Salmonella Survival in Soil and Transfer Onto Produce via Splash Events

Abstract

Nearly one-half of foodborne illnesses in the United States can be attributed to fresh produce consumption. The preharvest stage of production presents a critical opportunity to prevent produce contamination in the field from contaminating postharvest operations and exposing consumers to foodborne pathogens. One produce-contamination route that is not often explored is the transfer of pathogens in the soil to edible portions of crops via splash water. We report here on the results from multiple field and microcosm experiments examining the potential for Salmonella contamination of produce crops via splash water, and the effect of soil moisture content on Salmonella survival in soil and concentration in splash water. In field and microcosm experiments, we detected Salmonella for up to 8 to 10 days after inoculation in soil and on produce. Salmonella and suspended solids were detected in splash water at heights of up to 80 cm from the soil surface. Soil-moisture conditions before the splash event influenced the detection of Salmonella on crops after the splash events—Salmonella concentrations on produce after rainfall were significantly higher in wet plots than in dry plots (geometric mean difference = 0.43 CFU/g; P = 0.03). Similarly, concentrations of Salmonella in splash water in wet plots trended higher than concentrations from dry plots (geometric mean difference = 0.67 CFU/100 mL; P = 0.04). These results indicate that splash transfer of Salmonella from soil onto crops can occur and that antecedent soil-moisture content may mediate the efficiency of microbial transfer. Splash transfer of Salmonella may, therefore, pose a hazard to produce safety. The potential for the risk of splash should be further explored in agricultural regions in which Salmonella and other pathogens are present in soil. These results will help inform the assessment of produce safety risk and the development of management practices for the mitigation of produce contamination. HIGHLIGHTS

Factors Associated With E. coli Levels in and Salmonella Contamination of Agricultural Water Differed Between North and South Florida Waterways

“…Agricultural water used in produce production environments has been identified as a probable route of contamination in past produce outbreaks (Greene et al, 2008;Klontz et al, 2010;Park et al, 2012;Rodrigues et al, 2020). When agricultural water comes into contact with the harvestable portion of a plant during production (e.g., during foliar irrigation, frost protection) or farm environment (e.g., through splash from contaminated soil and feces) fresh produce can become contaminated by human pathogens present in the water (Miles et al, 2009;Erickson et al, 2010;Fatica and Schneider, 2011;Ijabadeniyi et al, 2011;Atwill et al, 2015;Jeamsripong et al, 2019;Lee et al, 2019). Understanding pathogen ecology in freshwater environments used for produce production is critical for ensuring safety and assessing the risk of potential contamination events.…”

Effect of Weather on the Die-Off of Escherichia coli and Attenuated Salmonella enterica Serovar Typhimurium on Preharvest Leafy Greens following Irrigation with Contaminated Water

“…Several studies have investigated the survival and die-off of attenuated enterohemorrhagic E. coli (EHEC) and nonpathogenic E. coli ( 24 – 41 ) and Salmonella ( 32 , 35 , 42 ) on in-field leafy greens. For instance, Moyne et al ( 37 ) irrigated in-field lettuce with water contaminated with attenuated E. coli O157:H7 in 3 replicated trials in Salinas, CA, and observed a 2- to 3-log 10 reduction within 2 h of inoculation.…”

Role played by the environment in the emergence and spread of antimicrobial resistance (AMR) through the food chain

“…Dust containing antimicrobial residues or ARB can be emitted from livestock units or dried spread manure (Hamscher and Hartung et al, 2008;McEachran Andrew et al, 2015;Schulz et al, 2019) and can therefore represent an additional transmission route. The same holds true for soil particles that can be splashed up onto produce (Lee et al, 2019). Run-off from adjacent, fertilised or grazed fields may also move faecally contaminated soil particles to fresh produce (Barrios et al, 2020).…”