Risk assessment for Listeria monocytogenes on lettuce from farm to table in Korea

The risk of listeriosis due to the consumption of lettuce contaminated by Listeria monocytogenes, a foodborne pathogen with high fatality rate, was estimated using quantitative risk assessment model based on microbiological risk assessment principles and guidelines provided by Codex Alimentarius Commission. The whole food chain of lettuce from farm to table including initial contamination on the farm, growth and cross contamination during transportation, storage and consumption was simulated employing @Risk software and the results showed mean final contamination levels of −1.50 log CFU/g and −0.146 log CFU/g by L. monocytogenes at restaurant and home, respectively. The average number of annual cases in Korea estimated by the quantitative risk assessment model ranged from 559 to 817 based on the different r-values employed in the exponential dose–response model, which means the incidence of listeriosis ranged from 11.9 to 17.4 cases per million persons. Compared to the reported data in some developed countries, the derived results are overestimated. However, the QRAM in this study was conservatively developed, and it was calculated assuming the maximum-dose level as 7.5 log CFU/serving which meant that the worst cases were considered. ► Prevalence of L. monocytogenes on lettuce in Korea was determined. ► Lettuce distribution chain from farm to table was investigated. ► Cross contamination during transportation, storage and consumption was investigated. ► Washing step was necessary to mitigate the risk of L. monocytogenes in lettuce.