Daptomycin eluted from calcium sulfate appears effective against Staphylococcus.

The emergence of resistant strains of Gram-positive organisms in osteomyelitis creates treatment challenges. Daptomycin is an antibiotic that shows promise for treating some resistant strains of Gram-positive infections; however, it has not been widely used clinically for the treatment of osteomyelitis. We determined whether daptomycin eluted from calcium sulfate-a local delivery vehicle used for the treatment of osteomyelitis-retained activity against Gram-positive bacteria. Daptomycin was mixed with calcium sulfate hemihydrate, with both laboratory powder and a commercial kit, to form a hardened pellet. Daptomycin was eluted from calcium sulfate and retained its ability to inhibit bacterial growth of Staphylococcus aureus and Staphylococcus epidermidis for eluates gathered up to 28 days. Our preliminary data demonstrates sterilized pellets with daptomycin retained their ability to inhibit bacterial growth of certain strains of Gram-positive organisms.