Detection and Molecular Identification of Plasmid Virulence Genes in Salmonella enterica serovar typhimurium Isolated from Human and Animals by Multiplex PCR Method

Abstract

Background: Salmonella enterica is a zoonotic species that can acquire its resistance in livestock. In humans, Salmonella typhimurium is a major etiological agent of food-borne salmonellosis. The identification of Salmonella spp. by traditional cultural techniques requires 4 to 5 days. The polymerase chain reaction (PCR) offers a simple tool for the rapid detection of Salmonella. Methods: Fifty-five S. typhimurium isolates from bovine, poultry and human sources were isolated and analyzed with biochemical and serological tests. Firstly, multiplex PCR assay with four sets of primers was selected for invA, rfbj, fliC and fljB genes. In the second stage, a simple PCR method with one set primer was applied to detect spvA and spvB genes. Also, multiplex PCR assay with two set primers was carried out to simultaneously detect and identify invA and spvC genes in S. typhimurium. Results: Analysis of the samples showed that while the presence of spvA, spvB and spvC genes in S. typhimurium from the bovine source was 100% (15/15), these same genes were present in 65% (13/20) of the poultry sources. The study also showed that spvA, spvB and spvC genes were present in 85% of human source. Conclusion: This study showed that M- PCR of invA, rfbJ, fljB, and fliC genes were fast, simple, less expensive, accurate and specific in identification S. typhimurium. The advantage of multiplex PCR was that it could simultaneously identify the Salmonella strains which had a virulence plasmid thus facilitating the search for specific etiologic Salmonella serovars. The higher prevalence of spv genes among bovine sources can be injurious for public health.

Keywords

• Multiplex PCR
• Salmonella typhimurium
• Virulence genes.