Abstract
Enteric pathogens from biofertilizer can accumulate in the soil, subsequently contaminating water and crops. We evaluated the survival, percolation and leaching of model enteric pathogens in clay and sandy soils after biofertilization with swine digestate: PhiX-174, mengovirus (vMC0), Salmonella enterica Typhimurium and Escherichia coli O157:H7 were used as biomarkers. The survival of vMC0 and PhiX-174 in clay soil was significantly lower than in sandy soil (iT90 values of 10.520 ± 0.600 vs. 21.270 ± 1.100 and 12.040 ± 0.010 vs. 43.470 ± 1.300, respectively) and PhiX-174 showed faster percolation and leaching in sandy soil than clay soil (iT90 values of 0.46 and 2.43, respectively). S. enterica Typhimurium was percolated and inactivated more slowly than E. coli O157:H7 (iT90 values of 9.340 ± 0.200 vs. 6.620 ± 0.500 and 11.900 ± 0.900 vs. 10.750 ± 0.900 in clay and sandy soils, respectively), such that E. coli O157:H7 was transferred more quickly to the deeper layers of both soils evaluated (percolation). Our findings suggest that E. coli O157:H7 may serve as a useful microbial biomarker of depth contamination and leaching in clay and sandy soil and that bacteriophage could be used as an indicator of enteric pathogen persistence. Our study contributes to development of predictive models for enteric pathogen behavior in soils, and for potential water and food contamination associated with biofertilization, useful for risk management and mitigation in swine digestate recycling.
Highlights
Global demand for fertilizer nutrients, including nitrogen, phosphorus, and potassium, is expected to reach 200,500,000 tons by 2018, and food demand for human consumption and livestock feed is expected to increase by 60–110% by 2050
Whereas the time for a significant reduction in clay soils was similar for the two viruses selected in this study (40 days for vMC0 and 50 days for PhiX-174), the times were longer in sandy soils (60 days for vMC0, and no significant reduction of PhiX-174 after 120 days) (Figure 1)
The ıT90 values were higher in clay than in sandy soils for all the microorganisms (6.62 vs. 10.75 for E. coli O157:H7, 9.34 vs. 11.90 for S. enterica Typhimurium, 10.52 vs. 21.27 for vMC0, and 12.04 vs. 43.47 for PhiX-174) (Table 2)
Summary
Global demand for fertilizer nutrients, including nitrogen, phosphorus, and potassium, is expected to reach 200,500,000 tons by 2018, and food demand for human consumption and livestock feed is expected to increase by 60–110% by 2050. Swine digestate can contain high levels of enteric pathogens that may contaminate soil, water, and foods (Khetsuriani et al, 2006; Topp et al, 2009). Microbial models can be used to assess the behavior of enteric pathogens, including their survival, flow, propagation, leaching, percolation, and inactivation (Langlet et al, 2008; Boudaud et al, 2012) Bacteriophages, such as somatic coliphages (e.g., PhiX-174), f-specific RNA phages (e.g., MS2), and mengovirus (vMC0) have been used as models for human and animal enteric viruses (Langlet et al, 2008; Boudaud et al, 2012). Salmonella is one of the most prevalent bacterial pathogens; it is zoonotic and has high survival rates in environment (Griffith et al, 2006; Venglovsky et al, 2006; European Food Safety Authority, and European Centre for Disease Prevention, and Control, 2015)
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