Structure-activity studies of echinomycin antibiotics against drug-resistant and biofilm-forming Staphylococcus aureus and Enterococcus faecalis

Four echinomycin antibiotics were isolated from the culture broth of a marine streptomycete, and their structures were determined by a combination of chemical and spectroscopic analyses. Antibiotic activities were measured against drug-resistant and biofilm-forming strains of Staphylococcus aureus and Enterococcus faecalis. Minimum inhibitory concentrations ranging from 0.01 mu M to greater than 14 mu M clearly defined structure-activity relationships for antibiotic potency. Echinomycin was the most active compound with a MIC of 0.03 mu M against methicillin-resistant S. aureus and 0.01 mu M against biofilm-forming E. faecalis. (C) 2009 Elsevier Ltd. All rights reserved.