DefinePK

Research Objective

To investigate the phylogenetic relationships of potato-borne Salmonella enterica with clinical lineages and to assess the prevalence and genetic diversity of S. enterica in imported and local potato seed tubers.

Methodology

The study involved the collection of potato seed tubers from local and imported varieties. Salmonella enterica was isolated using pre-enrichment and selective plating on bismuth sulfite agar. Identification was confirmed using biochemical and serological tests. Molecular identification involved PCR amplification of the invA gene. Phylogenetic analysis was conducted using Random Amplified Polymorphic DNA (RAPD) PCR and sequencing of the invA gene, followed by cluster analysis using UPGMA and Pearson correlation methods.

Methodology Flowchart

                        graph TD
    A[Sample Collection: Potato Seed Tubers] --> B[Isolation of Salmonella species];
    B --> C[Biochemical & Serological Tests];
    C --> D[Molecular Identification: invA Gene PCR];
    D --> E[RAPD-PCR for Strain Differentiation];
    D --> F[invA Gene Sequencing];
    E --> G[Cluster AnalysisRAPD];
    F --> H[Cluster AnalysisinvA];
    G --> I[Phylogenetic Analysis];
    H --> I;
    I --> J[Interpretation & Conclusion];                    

Discussion

The study highlights the prevalence of S. enterica in both local and imported potato seed tubers, emphasizing their role as a potential reservoir for human pathogens. The invA gene, a virulence factor, was found in a high percentage of isolates and showed genetic heterogeneity, useful for lineage characterization. RAPD-PCR and invA gene sequencing combined with phylogenetic analysis proved effective in differentiating environmental and clinical Salmonella strains.

Key Findings

Out of 67 S. enterica isolates recovered from potato seed tubers, 63 (94.02%) carried the invA gene. RAPD analysis grouped the isolates into three distinct clusters. Salmonella strains 7S-Moz-L and 1S-Kar-I showed genetic similarity to the clinical strain S. typhi 5S-CL2. Phylogenetic analysis of invA sequences revealed homology between Salmonella strain 9SF-Ast-L and S. typhi 5S-CL2, and an evolutionary relationship between Salmonella strain 1S-Kar-I and local strains 7S-Moz-L and 8S-Qas-L.

Conclusion

Pre- and post-harvest surveillance strategies using molecular methods like RAPD-PCR and invA gene sequencing are crucial for rapid identification and characterization of Salmonella strains in potato seed tubers. This can help prevent the transfer of pathogens to humans, restrict unsafe imports and exports, and improve food safety standards.

Fact Check

1. 94.02% of isolates carried the invA gene: The study states that 63 out of 67 S. enterica isolates confirmed to carry the invA gene, which is approximately 94.02%. This is confirmed in the text.
2. 67 S. enterica isolates recovered: The study reports recovering a total of 67 Salmonella isolates from potato seed tubers. This is confirmed in the text.
3. Approximately 93.8 million foodborne illnesses and 155,000 deaths annually due to Salmonella: This statistic is cited from Heredia and García (2018) in the introduction.

Mind Map