(-)-Mycousnine is a microbial metabolite and derivative of usnic acid originally isolated fromM. nawaethat has antibacterial and antifungal activities.1,2It is active against the Gram-positive bacteriaB. subtilis,K. rhizophila, andS. aureus(MICs = 4, 8, and 4 g/ml, respectively) but not the Gram-negative bacteriaE. coli,S. typhimurium, andK. pneumoniae(MICs = >128 g/ml for all).2(-)-Mycousnine is also active against the fungiT. mentagrophytes,T. rubrum, andC. albicans(MICs = 25, 25, and 100 μg/ml, respectively).1