Naphthacemycins, novel circumventors of β-lactam resistance in MRSA, produced by Streptomyces sp. KB-3346-5. I. The taxonomy of the producing strain, and the fermentation, isolation and antibacterial activities

Abstract

Screening for circumventors of β-lactam resistance in methicillin-resistant Staphylococcus aureus (MRSA) led us to find 17 novel antibiotics, naphthacemycins A1-A11, B1-B4 and C1-C2. The naphthacemycins were isolated from a cultured broth of Streptomyces sp. KB-3346-5 by repeated silica gel column chromatography and HPLC. Naphthacemycins enhanced imipenem activity 100-500 times against MRSA at 0.5 μg ml-1, and naphthacemycins A4-A11 themselves showed MIC50 values of 1-4 μg ml-1 against 22 MRSA strains.