Cloned genes of the aerobactin system of virulent avian Escherichia coli do not confer virulence to recombinant strains

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• Septicemic avian Escherichia coli strains possess virulence factors contributing to disease.
• Iron uptake systems, such as aerobactin, are often implicated in bacterial virulence.

Purpose of the Study:

• To investigate the role of the aerobactin iron uptake system as a virulence determinant in avian E. coli.
• To assess if the aerobactin system alone confers pathogenicity in chickens.

Main Methods:

• Cloning of the aerobactin region and its receptor gene from a virulent avian E. coli plasmid (pMV14).
• Construction of a recombinant plasmid (pGMV1) containing the aerobactin system.
• Immunological cross-reactivity assessment of the aerobactin receptor protein.
• Virulence assays in chickens using E. coli strains with and without the cloned aerobactin system.

Main Results:

• The physical map of the cloned aerobactin region was similar to known aerobactin systems.
• The cloned aerobactin receptor protein showed immunological similarity to known receptors.
• Avirulent E. coli strains harboring the recombinant plasmid (pGMV1) remained avirulent in chickens.
• Only the wild-type strain with the aerobactin system exhibited virulence.

Conclusions:

• The aerobactin iron uptake system, in isolation, does not confer virulence in avian E. coli.
• Other virulence factors are essential for the pathogenicity of avian E. coli strains.