LIPOPOLYSACCHARIDES (LPS) FROM CELL WALLS OF Vibrio alginolyticus AS AN IMMUNOSTIMULANT ON HYBRID GROUPER SEEDS

In hybrid grouper cultivation, disease outbreaks are being increasingly reported as a major constraint to be the sustainable growth of production. Many diseases are linked to the stress condition associated with the intensification systems of farming and the degradation of the environmental biome quality. In poor conditions, larval, seeds and spawner of fish are often opportunistically infected by parasites, viruses and bacterial. Among the pathogen vibriosis is a well-known cause of serious problems in the aquaculture industry with a worldwide occurrence and cause the most severe economic losses. Vibrio alginolyticus is a known agent that cause severe haemorrhagic septicemia and gastroenteritis syndrome. Although chemotherapy is quite popular to treat or prevent the bacterial infections, frequent use of chemotherapeutic agents has allowed for the development of drug-resistant strains and led to allergy and toxicity in humans. Therefore, the use of  lipopolysaccharides from cell walls of V. alginolyticus to stimulate and enhance the immune responses has now become urgent.

A serial of experiments in order to evaluate the effectiveness of lipopolysaccharide (LPS) that extracted from cell walls of Vibrio alginolyticus have been conducted in Pathology Laboratory of Institute for Mariculture Research and Development, Gondol, Bali. Commercial LPS was also used in this study as a comparison. The LPS was delivered by injection intra-muscularly with concentration of 0.1 mL/fish. Survival at the end of experiment (90 days) and following challenge with live V. alginolyticus and titer antibody values were observed.

LPS were effective to increase titer antibody values and survival rates of hybrid grouper fish. The titer antibody values of fish after 90 days rearing period were 128 (LPS V. alginolyticus), 64-128 (commercial LPS), and only 4 in the control fish. The survival rates at the end of experiment were 88.67±3.62% (LPS V. alginolyticus), 85.22±5.93% (commercial LPS), and only 50.13±6.11 % in the control group. RPS of fish following challenged with live V. alginolyticus were 77.46% in the received LPS from V. alginolyticus and 71.12% in the fish received commercial LPS. It is suggested that LPS effective to increase immunity of grouper fish against bacterial infection.