Adhesion and internalization of E. coli strains expressing various pathogenicity determinants

Area of Science:

• Microbiology
• Pathogenesis
• Cell Biology

Background:

• Urinary tract infections (UTIs) begin with bacterial adhesion to epithelial cells.
• Pathogen surface factors like fimbriae, K antigen, and hemolysin influence bacterial adherence and internalization.
• Understanding these interactions is crucial for developing strategies against recurrent UTIs.

Purpose of the Study:

• To investigate the role of specific Escherichia coli surface antigens (K5 antigen, hemolysin) in bacterial adherence and internalization into host epithelial cells.
• To determine the mechanism of bacterial internalization, specifically whether it is endocytosis or invasion.
• To assess the impact of cytoskeletal inhibitors on bacterial internalization.

Main Methods:

• Utilized a permanent line of porcine tubuloepithelial cells (LLC-PK1).
• Compared adherence and internalization of various E. coli O18:K5 mutants with differing antigen expression.
• Administered cytoskeletal inhibitors (cytochalasin B, cytochalasin D, colchicine, chloroquine) to assess their effect on bacterial internalization.

Main Results:

• Strains expressing K5 antigen showed reduced adherence and internalization compared to K-negative strains.
• Hemolysin expression increased bacterial adherence and internalization.
• Cytoskeletal inhibitors significantly inhibited bacterial internalization, supporting an endocytic mechanism.

Conclusions:

• Bacterial internalization by tubuloepithelial cells appears to be a form of receptor-mediated endocytosis rather than active bacterial invasion.
• The presence of K5 antigen may hinder bacterial entry, while hemolysin facilitates it.
• This endocytic pathway is potentially significant in the pathogenesis of recurrent urinary tract infections.