers could affect the levels of Salmonella Newport either in the fertilizer alone, or in soil / fertilizer mixtures. Raw poultry litter (PLR) supported higher levels of S. Newport over time compared to heat-treated poultry pellets (HTPP) over four weeks; however, when fertilizers were added to soils, HTTP-amended soils supported higher levels of S. Newport in PLR-amended soils over four weeks. This work shows that poultry litter-based fertilizers in soils can support S. Newport levels over a four-week period of time. This work benefits growers and regulators by showing that S. Newport persistence in soils is based on the type of fertilizer used in fruit and vegetable production.

Technical 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 S. Newport and soil amendments used as fertilizers. The purpose of this study is to determine S. Newport persistence and resuscitation in raw poultry litter (PLR), a common biological soil amendment, and in soils containing PL-based (heat-treated poultry pellets, HTPP) or chemical fertilizer (urea, U) amendments to provide equivalent levels of nitrogen to 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 S. Newport populations (log10 CFU/gdw (gram dry weight)). Data were analyzed using a one-way analysis of variance and student’s T-test. Mean S. Newport populations in PLR only (5.07 log10 CFU/gdw) was significantly greater than that in HTPP only (1.70 log10 CFU/gdw) over the same time-period. On the contrary, S. Newport populations in HTPP amended soil (4.5 log10 CFU/gdw) was comparable with that of urea (U) amended soil (4.0 log10 CFU/gdw), but both were significantly (p<0.05) greater than that in PLR amended soils (2.5 log10 CFU/gdw). The effect of irrigation on S. Newport population levels in poultry litter amended soils was significant, and in a comparative study, the overall increase in the pathogen levels in U-amended soil (mean = 1.12 log10 CFU/gdw) was significantly greater than that in PLR amended soil (mean = 0.54 log10 CFU/gdw), whereas that in HTPP amended soil (0.80 log10 CFU/gdw) was not significantly different from PLR amended soil.