Journal Article

Comparative genomic analysis and characterization of incompatibility group FIB plasmid encoded virulence factors of Salmonella enterica isolated from food sources

Khajanchi, Bijay K., Hasan, Nur A., Choi, Seon Young, Han, Jing, Foley, Steven L., Colwell, Rita R., Cerniglia, Carl E., Zhao, Shaohua

2017

Overview

Background The degree to which the chromosomal mediated iron acquisition system contributes to virulence of many bacterial pathogens is well defined. However, the functional roles of plasmid encoded iron acquisition systems, specifically Sit and aerobactin, have yet to be determined for Salmonella spp. In a recent study, Salmonella enterica strains isolated from different food sources were sequenced on the Illumina MiSeq platform and found to harbor the incompatibility group (Inc) FIB plasmid. In this study, we examined sequence diversity and the contribution of factors encoded on the IncFIB plasmid to the virulence of S . enterica . Results Whole genome sequences of seven S . enterica isolates were compared to genomes of serovars of S . enterica isolated from food, animal, and human sources. SeqSero analysis predicted that six strains were serovar Typhimurium and one was Heidelberg. Among the S. Typhimurium strains, single nucleotide polymorphism (SNP)-based phylogenetic analyses revealed that five of the isolates clustered as a single monophyletic S . Typhimurium subclade, while one of the other strains branched with S . Typhimurium from a bovine source. DNA sequence based phylogenetic diversity analyses showed that the IncFIB plasmid-encoded Sit and aerobactin iron acquisition systems are conserved among bacterial species including S. enterica . The IncFIB plasmid was transferred to an IncFIB plasmid deficient strain of S . enterica by conjugation. The transconjugant SE819::IncFIB persisted in human intestinal epithelial (Caco-2) cells at a higher rate than the recipient SE819. Genes of the Sit and aerobactin operons in the IncFIB plasmid were differentially expressed in iron-rich and iron-depleted growth media. Conclusions Minimal sequence diversity was detected in the Sit and aerobactin operons in the IncFIB plasmids present among different bacterial species, including foodborne Salmonella strains. IncFIB plasmid encoded factors play a role during infection under low-iron conditions in host cells.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Aerobactin / Analysis / Animal Genetics and Genomics / Bacteria / Bacterial Proteins - genetics / Biodiversity / Biomedical and Life Sciences / Caco-2 Cells / Comparative analysis / Conjugation / Deoxyribonucleic acid / DNA / E coli / Experiments / Food / Food Microbiology / Food sources / Gene sequencing / Genes / Genetic aspects / Genetic testing / Genomes / Genomic analysis / Genomics / Growth media / Health aspects / Human intestinal epithelial (Caco-2) cells / Humans / Incompatibility / Incompatibility group FIB plasmid / Infections / Intestine / Iron / Iron - metabolism / Iron acquisition systems (SitABCD and aerobactin) / Kinetics / Life Sciences / Metabolism / Metabolites / Microarrays / Microbial Genetics and Genomics / Microorganisms / Nucleotide sequence / Nucleotides / Operons / Pathogens / Phylogenetics / Phylogeny / Plant Genetics and Genomics / Plasmids / Plasmids - genetics / Polymorphism / Poultry / Prokaryote microbial genomics / Proteomics / Research Article / Roles / Salmonella / Salmonella enterica / Salmonella enterica - genetics / Salmonella enterica - isolation & purification / Salmonella enterica - metabolism / Salmonella enterica - physiology / Single nucleotide polymorphism (SNP) / Single nucleotide polymorphisms / Single-nucleotide polymorphism / Strains (organisms) / Virulence / Virulence (Microbiology) / Virulence factors / Virulence Factors - genetics