Risk factors associated with the prevalence of Shiga-toxin-producing Escherichia coli in manured soils on certified organic farms in four regions of the USA

Introduction Biological soil amendments of animal origin (BSAAO), including untreated are often used to improve fertility and particularly important in organic agriculture. However, application manure on cropland can potentially introduce foodborne pathogens into the onto produce. Certified farms follow USDA National Organic Program (NOP) standards that stipulate a 90- or 120-day interval between crop harvest, depending whether edible portion directly contacts soil. This time-interval metric is based environmental factors does not consider multitude might affect survival main concern. The objective this study was assess predictors for prevalence Shiga-toxin-producing Escherichia coli (non-O157 STEC) soils amended with USDA-NOP certified farms. Methods A longitudinal, multi-regional conducted 19 four USA regions two growing seasons (2017–2018). Untreated (cattle, horse, poultry), soil, irrigation water samples were collected enrichment cultured non-O157 STEC. Mixed effects logistic regression models analyze STEC up 180 days post-manure application. Results discussion show farm management practices (previous use livestock, presence feces field, season application) characteristics (presence generic E. moisture, sodium) increased odds STEC-positive samples. Manure method snowfall decreased detecting Time-variant (year sampling day) affected shows single metric, such as time may be sufficient reduce food safety risks from manure, additional farm-management should also considered. These findings particular importance because they provide baseline data relating current NOP wait-time standards. They therefore contribute development strategies pathogen persistence contamination fresh produce typically eaten raw NOP-certified using manure.