A semi-synthetic cyclic lipopeptide antibiotic isolated form the bacterium Streptomyces roseosporus with broad-spectrum anitbiotic activity against Gram-positive bacteria. Daptomycin has a distinct mechanism of action, in which it binds to bacterial membrane and causes rapid depolarization of the cell membrane due to calcium-dependant potassium efflux; the loss of membrane potential leads to inhibition of DNA, RNA and protein synthesis, resulting in bacterial cell death. This agent does not penetrate the outer membrane of gram-negative bacteria.