Is Escherichia coli invading tubuloepithelial cells?

Area of Science:

• Microbiology
• Pathogenesis
• Cell Biology

Background:

• Urinary tract infections (UTIs) initiate with Escherichia coli adhesion to host epithelium.
• Bacterial surface factors like fimbriae, adhesins, K antigen, and hemolysin modulate UTI pathogenesis.
• Understanding these interactions is crucial for developing targeted UTI prevention and treatment strategies.

Purpose of the Study:

• To investigate the role of K5 antigen and hemolysin expression in Escherichia coli adherence and internalization into host epithelial cells.
• To elucidate the contribution of bacterial surface factors to the initial stages of UTI development.

Main Methods:

• Utilized isogenic E. coli O18 strains with varying K5 antigen and hemolysin expression.
• Employed a permanent porcine tubuloepithelial cell line (LLC-PK1) for in vitro adhesion and internalization assays.
• Quantified bacterial adherence and internalization rates for each strain.

Main Results:

• E. coli strains expressing K5 antigen exhibited significantly reduced adherence and internalization compared to K-negative strains.
• Hemolysin expression by E. coli strains led to a notable increase in both adherence and internalization.
• Bacterial internalization was strongly correlated with initial adherence levels.

Conclusions:

• K5 antigen acts as a negative regulator of E. coli adhesion and internalization, potentially hindering UTI initiation.
• Hemolysin expression promotes E. coli attachment and subsequent entry into host epithelial cells, facilitating infection.
• Bacterial internalization into host cells is primarily a consequence of adherence, resembling an endocytic process rather than active invasion.