Nargenicin (CP-47,444, CS-682) is a 28 carbon macrolide with a fused tricyclic core that has in addition a unique ether bridge. The polyketide antibiotic was isolated from Nocardia argentinensis. Nargenicin is effective towards gram-positive bacteria and been shown to have strong antibacterial activity against Staphylococcus aureus, including strains that are resistant to methicillin. It has also been shown to induce cell differentiation and inhibit cell proliferation in a human myeloid leukemia cell line.