Antibacterial Activity of Cultivated and Wild Basidiomycetes

The emergence of antibiotic-resistant bacteria has made the search for new antibiotics imperative. Basidiomycetes have not been screened for antibiotics, largely because most basidiomycetes are difficult to cultivate. Auricularia spp. and Lyophyllum shimeji are edible basidiomycetes that are often used in Asian cooking. Lepiota sp. and Chroogomphus sp. grow wild on the west coast of the United States. Aqueous, methanolic, ethanolic and ethyl acetate extracts of these mushrooms were prepared (500 mg/mL) and examined for antibacterial activity against gram-negative (Esherichia coli and Pseudomonas aeruginosa) and gram-positive (Staphylococcus aureus) bacteria using agar-diffusion assays. Ethyl acetate extracts of A. auricula-judae inhibited P. aeruginosa and S. aureus, including methicillin-resistant S. aureus. The minimal bacteriostatic concentrations against P. aeruginosa and S. aureus and mechanisms of action are currently being determined. Our results demonstrate that A. auricula-judae may be a good source of an antimicrobial drug or food preservative. Further studies are required to determine the effect of these extracts on other bacteria and identify the compound(s) that are responsible for the antibacterial effects.