3.2. Analysis of non-fecal preparations by direct PCR (standard protocol)
The feasibility of the APHA1 primers for direct amplification of A. phalloides traces in mixed mushroom (raw, fried and digested) preparations was investigated by a series of experiments. Mixed mushroom samples (~ 1 g total mass) were supplied with 2 ml ATL lysis buffer and homogenized (see Materials and methods). Aliquots from homogenized samples were diluted (1:100, 1:1,000 and
1:10,000) with water. Five-microlitre aliquots of diluted samples were used as template for direct PCR. PCR products of the expected size could be generated with all raw (Fig. 6 of ESM-2) and fried (Fig. 7 of ESM-2) mushroom preparations. In addition, target amplification by direct PCR was observed with diluted artificial gastric content (i.e. a homogenate composed of fried and digested
A. phalloides mixed with an excess of A. bisporus) (Fig. 8 of ESM-2).
3.3. Analysis of vomit and fecal specimens by direct PCR (modified protocol)
In order to enable rapid detection of mushroom traces in stool samples, a short protocol for feces pre-processing (including steps of water-ether sedimentation and cell disruption by bead beating, see 2.4.) was established. Furthermore, our standard recipe for direct PCR (see 2.7.1.) was modified by adding BSA (0.6% wt/vol) and by increasing the reaction volume (from 20 µl to 50 µl). With the use of this combined novel approach, we were able to discover highly diluted A. phalloides traces in spiked stool specimens (Fig. 10 of ESM-2). Notably, results obtained by the direct PCR approach were comparable with the results obtained by PCR using purified DNA from the same samples (data not shown). The modified direct PCR approach was applied to investigate samples (vomit, stool) from clinical cases of suspected mushroom poisoning. Fragments of the expected size were amplified and documented on agarose gel (see Figs. 9 and 11 of ESM-2). PCR products were purified and sequenced. Sequence data were subjected to BLAST analysis and affiliated with rDNA from A. phalloides (a reference sequence can be found in ESM-2).