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United States Department of Agriculture

Agricultural Research Service

Research Project: EGG PROCESSING SAFETY, QUALITY AND SECURITY

Location: Egg Safety and Quality

Title: Microbial Levels and Pathogen Prevalence Associated with Restricted Shell Eggs

Authors
item Jones, Deana
item Musgrove, Michael

Submitted to: Journal of Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: February 23, 2007
Publication Date: July 8, 2007
Citation: Jones, D.R., Musgrove, M.T. 2007. Microbial Levels and Pathogen Prevalence Associated with Restricted Shell Eggs (abstract). International Association of Food Protection 2007 Program and Abstract Book.p.99.

Interpretive Summary: Restricted shell eggs not meeting quality standards for retail, but maintaining acceptable quality for inclusion in further processed eggs, are often diverted to further processing. A study was conducted to characterize the microbiological populations present on and in these eggs. On a single day restricted eggs were collected from three shell egg processing plants a total of three times (replicates). Six shells or egg contents were combined to create a pool. Ten pools of each (shells and contents) were formed for each plant per replicate. Shells and membranes were macerated in sterile phosphate buffered saline. Contents were stomacher blended to form a homogeneous mixture. Total aerobic microorganisms and Enterobacteriaceae were enumerated. The prevalence of Salmonella, Campylobacter and Listeria were determined by cultural methods. Average aerobic counts associated with the shells were 4.3 log CFU/ml and 2.0 log CFU/ml for contents. There were plant*replicate differences for both types of aerobic samples (P < 0.05 and P < 0.01, respectively). Average Enterobacteriaceae level associated with the shell was 2.4 log CFU/ml and less than 0.1 log CFU/ml in the egg contents with 36.7 % of samples being positive. One shell sample (0.5 % of total samples) was Campylobacter positive. Two shell samples (1.1 % of total samples) were Salmonella positive. Twenty-one percent of samples were positive for Listeria (33 – shells; 5 – contents). While current pasteurization guidelines are based on Salmonella lethality, the results of this study indicate a need to revisit the guidelines to determine effectiveness for other pathogenic species.

Technical Abstract: Restricted shell eggs not meeting quality standards for retail, but maintaining acceptable quality for inclusion in further processed eggs, are often diverted to further processing. A study was conducted to characterize the microbiological populations present on and in these eggs. On a single day restricted eggs were collected from three shell egg processing plants a total of three times (replicates). Six shells or egg contents were combined to create a pool. Ten pools of each (shells and contents) were formed for each plant per replicate. Shells and membranes were macerated in sterile phosphate buffered saline. Contents were stomacher blended to form a homogeneous mixture. Total aerobic microorganisms and Enterobacteriaceae were enumerated. The prevalence of Salmonella, Campylobacter and Listeria were determined by cultural methods. Average aerobic counts associated with the shells were 4.3 log CFU/ml and 2.0 log CFU/ml for contents. There were plant*replicate differences for both types of aerobic samples (P < 0.05 and P < 0.01, respectively). Average Enterobacteriaceae level associated with the shell was 2.4 log CFU/ml and less than 0.1 log CFU/ml in the egg contents with 36.7 % of samples being positive. One shell sample (0.5 % of total samples) was Campylobacter positive. Two shell samples (1.1 % of total samples) were Salmonella positive. Twenty-one percent of samples were positive for Listeria (33 – shells; 5 – contents). While current pasteurization guidelines are based on Salmonella lethality, the results of this study indicate a need to revisit the guidelines to determine effectiveness for other pathogenic species.

Last Modified: 7/27/2014
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