Risk of infection withSalmonella andEscherichiacoli O157:H7 due to consumption of lettuce in southern Brazil

Abstract

This study was carried out to estimate the risks of infection due to consumption of lettuce contaminated with these pathogens in Southern Brazil. The quantitative microbial risk assessment (QMRA) model comprised nine modules from storage of lettuce in producer farms until consumption. Scenarios were simulated using prevalence, concentration, and exposure levels lower than found in Brazil. Different procedures of washing and disinfection as well as cold chain (≤5ºC) in all distribution steps were also tested. Models built in Excel spreadsheet were simulated using @Risk® software. The QMRA simulations show that overall risks of foodborne disease due to consumption of lettuce are higher for Salmonella than for E. coli O157:H7. All alternative scenarios to clean lettuce, increase the risk (the best procedure was washing leaves with potable water followed by immersion in 200 ppm of sodium hypochlorite sanitizer for 15 minutes and rinsing with potable water). The major risk reduction was due to cold chain scenario. Sensitivity analyses indicated that in addition to the maintenance of the cold chain and the washing and disinfection procedures, it is important to reduce the prevalence and concentration of pathogens on lettuce in fields, in order to decrease the risk of infection by these bacteria.