Location: Meat Safety & Quality ResearchTitle: Genome sequence of the thermotolerant foodborne pathogen Salmonella enterica serovar Senftenberg ATCC 43845 and phylogenetic analysis of Loci encoding increased protein quality control mechanisms
Submitted to: mSystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2017
Publication Date: 2/28/2017
Citation: Nguyen, S.V., Harhay, G.P., Bono, J.L., Smith, T.P., Harhay, D.M. 2017. Genome sequence of the thermotolerant foodborne pathogen Salmonella enterica serovar Senftenberg ATCC 43845 and phylogenetic analysis of Loci encoding increased protein quality control mechanisms. mSystems. 2:e00190-16. https://doi.org/10.1128/mSystems.00190-16.
Interpretive Summary: Thermal interventions are commonly used by the food industry to control for bacterial contaminants. The emergence of heat resistant bacteria within beef patties grilled to well done has been a cause for concern recently. Genomic sequencing has revealed the presence of a conserved gene sequence that confers heat resistance and appears to have been horizontally transferred between members of some bacteria. A historical isolate of Salmonella originally characterized by ARS in 1968, has been used in numerous heat resistance studies by food microbiologists over the last several decades. The genetic determinants of this isolate’s unusually high heat resistance have not been previously characterized. Whole genome sequencing of the Salmonella isolate revealed the presence of not one but two gene clusters strongly related to gene clusters previously identified in other heat resistant foodborne pathogens. This discovery marks the first report of the presence of these two gene clusters in the important pathogen Salmonella and offers clues to the unusually high heat resistance of this strain. Finally, the presence of the two gene clusters on a horizontally transmissible genetic element underscores the potential for transfer of this heat resistance phenotype to other foodborne pathogens.
Technical Abstract: Salmonella enterica subsp. enterica bacteria are important foodborne pathogens with major economic impact. Some isolates exhibit increased heat tolerance, a concern for food safety. Analysis of a finished-quality genome sequence of an isolate commonly used in heat resistance studies, S. enterica subsp. enterica serovar Senftenberg 775W (ATCC 43845), demonstrated an interesting observation that this strain contains not just one, but two horizontally acquired thermotolerance locus homologs. These two loci reside on a large 341.3-kbp plasmid that is similar to the well-studied IncHI2 R478 plasmid but lacks any antibiotic resistance genes found on R478 or other IncHI2 plasmids. As this historical Salmonella isolate has been in use since 1941, comparative analysis of the plasmid and of the thermotolerance loci contained on the plasmid will provide insight into the evolution of heat resistance loci as well as acquisition of resistance determinants in IncHI2 plasmids