Results
Table 1 shows the locations where the mushroom samples were
purchased in China. The amounts of samples obtained are also
indicated and in some locations, two samples from different
retail units were purchased. Forty-eight samples, consisting of 27
Shiitake (L. edodes) and 21 Wood Ear mushrooms (A. auricular)
from different regions of China were analyzed for spores of both
proteolytic C. botulinum and non-proteolytic C. botulinum. Some
samples from the same city were pooled. For the detection test,
all samples were negative for the presence of spores of proteolytic
C. botulinum and non-proteolytic C. botulinum (data not shown).
Tables 2 and 3 show the results of the LOD experiment using samples
of dried L. edodes and A. auricular. Firstly (Table 2), an equal
weight, 5 g, of L. edodes and A. auricula collected from China was
added together for determining the LOD protocol (there was
insufficient mushroom material remaining to test each individually).
The results presented in Table 2 show that these mushroom
enrichments supported growth of both groups of C. botulinum even
though the detection test yielded only negative samples. It should
be noted that a positive PCR result requires one or more spores to
germinate, and for the emerged cells to multiply in the enrichment
culture/subculture to a concentration that exceeds the detection
limit of the PCR test (Lindström et al., 2001). As it was not possible
to source further samples directly from China, similar dried mushrooms
of L. edodes and A. auricular, which were labeled as originating
from China, were purchased from a retail outlet in Norwich, United
Kingdom.