Comparison of phenotype nutritional profiles and phosphate metabolism genes in four serovars of salmonella enterica from water sources

Authors: Gorski, Lisa; Aviles Noriega, Ashley

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2023
Publication Date: 8/18/2023
Citation: Gorski, L.A., Aviles Noriega, A. 2023. Comparison of phenotype nutritional profiles and phosphate metabolism genes in four serovars of salmonella enterica from water sources. Microorganisms. 11. Article 2109. https://doi.org/10.3390/microorganisms11082109.
DOI: https://doi.org/10.3390/microorganisms11082109

Interpretive Summary: One issue when conducting surveillance of foods for Salmonella contamination is the bias of standard enrichment media. Contaminated foods may contain several different sub-types (serovars) of Salmonella, and some will outgrow others in enrichment media. This is a problem especially when serovars less likely to cause human illness (such as Salmonella Kentucky and Salmonella Give) mask the presence of more problematic serovars such as Enteritidis and Typhimurium. We studied several strains of Salmonella serovars Enteritidis, Give, Kentucky, and Typhimurium, and measured growth kinetics in the commonly used enrichment medium Buffered Peptone Water (BPW). When grown individually strains of the various serovars demonstrated similar growth in BPW as well as another common growth medium, Trypticase Soy Broth. Nutritional characteristics of the serovars were compared by measuring utilization of 950 compounds, and some nutritional differences were noted between the serovars. Strains of Enteritidis and Typhimurium utilized sugars such as D-mannose and D-mannitol as carbon and energy sources better than strains of Kentucky. Strains of Kentucky utilized amino acids as sole carbon and energy sources better than the Enteritidis and Kentucky strains. Salmonella Kentucky strains showed better utilization of inorganic phosphate as the sole phosphorus source than the other strains. The sequences of nine genes involved in phosphate metabolism were compared, and there were differences between serovars in the catalytic – ATP binding domain of the histidine kinase phoR. Analysis of the predicted PhoR amino acid sequences from additional Salmonella genomes indicated a conservation of sequences each within the Typhimurium, Give and Enteritidis serovars. However, three different PhoR versions were observed in S. Kentucky.

Technical Abstract: The surveillance of foods for Salmonella is hindered by bias in common enrichment media where serovars implicated in human illness are outgrown by less virulent serovars. We examined four Salmonella serovars, two common in human illness (Enteritidis and Typhimurium) and two that often dominate enrichments (Give and Kentucky) for factors that might influence culture bias. The four serovars had similar growth kinetics in Tryptic Soy Broth and Buffered Peptone Water. Phenotypic microarray analysis with 950 chemical substrates to assess nutrient utilization and stress resistance revealed phenotype differences between serovars. Strains of S. Enteritidis had better utilization of plant-derived sugars such as xylose, mannitol, rhamnose, and fructose, while S. Typhimurium strains were able to metabolize tagatose. Strains of S. Kentucky used more compounds as phosphorus sources and grew better with inorganic phosphate as the sole phosphorus source. The sequences of nine genes involved in phosphate metabolism were compared, and there were differences between serovars in the catalytic – ATP binding domain of the histidine kinase phoR. Analysis of the predicted PhoR amino acid sequences from additional Salmonella genomes indicated a conservation of sequences each within the Typhimurium, Give and Enteritidis serovars. However, three different PhoR versions were observed in S. Kentucky.