ARS | Publication request: Penetration of Salmonella enteritidis through the yolk membrane in eggs from six genetically distinct commercial lines of laying hens.

Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2009
Publication Date: July 20, 2009
Citation: Gast, R.K., Jones, D.R., Anderson, K.E., Guraya, R., Bouldin, J.G., Holt, P.S. 2009. Penetration of Salmonella enteritidis through the yolk membrane in eggs from six genetically distinct commercial lines of laying hens. Poultry Science Association Meeting Abstract.

Technical Abstract: Infected laying hens can deposit Salmonella enteritidis inside developing eggs and thereby transmit disease to humans. Although deposition of S. enteritidis inside yolks is less common than deposition in the albumen or on the yolk (vitelline) membrane in naturally contaminated eggs, migration across the membrane to reach the nutrient-rich yolk contents could lead to extensive bacterial multiplication. Previous studies using in vitro egg contamination models determined that penetration into yolks to produce significant growth can occur during storage at warm temperatures, but not when eggs are refrigerated. The present study used an in vitro egg contamination model to assess the ability of small numbers of S. enteritidis to penetrate the vitelline membrane and multiply inside yolks of eggs laid by six genetically distinct commercial lines of hens during 24 hours of storage at 30 C. Eggs from each line were tested at four different hen ages by inoculation of approximately 100 cfu of S. enteritidis onto the outside of the vitelline membranes of intact yolks in plastic centrifuge tubes and then adding back the albumen into each tube before incubation. Overall, the frequency of penetration of S. enteritidis into the yolk contents of eggs from individual lines of hens ranged from 30% to 58% and the mean concentration of S. enteritidis in yolk contents after incubation ranged from 0.8 to 2.0 log10 cfu/ml. For both of these parameters, values for one hen line were significantly higher than for two other lines, but no other differences were observed. Hen age did not have a significant effect on egg yolk penetration by S. enteritidis. These results indicate that opportunities for the migration and growth of small initial numbers of S. enteritidis to attain more dangerous levels inside contaminated eggs during storage at warm temperatures can vary with different lines of laying hens.