Use of mixed infections with Salmonella strains to study virulence genes and their interactions in vivo

Area of Science:

• Microbiology
• Infectious Diseases
• Bacterial Pathogenesis

Background:

• The Salmonella-mouse model is used for systemic infection studies.
• High-dose inoculation leads to broad cell multiplication, not just clonal amplification.
• This allows for in vivo screening of bacterial strains within a single host.

Purpose of the Study:

• To develop and utilize methods for screening bacterial virulence and gene expression in vivo.
• To investigate virulence gene interactions using mixed infections.
• To refine the competitive index assay for studying bacterial pathogenesis.

Main Methods:

• Employing a Salmonella-mouse model of systemic infection.
• Utilizing high-dose inoculation to ensure multiplication of multiple inoculum cells.
• Conducting mixed infections with mutant and wild-type bacterial strains.
• Applying a variation of the competitive index method with single and double mutants.

Main Results:

• Demonstrated that high-dose inoculation supports the multiplication of numerous cells from the initial inoculum.
• Established mixed infection models for sensitive assessment of virulence attenuation (competitive index).
• Successfully applied a modified mixed infection approach to study in vivo interactions between bacterial virulence genes.

Conclusions:

• The Salmonella-mouse model with high-dose inoculation is effective for in vivo screening of bacterial strains.
• Mixed infection strategies, including competitive index assays, are valuable for studying bacterial virulence and gene function.
• This methodology facilitates the investigation of complex virulence gene interactions within a host environment.