# Antimicrobial Efficacy of Edible Mushroom Extracts: Assessment of Fungal Resistance
## 1 Introduction  
The identification of foodborne pathogens or contaminants (fungi, bacteria) with increased resistance to conventional food-preservation methods or disinfectants is a recurring food safety and security concern. Studies have shown that invasive microbial infection including pulmonary aspergillosis, fungemia (fungal infection in blood), chorioamnionitis (inflammation of the fetal membranes), etc. could be acquired from contaminated food sources, indicating human infections also involve food safety issues [1, 2, 3]. Moreover, outbreaks in commodity-specific food sources such as wheat, corn, or tree nut contaminationby fungi-produced mycotoxins directly affect public health. For instance, aflat are hepatotoxic and/or nephrotoxic carcinogens/mutagens highly detrimental to human or animal health, thus are a serious threat to food safety, security, and food/crop marketability [4; 5]. Therefore, the development of new antimicrobial agents or intervention methods for the control of foodborne pathogens, especially those resistant to conventional antimicrobials, is continually needed. Many antimicrobial agents have been developed from mushroom ingredients [6; 7]. For crop protection, as an example, the natural fungicides strobilurins have been isolated from the basidiomycete _Strobilurins tenacellus_, an agaric fungus known as pinecone cap. Strobilurins are quinone outside inhibitor (QoI) fungicides that interrupt fungal mitochondrial respiration by specifically binding to the quinol oxidation (Qo) site of cytochrome \(b\) in the respiratory chain. While strobilurin-A is the original, natural form of the compound, other synthetic derivatives of strobilurins such as azoxystrobin, kresoxim-methyl, pyracolostrobin, trifloxystrobin, etc., have been developed and commercialized for their higher efficacy, low volatility, and enhanced resistance to UV breakdown [8]. Nevertheless, there have been several reports describing the development of fungal resistance to strobilurins. It has been determined that the function of the intrinsic alternative oxidase (a strobilurin-insensitive terminal oxidase enabling electrons from ubiquinol to bypass Complex III), the point mutation G143A in the cytochrome \(b\) complex, efflux pumps, etc., contributed to fungal insensitivity or resistance to the strobilurin fungicides [9; 10]. Recently, mushrooms have also been potential sources of antimicrobials for food preservation and food safety control [11]. For example, the long-chain glycolipids isolated from the jelly mushroom _Dacrylopinax spathularia_ have been classified as Generally Regarded As Safe (GRAS) molecules by the United States Food and Drug Administration [12], for proposed use as food preservatives against microbial contaminants in select non-alcoholic beverages. Additionally, the methanolic extract of industrially grown basidiomycete _Coriolus versicolor_ exhibited potent antibiotic activity against foodborne bacterium _Salmonella enterica_ serovar Enteritidis [13]. However, despite the increasing consumer demands for safe, natural alternatives to the conventional food preservatives, antimicrobial agents from edible mushrooms have not been fully explored to date for their application in food production, processing, and preservation [14]. Edible mushrooms have been a sustainable source of bioactive compounds, and constituents of certain medicinal mushrooms have emerged as integral ingredients of dietary supplements [15; 16]. For instance, the folk medicinal mushroom _Taiwanafoungus camphonatus_ exerted resistance against obesity, where the mushroom reduced obesity caused by leptin-deficiency and restored intestinal barrier integrity [16]. Several studies have further determined that _T.