DETERMINATION OF ESCHERICHIA-COLI SHIGA-L IKE TOXINS BY MEANS OF THE MTT-BIOASSAY

Tissue culture cells' metabolism and viability are measured by the mit ochondrial reduction rate of a yellow tetrazolium salt (MTT) to blue f ormazan crystalls in the MTT-bioassay. Thus the MTT-bioassay is a stan dardizable and reproducible bioassay for measuring cytotoxicity or cyt ostimulation. It is shown that the MTT-bioassay is also very suitable for determining bacterial cytotoxins using Escherichia coli's Shiga-li ke toxins as example. 177 strains of E.coli, isolated from carcasses a nd organs of cattle, are classified biochemically and tested for cytot oxin production by means of the MTT-bioassay. One of these strains is recognized as producer of Shiga-like toxin 2. 4 Enterohemolysin-produc ing strains of E.coli are cultivated from a feces sample of a diarrhoe ic nubian ibex and identified as Shiga-like toxin 1 producers by help of the MTT-bioassay.