Biological soil amendments can support survival of pathogenic and non-pathogenic Escherichia coli in soils and sporadic transfer to Romaine lettuce
Date
2025-03-07
Journal Title
Journal ISSN
Volume Title
Publisher
International Journal of Food Microbiology
Abstract
Biological soil amendments (BSAs) are essential agricultural inputs that provide critical nutrients in organic leafy green production. Heat-treated poultry pellets (HTPP) and seabird guano (SBG), which have been treated to reduce microbial pathogen loads, are gaining popularity among growers. Using these BSAs in the process of side-dressing, providing nutrients to crops while growing, may provide opportunities for externally introduced bacterial pathogens to survive in soil. In this study, Romaine lettuce was grown in soils in a controlled environmental growth chamber. Soils were side-dressed twice with different combinations of treated BSAs: HTPP, SBG, and corn steep liquor (CSL). Soils were co-inoculated with non-pathogenic E. coli and two E. coli O157:H7 strains at the second of two side-dressing events. Survival of E. coli in soils over 28 days was evaluated. On day 28 post inoculation, two heads of Romaine lettuce from each planter were harvested, and the presence of E. coli on leaves was determined. Four nonlinear statistical models were fit to predict survival of E. coli in soils. In all soils regardless of BSA treatment, E. coli TVS 353 declined by 4.08–4.51 log CFU/g soil over 28 days, and E. coli O157:H7 declined by 2.77–4.3 log CFU/g soil over 28 days. E. coli TVS 353 and O157:H7 were recovered from 13.3 % (6/45) and 11.1 % (5/45) of plants, respectively. Transfer of E. coli from soils to Romaine lettuce was low, sporadic, and could not be measured quantitatively. Side-dressing with treated BSAs used in organic lettuce production supported but did not enhance survival of E. coli in side-dressed soils under controlled environmental conditions.
Highlights
• Soils were amended with BSAs to grow Romaine lettuce in environmental chambers.
• Some treated BSAs facilitated a rapid decline of E. coli O157:H7 in soils.
• Treated BSAs supported but did not enhance survival of E. coli in soils.
• Transfer of E. coli from soils to lettuce was low and sporadic.
Description
This article was originally published in International Journal of Food Microbiology. The version of record is available at: https://doi.org/10.1016/j.ijfoodmicro.2025.111147.
Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Keywords
biological soil amendments, E. coli O157:H7, preharvest produce safety, organic production, side-dressing
Citation
Xiong, Zirui Ray, Ellen Gabriel, Alan Gutierrez, Cheryl East, Kalmia E. Kniel, Michelle D. Danyluk, Michele Jay-Russell, and Manan Sharma. “Biological Soil Amendments Can Support Survival of Pathogenic and Non-Pathogenic Escherichia Coli in Soils and Sporadic Transfer to Romaine Lettuce.” International Journal of Food Microbiology 434 (April 16, 2025): 111147. https://doi.org/10.1016/j.ijfoodmicro.2025.111147.