Rugulotrosin A is an antibiotic originally isolated from Penicillium. It is active against the Gram-positive bacteria E. faecalis, B. cereus, B. subtilis, and S. aureus with 99% lethal dose (LD99) values of 1.6, 3.1, 5.5, and 200 ug/ml, respectively. Rugulotrosin A is inactive against Gram-negative bacteria.