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ARS Home » Research » Research Project #421227



2013 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:
A commercial facility was modified to include 3 types of housing systems for laying hens (traditional cages, aviaries, and enriched cages), and environmental samples were collected from each type of housing. Areas sampled included egg belts, cage wiring, manure belts, egg ramps/elevators, nest area, roosts, and drag swabs of floors. Flies and rodents were sampled intermittently.Total aerobic microorganisms and Enterobacteriaceae were enumerated in these environmental samples and the presence of Salmonella and Campylobacter was determined by selective enrichment. Salmonella and Campylobacter recovery was similar for traditional and aviary systems and lowest in enriched systems. After the last monthly samples were collected and the flocks were depopulated, the houses were re-sampled to determine the efficacy of cleaning procedures. Pathogens were not recovered after disinfection procedures were performed. Environmental and egg samples were collected from an associated egg processing facility. Environmental samples included rollers, trays, transport equipment (spindles and belts), brushes, tank drains, and egg waste buckets. None of the environmental swab samples were positive for Salmonella or Campylobacter and overall bacterial counts were low. Pooled egg slurry prepared from unwashed eggs laid by traditionally caged hens was positive for Salmonella, but no pathogens were recovered from washed eggs from any housing type (including floor eggs from the aviary system). Environmental and egg wash water samples were tested from another egg processing facility. Temperature and pH readings were recorded for wash water. The environmental samples most likely to yield positive results for Salmonella were drains, farm belts, accumulator belts, packer head brushes, clam shells, accumulator belts, and wash tanks. Eggs designated for breaker facilities were more likely to be contaminated than those intended for retail sale as shell eggs. Salmonella prevalence was highest when wash water pH was below 10.5.

4. Accomplishments