Temporal and Agricultural Factors Influence Escherichia coli Survival in Soil and Transfer to Cucumbers

Abstract

Biological soil amendments of animal origin (BSAAO) increase nutrient levels in soils to support production of fruits and vegetables. BSAAOs may introduce or extend survival of bacterial pathogens which can transfer to fruits and vegetables to cause foodborne illness. Escherichia coli survival over 120 days in soil plots (3m2) covered with (mulched) or without plastic mulch (not mulched), amended with either poultry litter, composted poultry litter, heat treated poultry pellets, or chemical fertilizer and transfer to cucumbers in two years (2018, 2019) was evaluated. Plots were inoculated with E. coli (8.5 log CFU/m2) and planted with cucumber seedlings (Supremo). The number of days (d) needed to reduce E. coli levels by 4 log CFU (dpi4log) was determined using a sigmoidal decline model. RandomForest regression and one-way ANOVA (p < 0.05) identified predictors (soil properties and nutrients, weather factors) of dpi4log of E. coli and transfer to cucumbers. The combination of year, amendment and mulch (25.0%IncMSE) and year (9.75%IncMSE) were the most prominent predictors of dpi4log and transfer to cucumbers, respectively. Nitrate levels at 30d and soil moisture at 40d were also impactful predictors of dpi4log. Differing rainfall amounts in 2018 (24.9 in) and 2019 (12.6 in) affected E. coli survival in soils and transfer to cucumbers. Salmonella spp. were recovered sporadically from various plots, but were not recovered from cucumbers in either year. Greater transfer of E. coli to cucumbers was also shown to be partially dependent on dpi4log of E. coli in plots containing BSAAO. IMPORTANCE Poultry litter and other biological soil amendments are commonly used fertilizers in fruit and vegetable production and can introduce enteric pathogens like E. coli O157:H7 or Salmonella previously associated with outbreaks of illness linked to contaminated produce. E. coli survival duration in soils covered with plastic mulch or uncovered and containing poultry litter, heat-treated poultry litter pellets were evaluated. Nitrate levels on day 30 and moisture content in soils on day 40 on specific days were good predictors of E. coli survival in soils; however, knowledge of the combination of year, amendment and mulch type was a better predictor. Different cumulative rainfall totals from year to year most likely affected the transfer of E. coli from soils to cucumbers and survival durations in soil. E. coli survival in soils can be extended by the addition of several poultry litter based soil amendments commonly used in organic production of fruits and vegetables and is highly dependent on temporal variation in rainfall.

Prevalence and Antimicrobial Resistance Profiles of Foodborne Pathogens Isolated from Dairy Cattle and Poultry Manure Amended Farms in Northeastern Ohio, the United States

“…The agricultural soil may naturally contain pathogenic bacteria or receive them during soil amendment using animal manure [ 28 ]. Soil amendment with animal manure increases crop yield, but it can potentially increase the spread of foodborne pathogens and ARGs in the environment [ 29 , 30 , 31 ]. Therefore, the USA Food and Drug Administration has recently limited the use of antimicrobials on farms in the USA due to the growing impact of antibiotic resistance in clinical practice and to reduce the selection pressure on the emergence of resistance bacteria [ 32 , 33 ].…”

Escherichia coli isolates from vegetable farms in Addis Ababa, Ethiopia: Antimicrobial susceptibility profile and associated resistance genetic markers

“…In our study, we did not measure the concentration of antibiotics in the collected samples, but different studies showed that antimicrobials were detected in agricultural soil amended with animal manure (Gros et al., 2019 ; Srichamnong et al., 2021 ). Thus, soil amendment with animal manure can potentially increase the selection and spread of resistant bacteria (Litt et al., 2021 ). In this study, E. coli isolates from soil showed a high rate of resistance to ampicillin, gentamicin, kanamycin, and sulfisoxazole, compared to manure and vegetable samples.…”

Persistent Spatial Patterns of Listeria monocytogenes and Salmonella enterica Concentrations in Surface Waters: Empirical Orthogonal Function Analysis of Data from Maryland

“…Salmonella enterica levels in water may be affected by agricultural practices such as using untreated manure as organic fertilizer, contributing to contaminated runoff to water bodies [48]. Other reports have shown that soil runoff containing organic fertilizers (heat-treated poultry pellets) can support Salmonella growth in water [49], and that soils amended with synthetic and heat-treated or composted organic fertilizers were contaminated with Salmonella as well [50]. In addition to the agricultural land use proximate to MA05, there was also relatively high wetlands land cover (17.7%), which may support wildlife (including avian, amphibian, and reptile populations), and these animals are known contributors to the S. enterica burden in this stream [51,52].…”