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Title: PATHOTYPING OF SALMONELLA ENTERICA BY ANALYSIS OF SNPS IN CYAA AND FLANKING 23S RIBOSOMAL SEQUENCES

Author
item MORALES, CESAR - UGA
item Musgrove, Michael
item HUMPHREY, T. - UNIVERISTY OF BRISTOL, UK
item Cates, Carolyn
item Gast, Richard
item Guard, Jean

Submitted to: Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2006
Publication Date: 4/1/2007
Citation: Bouldin, J.G., Musgrove, M.T., Humphrey, T.J., Cates, C.W., Gast, R.K., Morales, C. 2007. Pathotyping of Salmonella enterica by analysis of SNPs in cyaA and flanking 23S ribosomal sequences. Environmental Microbiology.9:1047-1059.

Interpretive Summary: The egg-contaminating phenotype of Salmonella enterica serotype Enteritidis was linked to single-nucleotide polymorphisms (SNPs) occurring in cyaA, which encodes adenylate cyclase that produces cAMP and pyrophosphate from ATP. Ribotyping indicated that SNPs in cyaA were linked to polymorphisms occurring in the rrlC and rrlA 23S ribosomal subunits. Phylogenetic analysis of cyaA discriminated between Salmonella enterica serotypes and within serotype Enteritidis. Serotypes Typhimurium, Heidelberg, and Enteritidis produced one, three, and six cyaA allelic variants, respectively, among the set of 56 isolates examined. Asparagine702 of CyaA was converted to serine in a biofilm-producing isolate. Statistical analysis was applied to 42 other genes encoding proteins between 800 and 1000 amino acids (aa). Results show that the 848-aa CyaA of serovar Enteritidis evolved by nucleotide substitutions that did not significantly alter the purine-to-pyrimidine nucleotide substitution ratio, which was a characteristic of large genes that was positively correlated with increasing gene size. In summary, these analyses link SNPs occurring in the rrlC-rrlA genomic fragment of S. enterica to genetic drift within S. Enteritidis that is associated with egg contamination.

Technical Abstract: The egg-contaminating phenotype of Salmonella enterica serotype Enteritidis was linked to single-nucleotide polymorphisms (SNPs) occurring in cyaA, which encodes adenylate cyclase that produces cAMP and pyrophosphate from ATP. Ribotyping indicated that SNPs in cyaA were linked to polymorphisms occurring in the rrlC and rrlA 23S ribosomal subunits. Phylogenetic analysis of cyaA discriminated between Salmonella enterica serotypes and within serotype Enteritidis. Serotypes Typhimurium, Heidelberg, and Enteritidis produced one, three, and six cyaA allelic variants, respectively, among the set of 56 isolates examined. Asparagine702 of CyaA was converted to serine in a biofilm-producing isolate. Statistical analysis was applied to 42 other genes encoding proteins between 800 and 1000 amino acids (aa). Results show that the 848-aa CyaA of serovar Enteritidis evolved by nucleotide substitutions that did not significantly alter the purine-to-pyrimidine nucleotide substitution ratio, which was a characteristic of large genes that was positively correlated with increasing gene size. In summary, these analyses link SNPs occurring in the rrlC-rrlA genomic fragment of S. enterica to genetic drift within S. Enteritidis that is associated with egg contamination.