Adherence to and cytotoxicity of Escherichia coli for eucaryotic cell lines quantified by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide).

Adherence of Escherichia coli to human epithelial cells (HEp-2) was studied using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) which is cleaved by enzymes of eucaryotic or procaryotic cells to formazan. This method allows to quantify adherence of Escherichia coli to HEp-2 cells and offers the advantage of assaying a large number of eucaryotic cells without using specific antisera or radioactive material. Furthermore, toxic effects of isolated hemolysin cloned in Escherichia coli onto a renal tubular cell line (LLC-PK1) was investigated by this method, showing reduced cellular viability of tubular cells after an incubation period of 10 to 20 min. MTT is therefore considered to be useful to assay the adherence of Escherichia coli to eucaryotic cells and to quantify toxic effects in eucaryotic cells induced by bacterial virulence factors.