Mild food processing could trigger stress response, or even elevated virulence, in the targeted pathogen. Such conditions could be encountered during improper pasteurization of shell eggs. Hence, changes in the virulence of Salmonella enterica serovar Enteritidis, driven by sublethal processing of shell eggs, were investigated. Shell eggs were inoculated with ∼103 CFU Salmonella Enteritidis/egg and incubated to a pathogen's population of ∼109 CFU/egg. These eggs were heated to an internal temperature of 42 °C, applied alone or followed by a 30-min ozone exposure (7.5 %, wt./wt. ozone in ozone-oxygen mixture), to mimic egg sub-pasteurization conditions. Levels of Salmonella Enteritidis were standardized in yolk of processed or untreated eggs (3.4–3.7 log CFU/mL) and 200 μL of the standardized yolk were orally administered in streptomycin-treated C57BL/6 mice. On day one post-infection, mice that received the heat–ozone treated yolk exhibited faster Salmonella colonization compared to those received heated-only or untreated yolk, but on day four, pathogen's fecal populations did not differ significantly (p > 0.05) among the three groups. On day five post-infection, populations of Salmonella Enteritidis were not significantly different (7.7–7.9 log CFU/g; p > 0.05) in ceca of mice of the three treatment groups; however, histological examination revealed considerable elevation of colonic inflammation in mice receiving the processed yolk, relative to the untreated yolk. These findings suggest that sub-pasteurization treatments compromises egg safety by elevating Salmonella virulence and consequently increasing the risk of Salmonella infection. Hence, the results emphasize the need for careful implementation of egg pasteurization methods.
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