ANTIMICROBIAL AND THERAPEUTIC POTENTIALS OF EXTRACTS FROM SELECTED MUSHROOMS AGAINST SOME PATHOGENIC MICROORGANISMS

Abstract

Epidemics of infection due to drug resistance and unknown microbial organisms remain the public health concern. Consequently, there is the strong need for renewed strategies on treatment and prevention in which fungi because of its great biodiversity cannot be overlooked. Investigations were conducted to assay the antimicrobial and therapeutic potentials of selected endophytic fungi as well as edible and poisonous mushrooms. Employing molecular techniques, eighteen (18) fungal species were identified. Methanol and hot water extracts of five mushrooms and three endophytic fungi species were investigated for their antimicrobial activity using agar well diffusion and disc diffusion methods against six clinical bacterial and two fungal pathogens. The sensitivity patterns of typed cultures to the fungal extracts were also evaluated. Standard antibiotics (0.5 μg Ciprofloxacin) used against the bacteria showed the highest inhibitory activity (27 mm) against Pseudomonas aerugenosa and the least (13 mm) against Staphylococcus aureus. The standard antifungal agent (10 mg/ml Fluconazole) showed highest inhibition (15 mm) against Aspergilus flavus and least (9 mm) against Candida albicans. Mushroom extracts showed antibacterial activity ranging from 6 to 18 mm and antifungal activity of 3 to 12 mm. Endophytic fungal extracts induced broad spectrum antimicrobial activity with zones of inhibition ranging from 7 to 12 mm. At 200 μg/ml concentration the bioactive fractions obtained from methanol extract of Pleurotus ostreatus and Trametes versicolor produced appreciable broad spectrum antimicrobial activity. The mushroom extracts showed Minimum Inhibitory Concentration (MIC) ranging from 6.25 to 100 mg/ml and Minimum Bactericidal Concentration (MBC) ranging from 50 to 100 mg/ml. The phytochemical constiuents such as terpenoids, cardiac glycosides and steroids were significantly higher (P < 0.05) in hot water extract when compared with methanol extract. Total viii Phenolic constituents, antioxidants and scavenging capacity against free radicals were in appreciable amount in all the fungal species. Phomopsis liquidambaris hosted in the leaf and petiole of Bryophyllum pinnatum had the best scavenging capacity and the Inhibitory Concentration (IC50) against Diphenyl Picry Hydrazyl was 0.04±0.01. Total phenol and free radical scavenging potency was higher in P. ostreatus as compared with T. versicolor. The Fourier Transform-Infrared (FT-IR) Spectra and Gas Chromatography Mass Spectra (GC-MS) revealed the bioactive compounds inherent in the mushroom species. The in vivo study of P. ostreatus was conducted on Staphylococcus aureus infected Wistar albino rats of weight range 63 g - 114 g. P. ostreatus methanol extract Lethal dose for 50 % of the animals which was greater than 5000 mg/kg (LD 50 > 5000 mg/kg) was used to determine the graded doses for therapeutic study. Infected untreated and treated rats with 625 mg/kg body weight extract (low dose) had skin ulceration while moderate to high dose treatment produced apparently healthy skin. Bacterial count in blood culture after 7 days post treatment was significantly high in the untreated and low dose (32.00 x 104 ± 6.10b; 43.40 x 104 ± 6.20b Cfu/ml) P < 0.05. Haematological and serum biochemical values were not significantly P < 0.05 affected. Chronic administration of P. ostreatus had no ill effect on any of the vital organs including the heart, kidney, liver, lungs and spleen. This could form a basis for the production of a novel antimicrobial of commercial value.