adherence patterns of diarrheagenic escherichia coli strains isolated from children with gastrointestinal diarrhea and matched controls in a hep-2 cell adhesion assay

Escherichia coli is considered as the main cause of epidemic outbreaks and endemic cases of child diarrhea. in the present study, the capacity of a large collection of escherichia coli (e. coli) strains and matched controls was investigated to determine their adherence pattern on hep-2 cell lines. a total of 66 pure e. coli strains, which were previously isolated from children aged less than 12 years with diarrhea, were selected for adherence assay. moreover, 2 e. coli strains, with known adherence patterns, obtained from the persian type culture collection were used as the control. hep-2 cell monolayers (50 to 70% confluence) were grown on glass cover slips. subsequently, 20 μl of bacterial cultures (2 × 10^6 cfu/ml bacteria) was added into each well, and the plates were incubated in a humid atmosphere with 5% co2 for 3 hours. then, culture medium was aspirated from the monolayers, which were washed 4 times with phosphate-buffered saline, fixed in 70% aqueous methanol for 5 minutes, stained with giemsa stain, and examined using light microscopy. in total, 66 e. coli strains were evaluated for their adherence pattern on hep-2 cell line. all the isolates adhered to the hep-2 cells with the exception of 3. the other 63 showed aggregative adherence (aa) (34%), localized adherence (la) (31%), or diffuse adherence (da) (29%) patterns. the present investigation revealed that this assay is convenient and economical for identification of a large number of diarrheagenic e. coli isolates’ adherence to hep-2 cell lines.