Eggshell penetration of hen's eggs by Salmonella enterica serovar Enteritidis upon various storage conditions

1. The survival and penetration of Salmonella enterica serovar Enteritidis (SE) inoculated on the eggshell was examined upon storage for up to 20 d at real-life conditions (15 to 25 degrees C and 45 to 75% relative humidity (RH)). 2. Penetration was assessed by emptying the egg contents and filling the eggs with a selective medium that allowed visualising Salmonella growth on the inside of the shell and membrane complex. 3. The study of survival on the eggshells was based on viable counts and showed that numbers of surviving organisms decreased over time. Survival was inversely related to storage temperature and RH. Although the average counts decreased over time, a limited proportion of shells carried high numbers of SE at all storage conditions. 4. Penetration spots were observed earlier using an increased storage temperature due to increased growth rates of SE on the agar. After 20 d of storage a similar percentage (c. 44.7%) of eggshells became penetrated, irrespective of the storage conditions tested in this study. 5. The higher the Salmonella shell contamination at the end of storage, the higher the probability that the eggshell was penetrated. Salmonella shell counts exceeding 4 log cfu yielded more than a 90% probability of eggshell penetration occurring.