The innate immune system is also of primary importance in combating infections in fish, including lysozyme and phagocytic cells (Magnadóttir, 2006).
Lysozyme is one of the defensive factors against invasion by microorganisms. It cleaves the -(14) linkages between N-acetylmuramic acid and N-acetylglucosamine in the cell walls of Gram-positive bacteria, thus preventing them from invading (Salton and Ghuysen, 1959; Yano, 1996). Increased
lysozyme activity in the GBS infected group in the present study indicates that lysozyme is an important humoral component of the non-specific immune system.