Doores et al  demonstrated that normal healthy mushrooms have high bacterial populations. Total bacterial numbers ranged from 6.3 to 7.2 log CFU/g of fresh mushroom tissue. The majority (54.0%) of bacteria isolated from the mushrooms were identified as fluorescent pseudomonads with flavobacteria comprising the second largest group (10.0%). Recent experiments in our laboratory have confirmed this pattern, but we have also been able to isolate the chryseobacterium genus (5.5 log CFU/g) and the coryneform bacterial genus (5.6 log CFU/g) from freshly harvested mushrooms. Halami et al.  isolated lactic acid bacteria belonging to the Lactobacillus sp. and Pediococcus sp. from fresh mushrooms by incubating agaricus mushrooms in deMan Rogosa and Sharpe (MRS) broth for enrichment of resident lactic acid bacteria. However, the bacterial counts were not enumerated in their study.
Mushrooms also contain significant levels of yeasts and molds. Studies in our laboratory have shown that freshly harvested mushrooms harbor approximately 3 log CFU of molds and 6 log CFU of native yeast per gram of fresh tissue (Figure 6.2).
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