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United States Department of Agriculture

Agricultural Research Service

2008 Annual Report

1a.Objectives (from AD-416)
Whole genomic analysis is currently revealing previously unknown evolutionary trends in Salmonella enterica subsp. I serovar Enteritidis (SE) that impact the ability of this pathogen to grow and colonize hens and to contaminate eggs ( The objective of this research is to determine critical genetic determinants that impact the ability of SE to contaminate the eggs of hens and to otherwise propagate in the poultry environment.

3.Progress Report

This project is related to Objective 2 of the in-house project: Determine how genetically defined strains of Salmonella enterica vary in their pathobiology within the hen and how these differences affect the risk of egg contamination and the control of disease.

Collaborator made available to USDA a Salmonella typhimurium culture that contained a mixed population of 940 mutants. The purpose of the research was to see which mutants could be recovered following infection of two different animal hosts, namely rodents and hens. USDA infected chickens with the culture and recovered organs in one trial, droppings in one trial, and intestinal sample in two trials. The collaborating laboratory infected mice and recovered samples, because "founder population" effects had to be surpassed in order to make the comparisons statistically valid and to detect mutants that survived and multiplied. An unexpected finding was that the rodent yielded high bacterial loads routinely exceeding the population threshold, whereas the chicken did not. The 2nd trial examing intestinal loads in chickens gave the same result. These results suggest that the chicken may be resistant to carrying high Salmonella loads as compared to the rodent. The result that the mouse might be a host that amplifies Salmonella on-farm substantiates the importance of efforts to control rodent populations to decrease egg contamination. These results were unexpected and require evaluation to see if they are complete enough for publication or if they should instead be used as the basis for further research. The collaborator was disappointed that the chicken did not yield high concentrations of Salmonella from intestinal contents and internal organs in comparison to the mouse and may not be inclined to pursue this avenue of research further. The USDA scientist thinks that the negative findings are perhaps meaningful for understanding why rodents on-farm are a recognized risk factor for egg contamination. Communications are in progress. The collaborator may allow USDA to use the mutant bank for purposes outside of the collaborator's scope of interest, but this will need to be documented in a Materials Transfer Agreement (MTA) that is outside the scope of the NFCA.

MONITORING ACTIVITIES: In August 2008 the collaborator was contacted for updates on what was going to be done with the data. Communications were maintained by email exchange and sharing of results by spreadsheet.

Last Modified: 11/30/2015
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