Evaluation of antimicrobial activity of extracts from South African Usnea barbata

Usnea barbata is a lichen of the Usneaceae family that grows epiphytically on trunks and branches of trees. It is widespread in Hogsback, South Africa. Extracts of the lichen were investigated for antimicrobial activity against 10 bacterial and 5 fungal strains by dilution method on solid agar medium. The extracts showed significant activity against the Gram-positive bacteria with minimum inhibitory concentration as low as 0.1 mg/ml on Bacillus subtilis, Enterococcus faecalis, Micrococcus viradans and Staphylococcus aureus. The acetone extract was the most active while the water extract showed the least activity against the microbes. Our findings have validated the use of the lichens for the treatment of various infections in man and livestock.