Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2000
Publication Date: 6/1/2001
Citation: Gast, R.K., Holt, P.S. 2001. Multiplication in egg yolk and survival in egg albumen of salmonella enteritidis strains of phage types 4, 8, 13a and 14b. Journal of Food Protection.
Interpretive Summary: Refrigerating eggs to temperatures at which bacterial growth cannot proceed has been widely recommended as a strategy for reducing the likelihood that contaminated eggs will transmit Salmonella enteritidis infection to humans. The present study used experimentally contaminated preparations of liquid egg components to determine whether 12 S. enteritidis strains (representing g4 different phage types) differed in their abilities to grow rapidly in eg yolk and to survive for several days in egg albumen. When very small numbers of S. enteritidis were introduced into yolk, they multiplied to reach mean levels of 1000 cells per ml within 6 hours of incubation at 25 C and mean levels of 100 million cells per ml within 24 hours. When larger initial numbers of S. enteritidis were introduced into albumen, bacterial levels remained nearly constant through 72 hours of incubation at 25 C. Although a few differences were observed between individual S. enteritidis strains, the overall multiplication and survival patterns were similar for all 12 isolates and no significant differences were evident between the four phage types. These results suggest that refrigeration standards may not need to address much potential variability between S. enteritidis strains, but preventing disease transmission by eggs will likely require rapid refrigeration in combination with other control measures.
Technical Abstract: Refrigeration of eggs is vital for restricting the multiplication of Salmonella enteritidis contaminants, but differences between S. enteritidis strains or phage types in their survival and multiplication patterns in egg contents might influence the effectiveness of refrigeration standards. The present study compared the abilities of 12 S. enteritidis isolates of four phage types (4, 8, 13a, and 14b) to multiply rapidly in egg yolk and to survive for several days in egg albumen. The multiplication of very small numbers of S. enteritidis inoculated into yolk (approximately 10 CFU/ml) was monitored during 24 hours of incubation at 25 C and the survival of much larger numbers of S. enteritidis inoculated into albumen (approximately 100,000 CFU/ml) was similarly evaluated during the first 3 days of incubation at the same temperature. In yolk, the inoculated S. enteritidis strains multiplied to mean levels of approximately 1000 CFU/ml after 6 h of incubation and 100,000,000 cells/ml after 24 hours. In albumen, mean levels of approximately 10,000 or more S. enteritidis CFU/ml were maintained through 72 hours. Although a few differences in multiplication and survival were observed between individual isolates, the overall range of values was relatively narrow and no significant differences were evident between phage types.