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United States Department of Agriculture

Agricultural Research Service

Research Project: INTERVENTION AND PROCESSING STRATEGIES FOR FOOD-BORNE PATHOGENS IN SHELL EGGS
2012 Annual Report


1a.Objectives (from AD-416):
1. Evaluate bactericidal effects of critical processing parameters (e.g. influence of wash water parameters, sanitizers, and sanitizer application methods) on egg safety. Specifically, conduct research on effective sanitizers (chemical, UV, etc.) and parameters that influence efficacy (temperature, nozzle type, etc.): 1.A Determine role of pH in wash water; 1.B Test chemicals as post-wash sanitizers for shell eggs; 1.C Evaluate modifications in post-wash sanitizer delivery.

2. Identify intervention strategies and processing practices for shell egg facilities and equipment that will improve sanitation standard operating procedures and reduce foodborne pathogens: 2.A Identify important reservoirs of Salmonella contamination in the processing environment; 2.B Evaluate sanitation interventions.

3. Develop more sensitive methods of detection and analysis and apply them in the determination and characterization of pathogen flow through the processing environment and onto eggs: 3.A Evaluate rapid, sensitive methods for pathogen detection; 3.B Utilize enhance methods to determine effect of housing on egg microbiology; 3.C: Characterize isolates at the molecular level to demonstrate flow from production through processing.


1b.Approach (from AD-416):
This project will promote egg safety by improving processing and intervention strategies in three critical areas. First, the bactericidal effects of critical processing parameters will be determined. Commercial egg wash detergents do an excellent job of cleaning eggs but are less lethal to bacteria when wash water pH is <10. Currently, the sanitizing chlorine solution sprayed onto eggs after washing does not reduce bacterial numbers. Research is needed to document the importance of pH and to identify an effective post-wash egg sanitizer. Second, improved sanitation procedures within processing facilities will be developed. Producing safe food requires a clean processing environment. Documentation is needed of areas and equipment in the processing facility most often contaminated with Salmonella. Such information will assist in development of effective means of removing or killing harmful bacteria. Third, better methods for detecting pathogens in egg processing environments and eggs will be developed. A recent new law requires egg producers to test for Salmonella Enteritidis (SE) in houses and flocks. Rapid, objective tests specific for SE will enable the egg industry in complying with this rule. Analyzing DNA from Salmonella collected at farms, processing facilities, and eggs allow for tracking of important contamination sources. Also, improved testing methods are required for a scientifically-based assessment of how different housing types affect egg microbiology.


3.Progress Report:
After preliminary sampling of a single facility the samples most likely to yield Salmonella positives were determined: drains, farm belts, accumulator belts, packer head brushes, clam shells, accumulator belts, and wash tanks. Eggs designated for breaker facilities are more likely to be contaminated than those for retail shell eggs. It is also important to take wash water temperature and pH measurements. It was observed that Salmonella prevalence was highest when pH was below 10.5.

Contact was made with a company that produces a chlorine adjuvant. This compound increases the pH range of effectiveness and also minimizes the effect of organic matter in inactivating chlorine compounds. This compound will be used in testing egg sanitizing before and after washing.

Escherichia coli cultures isolated from shell eggs were sent to a collaborator at the University Of Minnesota Medical School. These cultures are being analyzed and compared to clinical isolates implicated in human disease.

The first production cycle was completed for hens in traditional cages, aviary, and enriched cages. Monthly sampling was completed on eggs and environmental samples from each type of housing to determine effects of housing on microbiological impact. Aerobic microorganisms and Enterobacteriaceae were enumerated while samples were enriched for Salmonella and Campylobacter. Salmonella and Campylobacter recovery was similar for traditional and aviary systems and lowest in enriched systems.

On a quarterly basis, the same populations were monitored for washed eggs and for processing facility environmental samples. Counts and pathogen prevalence were low for environmental samples after eggs were washed. No pathogens were recovered from washed eggs regardless of housing type, including floor eggs from the aviary system.

After the last monthly samples were collected in June, the houses were re-sampled to determine the efficacy of cleaning procedures. As houses were depopulated no eggs were sampled. Pathogens were not recovered after disinfection procedures were performed.


4.Accomplishments
1. Effects of housing on egg microbiology. While the layer hen production environment is known to contribute to the microbial quality of shell eggs, it is more important to consider any residual effects after processing has been completed. Eggs from traditional cages, aviary, enriched cages, and eggs from the floor of aviary housing were sampled before and after processing (washed as required for retail shell eggs). None of the washed eggs was contaminated with Salmonella or Campylobacter and counts for aerobic microorganisms and Enterobacteriaceae were very low. This indicates that the commercial process is sufficient for decreasing shell contamination of eggs, regardless of where they are collected. Including floor eggs for shell egg producers that use an aviary style of housing can add to profits. This data shows that there is not a significant effect to shell egg safety based on housing.


Review Publications
Musgrove, M.T., Northcutt, J. 2012. Evaluation of an alcohol-based sanitizer spray's bactericidal effects on Salmonella inoculated onto stainless steel and shell egg processing equipment. International Journal of Poultry Science. 11(2):92-95.

Last Modified: 11/26/2014
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