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Research note: growth of Salmonella enteritidis in Grade A eggs during prolonged storage
T S Hammack1, P S Sherrod, V R Bruce
1Division of Microbiology, U.S. Food and Drug Administration, Washington, District of Columbia 20204.
Abstract:
Migration of Salmonella enteritidis through egg albumen to the yolk and its subsequent growth in the yolk were examined. Submersion of eggs in .1% mercuric chloride solution for 1 h followed by submersion in 70% ethanol for 30 min resulted in an eggshell surface from which no Salmonella organisms were recovered. The eggs were then inoculated with S. enteritidis under the shell membrane. Although growth of S. enteritidis was negligible in eggs refrigerated up to 16 days, the population level of the organism increased by more than 8 log10 units in unrefrigerated eggs stored for the same amount of time.
Insights
Salmonella enteritidis contamination in eggs is reduced by surface disinfection. Refrigeration significantly inhibits Salmonella growth in eggs, while unrefrigerated storage promotes substantial bacterial proliferation.
Area of Science:
- Food safety
- Microbiology
- Food science
Background:
- Salmonella enteritidis is a significant foodborne pathogen.
- Eggs are a common vehicle for Salmonella transmission.
- Understanding Salmonella migration and growth in eggs is crucial for food safety.
Purpose of the Study:
- To investigate the migration of Salmonella enteritidis from the eggshell to the yolk.
- To assess the growth of Salmonella enteritidis within the egg yolk.
- To evaluate the efficacy of surface disinfection and refrigeration on Salmonella contamination in eggs.
Main Methods:
- Eggs were surface-disinfected using mercuric chloride and ethanol solutions.
- Salmonella enteritidis was inoculated under the eggshell membrane.
- Bacterial populations were enumerated in eggs stored under refrigerated and unrefrigerated conditions for 16 days.
Main Results:
- Surface disinfection effectively eliminated detectable Salmonella from the eggshell.
- Salmonella enteritidis showed negligible growth in refrigerated eggs.
- A significant increase (over 8 log10 units) in Salmonella enteritidis population was observed in unrefrigerated eggs.
Conclusions:
- Proper eggshell disinfection can prevent initial Salmonella contamination.
- Refrigeration is critical for inhibiting Salmonella enteritidis growth in eggs.
- Improper storage conditions (i.e., unrefrigerated) can lead to dangerous levels of Salmonella proliferation in eggs.