ANTIMICROBIAL PROPERTIES OF NATIVE ULSTER MACROFUNGI (MUSHROOMS AND TOADSTOOLS) TO CLINICAL PATHOGENS

Editor,

Previously, our research group has reported in the UMJ on various traditional Ulster cures and remedies (January 2009)¹ and on the physiological basis of the antibacterial activity emulating such cures and remedies (January 2009)². In addition, we have examined the antimicrobial properties of sphagnum moss and its role in the Great War 1914-1918, relating to bandage preparation and wound dressings.³ To date, we have not examined the antimicrobial properties of native macrofungi, namely the mushrooms and toadstools and therefore, it was the aim of the current study to examine the activity of native Ulster macrofungi on clinical bacterial and fungal pathogens.

Twenty-two species of native macrofungi were collected from woodlands throughout Northern Ireland (Table 1). Lentinula edodes (Shiitake mushroom) was also examined, given its popularity as a constituent of Asian (mainly Japanese) cuisine. Formal identification of all macrofungi examined was made by PCR-DNA techniques, employing fungal 18S rDNA universal ITS 1 and ITS 4 primers (ITS1: TCC GTA GTT GAA CCT GCG G and ITS4: TCC TCC GCT TAT TGA TAT GC). Aqueous and protein extracts (approx.1mg/ ml) were obtained from freeze-dried preparations of each fungus. Six bacterial and one fungal pathogen were examined in this study (Table 1), including the Gram-positive bacteria (Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus (methicillin-sensitive), Staphylococcus aureus (methicillin-resistant), the Gram-negative bacteria (E. coli O157, Klebsiella aerogenes, Pseudomonas aeruginosa) and the fungal pathogen, Aspergillus flavus. All isolates were obtained from the HSC MicroARK Northern Ireland Microbiology Repository, located at the Northern Ireland Public Health Laboratory, Belfast City Hospital (http://www. microark.com). Antimicrobial properties were determined on each fungal extract/pathogen combination by standard disk diffusion assay.

Table 1.

Antimicrobial activity of aqueous and protein extracts of 23 macrofungi against clinical pathogens

	Aqueous Extract	PPER* Extract
Agaricus augustus		Listeria monocytogenes
Agaricus bisporus
Amanita sp.	Staphylococcus aureus, MRSA**
Boletus chrysenteron	Staphylococcus aureus	Listeria monocytogenes
Clitocybe sp.	Staphylococcus aureus, MRSA	Listeria monocytogenes
Coprinus comatus	Bacillus cereus, E. coli O157, Klebsiella pneumoniae Listeria monocytogenes, MRSA, Pseudomonas aeruginosa
Gymnopilus junonius	Klebsiella pneumonia, Listeria monocytogenes, MRSA	Listeria monocytogenes
Gymnopus confluens		Listeria monocytogenes
Hygrocybe nigrescens		Listeria monocytogenes, Aspergillus flavus,E. coli O157
Hypholoma fascicularis	Listeria monocytogenes
Inocybe geophylla	Staphylococcus aureus	Listeria monocytogenes, Aspergillus flavus
Laccaria amethystine	Staphylococcus aureus, MRSA
Lentinula edodes	Aspergillus flavus, Bacillus cereus, E. coli O157, Klebsiella pneumoniae, Listeria monocytogenes, MRSA, Pseudomonas aeruginosa
Leucopaxillus tricolor	Bacillus cereus, E. coli O157, Klebsiella pneumoniae, Listeria monocytogenes, MRSA, Pseudomonas aeruginosa, Staphylococcus aureus	Aspergillus flavusListeria monocytogenes
Mycena rosea	MRSA, Staphylococcus aureus	Aspergillus flavus, E. coli O157, Listeriamonocytogenes
Mycena sp.		E. coli O157, Listeria monocytogenes
Psathyrella candolleana	Bacillus cereus
Pseudotrametes gibbosa	MRSA, Staphylococcus aureus
Russula cyanoxantha		Aspergillus flavus, Listeria monocytogenes
Russula nigricans	MRSA, Staphylococcus aureus
Russula parazurea		Listeria monocytogenes
Russula sp.		Listeria monocytogenes
Trametes versicolor	MRSA, Staphylococcus aureus

Where no value is recorded there was no inhibition in any of the clinical pathogens tested

*PPER = Plant Protein Extraction Reagent

**MRSA = methicillin-resistant Staphylococcus aureus

All native fungi, except for Agaricus bisporus (the common mushroom) demonstrated antimicrobial activity against at least one of the extracts to one of the clinical pathogens tested (Table 1). Two native fungi, Coprinus comatus and Leucopaxillus tricolor were active against all of the pathogens tested. Lentinula edodes (Shiitake mushroom) was also active against all of the pathogens tested. Overall, aqueous extracts were more antimicrobial than the protein extracts examined.

Coprinus comatus is commonly seen in Northern Ireland (Figure 1a) and is sometimes known as shaggy ink cap, lawyer’s wig, or shaggy mane, due to the white cap of the fungus being covered in scales. Other recent studies have also shown this fungal species to exhibit potent antimicrobial properties.⁴ Leucopaxillus tricolor (Figure 1b) is found

Fig 1a.

Coprinus comatus: Dick Culbert, B.C., Canada

growing in woodland litter and is composed of three coloured components, namely a brown cap, yellow gills and a white stem, hence the epiphet name, tricolor. Lentinula edodes (Figure 1c) is a common constituent of Asian cuisine and has been shown previously to have antimicrobial properties.

Fig 1b.

Leucopaxillus tricolor: Eva Skific (Evica)

Antimicrobial resistance (AMR) has now emerged as a major global public health problem. Locally in Northern Ireland, the extremes of AMR manifest as multi- and pan-resistant Gram- negative respiratory infections in patients with cystic fibrosis (CF), particularly associated with Pseudomonas aeruginosa and Burkholderia cenocepacia, which can cause a treatment dilemma due to a shortage of active antibiotics.

In conclusion, this study has identified extracts from native local macrofungal species to have an antimicrobial activity against several clinical pathogens. Given the need to search for novel antimicrobial compounds coupled with the agrarian background of Northern Ireland’s economy, further work should be undertaken to identify other local sources of antimicrobials and a mechanism established amongst the relevant government agencies, academia and patient groups, to help such novel compounds enter into the drug discovery pathway, so that any potential medicinal value can be fully exploited.

Fig 1c.

Lentinula edodes: Fankenstoen from Portland, Oregon, USA