Listeria monocytogenes growth dynamics on produce: a review of the available data for predictive modeling

Several listeriosis outbreaks have been linked to the consumption of fresh or processed produce in recent years. One major determinant of the listeriosis risk is the ability of a food to support growth of Listeria monocytogenes during storage. However, data regarding the ability to support growth of L. monocytogenes are scarce or nonexisting for many produce commodities. Here we synthesize the available data regarding growth behavior of L. monocytogenes on produce, compare the growth data with listeriosis outbreak data, and evaluate the adequacy of the data for predictive modeling. Growth rates and maximum L. monocytogenes population densities differed markedly among produce commodities, and post-harvest processing had a considerable effect on growth dynamics for certain commodities such as tomatoes. However, data scarcity prevented reliable estimation of growth rates for many commodities. Produce outbreaks seemed frequently associated with processed produce and often involved storage under suboptimal conditions (e.g., at room temperature for several hours or for several months in the refrigerator) or environmental cross-contamination after processing. However, no clear associations between high growth rates of L. monocytogenes on fresh produce and outbreaks were detected. In conclusion, produce commodities differ in the supported growth rate of L. monocytogenes, the maximum attainable L. monocytogenes population density, and possibly in the impact of post-harvest processing, but data are currently insufficient to predict growth behavior, and the listeriosis risk appears to be also governed by additional factors.