Trials were conducted to compare surrogate organisms (PSO) to human pathogens (Salmonella spp. and Escherichia coli O157:H7) on the surface of orange fruit. Among the six evaluated PSO, E. coli ATCC 8739 and E. coli ATCC 35218 showed a significantly lower attachment (S-R) on fruit in comparison to Salmonella spp. In thermal tolerance studies, the D-70C values of the evaluated PSO were either no different from or greater than those of the pathogens. However, the D-80C of E. coli ATCC 25922 was significantly lower than that of the E. coli O157:H7. In general, E. coli ATCC 11229 exhibited a higher level of alkali sensitivity than both pathogens; whereas Lactobacillus plantarum ATCC 14917 and, to a lesser extent, Lactobacillus fermentum ATCC 538 showed a significantly greater tolerance to the alkali treatments. The results suggest that nonpathogenic cultures of E. coli ATCC 11229, L. fermentum ATCC 538, and L. plantarum ATCC 14917 may be utilized in fresh fruit research as surrogates for pathogens to evaluate the efficacy of thermal decontamination. In addition, E. coli ATCC 25922, L. fermentum ATCC 538, and L. plantarum ATCC 14917 cultures may be used to represent pertinent pathogens for validating fruit decontamination by alkaline cleaners.
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