ARS | Publication request: Detection of Real-Time Evolution in Salmonella Recovered from the on-Farm Poultry Environment

Submitted to: Advances in Pre-harvest Reduction of Salmonella and Poultry
Publication Type: Abstract
Publication Acceptance Date: August 25, 2005
Publication Date: August 25, 2005
Citation: Bouldin, J.G., Morales, C., Cates, C.W. 2005. Detection of real-time evolution in salmonella recovered from the on-farm poultry environment. Meeting Abstract. FSIS meeting, Athens, GA, August 25, 2005.

Technical Abstract: Correlation of the egg-contaminating phenotype of Salmonella enterica serotype Enteritidis was made to single nucleotide polymorphisms (SNPs) occurring in cyaA, which encodes adenylate cyclase that produces cAMP and pyrophosphate from ATP. Ribotyping also indicated that SNPs in cyaA were co-inherited with polymorphisms occurring in rrlC and rrlA 23S ribosomal sequences after primers were included in analysis that established rDNA identity in gels. Phylogenetic analysis of cyaA discriminated between serotypes and between serotype Enteritidis phage- and pathotypes, which are clonally related subpopulations that vary in their ability to contaminate eggs. Serotypes Typhimurium, Heidelberg, and Enteritidis produced one, three and six cyaA allelic variants, respectively, amongst a set of 56 isolates examined. Rep-PCR obscured the correlation of genotype to phenotype, because it identified every isolate tested as an individual. Asparagine702 of CyaA was converted to serine in a biofilm-producing strain, which was significantly deficient in its ability to grow on non-catabolite carbohydrate sources. Statistical analysis of 42 other genes that encoded proteins between 800 to 1000 amino acids revealed that the 848aa CyaA of serovar Enteritidis evolved by nucleotide substitutions that did not significantly alter the purine to pyrimidine nucleotide substitution ratio and that did not correlate with increasing gene size. These analyses strongly suggest that the rrlC-rrlA genomic fragment of Salmonella enterica harbors SNPs that are markers for genetic drift within S. Enteritidis that are linked to egg contamination and to metabolism. These data support the concept that evolution of outbreak potential by the Salmonellae can be monitored in real-time with high throughput technology.