Detection of virulence genes and investigation of the immunogenicity of outer membrane proteins of salmonella enterica

Abstract

Salmonella enterica is one of the most important food-borne pathogens, causing a variety of diseases in humans and animals. This study aimed to detect the virulence genes in 33 S. enterica strains isolated from patients and to investigate the immunogenicity of the outer membrane proteins (OMPs) of S. enterica serovar Typhimurium. The aggregative fimbriae (agfA) gene was detected in all S. enterica isolates except one strain, Salmonella Paratyphi C strain SA7. In addition, 81.8% of the isolates harbored the sefC gene (fimbrial protein). However, all of the tested S. enterica isolates possessed the fimA, hilA, invA, stn, and misL virulence genes, regardless of serovar. The predominant OMPs of S. enterica Typhimurium SA3 identified by 12% sodium dodecyl sulfate-Polyacrylamide Gel Electrophoresis (PAGE) were used as eliciting antigens in the experimental mice. The results of the protection studies indicated that the selected OMPs conferred varying degrees of protection. However, the highest protection was observed using the 38-kDa OMP, which provided 100% protection to mice challenged with 50× LD50 of Salmonella Typhimurium SA3 and 75% protection to mice subjected to an even higher bacterial challenge of 100× LD50 . The humoral response in mice caused by the 38-kDa OMP was confirmed using an immunodiffusion assay. This 38-kDa OMP is a promising candidate for the vaccine development against S. enterica Typhimurium. Further research on the protein structure was recommended.