Objective    To establish a semi-quantitative method to analyze the attaching and effacing (A/E) lesions on host cells caused by pathogenic

Escherichia coli

(

E. coli

).     Methods    HeLa cells were infected with enteropathogenic or enterohemorrhagic

E. coli

strains (EPEC 43095

EHEC O157∶H7 Sakai

EHEC O157∶H7 00B015 and

E. coli

DH5α) and visualized by Giemsa staining and fluorescence actin staining (FAS). Then the numbers of microcolonies and actin polymerizations formed on the cells were counted and calculated.     Results    All

EPEC induced stronger A/E lesions than EHEC on HeLa cells (

P

<

0.05). The EPEC 43095 caused the strongest A/E lesions among these

E. coli

strains detected. Although the ability of EHEC Sakai to attach to HeLa cells was similar to that of EHEC 00B015 (P>0.05)

EHEC Sakai induced stronger actin polymerizations in host cells than EHEC 00B015 (

P

<

0.05).     Conclusion    A semi-quantitative method to analyze the A/E lesions of host cells caused by pathogenic

E. coli

is successfully established. This work contributes to further studies on pathogenicity of the pathogenic

E.coli

.