New bisanthraquinone antibiotics and semi-synthetic derivatives with potent activity against clinical Staphylococcus aureus and Enterococcus faecium isolates

The escalation of antibiotic resistance among Gram-positive pathogens presents increasing treatment challenges and requires the development of innovative therapeutic agents. Here, we present the antimicrobial properties of structurally unusual bisanthraquinone metabolites produced by a marine streptomycete and four semi-synthetic derivatives. Biological activities were measured against clinically derived isolates of vancomycin-resistant Enterococcus faecium (VRE), and methicillin-susceptible, methicillin-resistant, and tetracycline-resistant Staphylococcus aureus (MSSA, MRSA, and TRSA, respectively). The most potent antibiotic displayed MIC50 values of 0.11, 0.23, and 0.90 μM against a panel (n = 25 each) of clinical MSSA, MRSA, and VRE, respectively, and was determined to be bactericidal by time-kill analysis.

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