Dextran-Conjugated Lysozymes Inhibit the Growth of Shigella sonnei and Viral Hemorrhagic Septicemia Virus

Lysozyme is well known as a natural antimicrobial agent, but its function is limited in that it only combats Gram-positive bacteria. We investigated the inhibitory effects of dextran-conjugated lysozymes (DLs) against some strains of Gram-negative bacteria and viral hemorrhagic septicemia virus (VHSV). The Maillard reactions of the DL were performed at various pHs (3.0, 7.0, and 8.5) in the presence of saturated KBr solution for 1, 3, 5, 7, and 9 days. The growth inhibition effects against Gram-negative bacterial strains, such as Escherichia coli, Vibrio parahaemolyticus, Pseudomonas aeruginosa, Shigella sonnei, and Shigella flexneri were found only in some DLs. DLs incubated at pH 7.0 for 9 days strongly inhibited growth of S. sonnei (92.9%). Fathead minnow (FHM) cells were infected with VHSV. DLs treated at all pHs for 1 day resulted in more than 80% viability of VHSV-infected FHM cells. The results of this study suggest that our DLs can be useful in food preservatives, pharmaceuticals, or aquatic feed due to their inhibitory effects against pathogenic bacteria and viral infections.