Comparative Effects of Crude Extracts and Bioactive Compounds from and on Nonspecific Immune Responses and Antibacterial Activity Against sp. in Coculture with Lactic Acid Bacteria in Hybrid Grouper ( ♀ × ♂).

This study investigated the effect of substances on nonspecific immune responses of head kidney leukocytes, the antimicrobial activity against sp., as well as the time-kill of sp. by combining the substances with lactic acid bacteria (LAB) and sp. The substances are hot water extract, powder extract, methanol extract, ethanol extract, hot water extract, powder extract, methanol extract, ethanol extract, and bioactive compounds, namely cytopiloyne, flavonoid, phenol, ethyl caffeate, luteolin, chlorogenic acid, butein, and linoleic acid. The results showed that some of them were nontoxic to the head kidney leukocytes, which can increase the phagocytic rate, phagocytic index, and respiratory burst. These substances were able to inhibit the growth of sp.; they can even completely kill the pathogenic bacteria. The largest of the inhibition zone formed from the EC group at a concentration range of 5-50 µg/mL against , , and with a value of 19.7 ± 0.56, 19.3 ± 1.53, and 20.6 ± 1.53 mm. Furthermore, the time-kill studies showed that the LAB and can completely kill the sp. at 6 h incubation time, mainly in the group of combination with EC.