Safety risks associated with dispersal of E. coli O157:H7 in home sprouting modules

Despite numerous outbreaks of foodborne illnesses associated with sprouts, consumption of raw sprouted seeds is still linked with a healthy lifestyle in Scandinavia. Different types of sprouting modules for home sprout production are available on the market, and sold without information about risks associated with sprouting. During sprouting, conditions are ideal for seed emergence, but also for bacterial proliferation. Moreover, since seeds used for sprouting are non-sterile, human pathogens may propagate within sprouting modules. This study assessed vertical dispersal of Escherichia coli strain O157:H7 in two types of three-layered sprouting modules intended for home sprouting. Organic fenugreek seeds were artificially inoculated and transferred to either the top or bottom layer of sprouting modules. As commensal bacterial biota can affect survival of an artificially introduced strain, but can also contain pathogens, culturable bacterial species on fenugreek seeds were evaluated. A Beta-Poisson model was used to assess the risk of consumer exposure to the artificially introduced strain when added to seeds in the top or bottom layer. We found that the inoculated strain dispersed vertically up and down between the layers and that the risk of bacterial dispersal was high in either direction, posing a high risk of consumer exposure.