Submitted to: Western Poultry Disease Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2003
Publication Date: 3/30/2003
Citation: Bouldin, J.G., Gast, R.K., Humphrey, T.J., Henzler, D.J., Morales, C., Coles, K. 2003. Subpopulation behavior of egg-contaminating salmonella enterica serovar enteritidis as defined by lipopolysaccharide o chain. Western Poultry Disease Conference. Interpretive Summary: A serotype of Salmonella called Salmonella enteritidis is the only one that contaminates the hen egg and causes disease in humans. It is currently the leading cause of human salmonellosis worldwide and the second most common cause in the United States. This investigation reveals that the molecule called LPS O-chain changes within the infected animal as the bacteria reaches different sites. Salmonella enteritidis loses O-chain when isolated from organs such as the spleen, but gains it after recovery from the hen's reproductive tract organs and the egg. These results strongly suggest that Salmonella serotypes that result in outbreaks increase LPS O-chain in at least one organ group, namely internal organs or reproductive tract organs. Salmonella that are falsely positive for producing LPS O-chain when tested with traditional immunological methods rather than chemistry probably interfere with the understanding and control of one of our most important food borne pathogens.
Technical Abstract: Characterization of Salmonella enterica serovar Enteritidis was refined by incorporating new data from isolates obtained from avian sources, from the spleens of naturally infected mice, and from avian sources within the United Kingdom into an existing lipopolysaccharide (LPS) O-chain compositional database. The probabilities that avian isolates produced high-molecular-mass LPS O chain ranked, from least to greatest, as follows: pooled kidney, liver, spleen < intestine < cecum < ovary and oviduct < albumen < yolk < whole egg. Mouse isolates were most like avian intestinal samples, whereas United Kingdom isolates were most like avian reproductive tract and egg isolates. Non-reproductive tract organ isolates had significant loss of O-chain. Isogenic isolates whose abilities to make biofilm and to be orally invasive varied produced different O-chain structures at 25 but not at 37OC. Hens infected at a 91:9 biofilm-positive/biofilm-negative colony phenotype ratio yielded only the negative phenotype from eggs. These results indicate that the environment within the hen applies stringent selection pressure on subpopulations of S. enterica serovar Enteritidis at certain points in the infection pathway that ends in egg contamination. The avian cecum is an early interface between the environment and the host that supports emergence of subpopulation diversity, which suggests that diet and other factors that alter gut physiology could be manipulated to reduce egg contamination.