Neocitreamicins I and II, novel antibiotics with activity against methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci

Two novel antibiotics, neocitreamicins I and II, were isolated from a fermentation broth of a Nocardia strain. This producing strain was obtained using an in situ diffusion chamber that facilitates the cultivation of soil microorganisms. The structures of neocitreamicins I and II were elucidated using UV MS, and NMR data, and found to be related to the polycyclic xanthone antibiotics of the citreamicin class. The neocitreamicins showed in vitro activity against Gram-positive bacteria including strains of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis.