Plasmid-mediated adhesion in enteropathogenic Escherichia coli

Area of Science:

• Microbiology
• Molecular Biology
• Infectious Diseases

Background:

• Enteropathogenic Escherichia coli (EPEC) are a significant cause of diarrheal disease.
• Plasmid profiles and adherence capabilities are key characteristics of pathogenic bacteria.
• HEp-2 cell adherence is a common in vitro model for studying bacterial pathogenicity.

Purpose of the Study:

• To investigate the role of plasmids in the adherence of classical serotype enteropathogenic Escherichia coli to HEp-2 cells.
• To identify specific plasmids associated with HEp-2 cell adherence and in vivo intestinal adhesion.

Main Methods:

• Survey of plasmid profiles in 32 enteropathogenic Escherichia coli strains.
• Assessment of HEp-2 cell adherence for each strain.
• Genetic manipulation of a specific 55 Md plasmid (pMAR2) in strain E2348, including transposon marking for ampicillin resistance.
• Plasmid curing experiments to assess the effect on HEp-2 adherence.
• Plasmid transfer experiments to a non-adherent E. coli K12 strain (HB101).
• In vivo adhesion studies using a colostrum-deprived piglet model.

Main Results:

• Thirty-one of 32 EPEC strains harbored a 50-70 Md plasmid, with many showing HEp-2 adherence.
• Strain E2348 (O127:H6), a diarrhea-causing EPEC, possesses a 55 Md plasmid (pMAR2) crucial for HEp-2 adherence.
• Curing E2348 of pMAR2 abolished HEp-2 adherence; HB101 gained HEp-2 adhesiveness upon receiving this plasmid.
• Plasmid presence correlated with in vivo intestinal adhesion in piglets.

Conclusions:

• A specific 55 Md plasmid (pMAR2) is essential for the HEp-2 cell adherence of enteropathogenic Escherichia coli strain E2348.
• This plasmid confers both in vitro (HEp-2 cells) and in vivo (intestinal) adhesive properties.
• Plasmid-mediated adherence is a critical factor in the pathogenicity of enteropathogenic Escherichia coli.