To define the minimal cell count that was detectable by this multiplex PCR system, different numbers of bacterial cells from pure cultures were adjusted in sterile filtered wine. Furthermore, pasteurised musts were spiked by different LAB species varying in cell count. Cell concentrations were checked by counting cells in a counting chamber, as well as by plating on MRS agar. One ml of must or wine containing 108–100 cells/ml was used for DNA extraction, which was performed as described in section 2.3. In some cases a further purification step was carried out: the eluted DNA was precipitated and washed a second time to remove potential PCR inhibitors. To increase the DNA concentration the amount of the elution buffer was reduced to 60 μl. For multiplex PCR 5 μl template DNA was used.