Salmonella Abortusequi strains of equine origin harbor a 95kb plasmid responsible for virulence in mice.

The research article investigates how a particular plasmid found in Salmonella Abortusequi strains contributes to the virulence of this bacterial species in mice.

Overview and Background

• The study is centred on Salmonella Abortusequi strains, a type of bacteria. These strains are generally found in horses (equine origin).
• The researchers have focussed on a large circular DNA molecule or plasmid (known as pSA95), which is 95 kilobases (kb) in size that most of these S. Abortusequi strains harbor.

Research Methodology

• To assess the presence and role of pSA95 in conferring virulence, the team utilized PCR (Polymerase Chain Reaction) and Southern blot techniques. These are molecular biology methods used for DNA detection and analysis.
• They genetically manipulated a strain of S. Abortusequi to remove the plasmid (creating a pSA95-cured strain), which was then tested on mice to examine the difference in virulence.

Key Findings

• The team discovered that the pSA95-cured strain was notably less harmful to mice, being 48 times less virulent than its original, plasmid-harbouring parent strain.
• This significant drop in virulence indicates that the plasmid pSA95 plays a pertinent role in the virulence of S. Abortusequi.
• To further verify this observation, they restored the pSA95 plasmid back into the cured strain and found that the virulence was reinstated, thereby confirming the plasmid’s role in affecting virulence.

Conclusion and Implications

• The study provides clear evidence that pSA95 confers virulence on S. Abortusequi in an animal model (mice), suggesting a potential target for developing treatments or preventive measures against infections caused by this bacterium.
• This research marks the first report describing a virulence plasmid of S. Abortusequi, making it a significant contribution to our understanding of Salmonella species’ pathogenesis and potentially paving the way for further investigation into this relatively unexplored area.