Location: Egg Safety and Quality
Title: Multiplication of Salmonella Enteritidis in egg yolks after inoculation outside, on, and inside vitelline membranes and storage at different temperatures Authors
Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 5, 2010
Publication Date: July 15, 2010
Citation: Gast, R.K., Guraya, R., Guard, J.Y., Holt, P.S. 2010. Multiplication of Salmonella Enteritidis in egg yolks after inoculation outside, on, and inside vitelline membranes and storage at different temperatures. Poultry Science Association Meeting Abstract. (89): p. 856. Technical Abstract: Prompt refrigeration to restrict bacterial growth is a widely acknowledged practice for reducing the risk of egg-borne transmission of Salmonella Enteritidis to consumers. A recently published federal regulation for S. Enteritidis control requires eggs to be refrigerated within 36 after they are laid, but allows ambient temperature storage until this time limit is reached. Although the nutrient-rich interior of the yolk is a relatively infrequent location for initial S. Enteritidis deposition in naturally contaminated eggs, migration across the vitelline membrane can result in rapid bacterial multiplication inside eggs stored at warm temperatures. The objective of the present study was to measure the multiplication of S. Enteritidis in egg yolks after introduction at three different locations and subsequent storage at a range of temperatures. Using an in vitro egg contamination model, approximately 100 cfu of a phage type 13a strain of S. Enteritidis were inoculated either inside yolks, onto the exterior surface of vitelline membranes, or into the adjacent albumen. After storage of samples from each inoculation group at 10º, 15º, 20º, and 25º C for 24 h, S. Enteritidis was enumerated in yolks. For all three inoculation locations, the final S. Enteritidis levels in yolks increased significantly with increasing storage temperatures. At all storage temperatures, significant differences in S. Enteritidis multiplication were observed between inoculation sites (yolk inoculation > vitelline membrane inoculation > albumen inoculation). At 25º C, final log10 S. Enteritidis concentrations of 7.76 cfu/ml (yolk inoculation), 2.01 cfu/ml (vitelline membrane inoculation) and 0.76 cfu/ml (albumen inoculation) were attained in yolks after storage. These results demonstrate that, even when the initial site of S. Enteritidis deposition is outside the egg yolk, substantial multiplication supported by yolk nutrients can occur during the first day of storage and the risk of bacterial growth increases at higher ambient storage temperatures. This information highlights the importance of rapid refrigeration for protecting consumers from egg-transmitted illness.