BLEPHARISMIN PRODUCED BY A PROTOZOAN BLEPHARISMA FUNCTIONS AS AN ANTIBIOTIC EFFECTIVE AGAINST METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS

A ciliated protozoan, Blepharisma japonicum, produces a photosensitive red pigment, blepharismin (BLR). This study showed that the pigment i nhibits the growth of Gram-positive bacteria, such as methicillin-resi stant Staphylococcus aureus (MRSA) resistant to arbekacin (ABK), which is the most effective aminoglycoside antibiotic against MRSA and used world wide. Although the minimum inhibitory concentration (MIG) of BL R to the ABK-resistant MRSA strain was 6.25 mu g/ml in dark, it was de creased to 1.25 mu g/ml by irradiation with white light of 65 W/m(2) f or 30 min, suggesting that the antibacterial activity of BLR is photoa ctivated. Our findings suggested that the antibacterial activity of BL R in dark is due to inhibition of protein synthesis. In addition, we f ound that BLR is bactericidal and enhances synergistically the antibac terial activity of ABK.