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United States Department of Agriculture

Agricultural Research Service

Title: Recovery of Salmonella from Commercial Shell Eggs by Shell Rinse and Shell Crush Methodologies

Authors
item Musgrove, Michael
item Jones, Deana
item Northcutt, Julie
item Harrison, M - UGA
item Cox, Nelson
item Ingram, Kimberly
item Hinton, Jr, Arthur

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 20, 2005
Publication Date: July 29, 2005
Citation: Musgrove, M.T., Jones, D.R., Northcutt, J.K., Harrison, M.A., Cox Jr, N.A., Ingram, K.D., Hinton Jr, A. 2005. Recovery of salmonella from commercial shell eggs by shell rinse and shell crush methodologies. Poultry Science. 84(12):1955-1958.

Interpretive Summary: Salmonella is the most important human pathogen associated with shell eggs. Many methods are available for recovering Salmonella from egg shells and membranes. A study was conducted in which a shell rinse method and another method, crushing of shells and membranes together, were both used to recover Salmonella from commercial shell eggs. Eggs were collected at various stages of processing from three commercial shell egg processing plants in the Southeastern United States. Each plant was visited three times. A total of 394 pooled samples were analyzed in the course of the study. Overall there were 10.1% Salmonella positive samples (40/394). Overall, slightly more samples were detected by the crush method than the rinse method. Washed eggs were twice as likely to be Salmonella positive as unwashed eggs (15.8% v 8.3%). When wash water conditions were optimal (temperature > 42 C, pH > 10.4), the crush method was a superior means of recovering Salmonella. Though rinsing eggs is an easier method to perform, the crush method was more sensitive. This information will be used by researchers from industry or academia as well as by regulatory agencies as they conduct studies to determine how commercial shell egg washing affects Salmonella populations associated with shell eggs.

Technical Abstract: Salmonella is the most important human pathogen associated with shell eggs. Salmonella Enteritidis is the serotype most often implicated in outbreaks, though other serotypes have been recovered from eggs and from the commercial shell egg washing environment. Many sample methods are used to recover microorganisms from eggshells and membranes. A shell rinse and modified shell/membrane crush method for recovery of Salmonella were compared. Eggs were collected from three commercial shell washing facilities (X, Y, Z) during three visits. Twelve eggs were collected from each of 10-12 locations along the egg processing chain. After being transported back to the laboratory, each egg was sampled first by a shell rinse method and then by a shell crush method. For each technique (rinse or crush), two five-egg pools per location sampled were selectively enriched for the recovery of Salmonella. Presumptive Salmonella positives were confirmed serologically. Overall, there were 10.1% (40/396) Salmonella-positive pooled samples. Salmonella were recovered by the shell rinse and by the shell crush technique (4.8% v. 5.3%, respectively). Plant X yielded 21.5% Salmonella positives while less than 5% of samples from plants Y and Z were found to be contaminated with the organism (4.2% and 4.5%, respectively). Salmonella was recovered more often from unwashed eggs (15.8%) than from washed eggs (8.3%). For some eggs, Salmonella was only recovered by one of the methods. Using both approaches in the same experiment increased sampling sensitivity, though in most cases crushing, provided the more sensitive Salmonella recovery.

Last Modified: 11/28/2014
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