Comparative Effects of Crude Extracts and Bioactive Compounds from Bidens pilosa and Bidens alba on Nonspecific Immune Responses and Antibacterial Activity Against Vibrio sp. in Coculture with Lactic Acid Bacteria in Hybrid Grouper (Epinephelus fusco

This study investigated the effect of substances on nonspecific immune responses of head kidney leukocytes, the antimicrobial activity against <i>Vibrio</i> sp., as well as the time-kill of <i>Vibrio</i> sp. by combining the substances with lactic acid bacteria (LAB) and <i>Pediococcus</i> sp. The substances are <i>B. pilosa</i> hot water extract, <i>B. pilosa</i> powder extract, <i>B. pilosa</i> methanol extract, <i>B. pilosa</i> ethanol extract, <i>B. alba</i> hot water extract, <i>B. alba</i> powder extract, <i>B. alba</i> methanol extract, <i>B. alba</i> 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 <i>Vibrio</i> 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 <i>V. parahaemolyticus</i>, <i>V. alginolyticus</i>, and <i>V. harveyi</i> 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 <i>P. acidilactici</i> can completely kill the <i>Vibrio</i> sp. at 6 h incubation time, mainly in the group of combination with EC.