Submitted to: Genbank
Publication Type: Other
Publication Acceptance Date: December 7, 2005
Publication Date: December 30, 2005
Citation: Bouldin, J.G., Morales, C. 2005. Genbank submissions dq231427-population set B. Available: http://www.ncbi.nlm.nih.gov/ Interpretive Summary: This laboratory focuses on characterization of small scale evolutionary events that correlate with the ability of Salmonella enterica to efficiently contaminate eggs and to cause an associated increase in human illness. Currently, Salmonella enterica serotype Enteritidis is the only one out of 2400 serotypes that efficiently contaminates the eggs of hens and that is linked to substantial human disease. There has been concern that other Salmonella serotypes are evolving the ability to contaminate eggs; thus, new tools are needed to screen for this type of evolution. Results from these genomic studies provide conclusive evidence that serotype Heidelberg has more small-scale genetic similarities with serotype Enteritidis than it does with Typhimurium, which is frequently associated with contamination of the chicken carcass. Sequences identified by this research can be used to improve detection and control of Salmonella serotypes that are in the process of evolving new characteristics that propagate food borne illness.
Technical Abstract: Two intergenic spacer regions (ISRs), which are defined as the 179bp between the end of the 23S rrlH ORF and the start of the 5S rrfH rDNA (ISR 1) and the 190bp between the end of the rrfH rDNA and start of the transfer RNA aspU ORF (ISR 2) of Salmonella enterica serotype Enteritidis, were sequenced from 64 isolates that included 6 different pathogenic Salmonella enterica serotypes, namely Typhimurium, Pullorum, Gallinarum, Heidelberg, Newport, and Enteritidis. D1 serotypes, namely Pullorum, Gallinarum, and Enteritidis grouped with serotype group B Typhimurium var Copenhagen, which is historically associated with colonization of pigeons. Other B serotypes, namely Typhimurium and Heidelberg, formed a second clade. Newport, a serotype C1 Salmonellae, formed a third clade that included similarity to the enteric fever disease serotypes Paratyphi A (serotype A) and Typhi (D1). Results for ISR 2 showed that Heidelberg, serotype B, shares more evolution with D1 serotypes that are associated with egg contamination than it does with typical B serotypes such as Typhimurium. ISR 2 sequence was also useful for differentiating between the avian adapted serotypes Salmonella Pullorum and Salmonella Gallinarum. In summary, these results suggest that the ISR sequences flanking 5S rDNA rrfH are useful for monitoring evolutionary trends within Salmonella enterica that correlate to avian adaptation and egg contamination.