Methods for checking up screening tests for detection of shigatoxin-producing Escherichia coli by using PCR

Methods for making check ups of STEC-Screening-PCRs by using internal and e xternal systems are given. A control-DNA with identical primer binding site s in relation to the target-DNA (stx-genes) was produced and by HPLC-chroma tography quantified. It was used in an internal system. But we had to use t oo high concentrations of this DNA for making the check up in each sample. A false negative result could be shown in samples with a low sa content as a result of this coamplification process. Therefore we used an external sys tem. A control-DNA with heterologous primer binding sites in relation to th e stx-screening-PCR and the special primers were given in each vessel. The optimized system was used for making investigations of some faecal samples from cattle.