Investigation of the inhibitory ability of Melaleuca spp. leaf extract on Vibrio spp. isolated from the intestine of white-leg shrimp infected by white feces disease

White feces disease (WFD) is a significant problem in white-leg shrimp farming, mainly caused by gut microbiota imbalance and the overgrowth of Vibrio spp., especially Vibrio parahaemolyticus. Vibrio colonies were isolated and cultured on thiosulfate citrate bile salts sucrose (TCBS) medium, and had typical morphological characteristics, including a round, convex shape with yellow or green pigmentation. Using a specific primer, the research identified ten V. parahaemolyticus strains and 13 Vibrio spp. strains. Notably, the extraction yields of Melaleuca using methanol were 10.73% and exhibited significant antibacterial activity at concentrations ranging from 25 to 100 mg/mL. Melaleuca extraction shows effect inhibit V. parahaemolyticus A2.1 and A3, with a halo diameter of 5.67 mm at 100 mg/mL. The Melaleuca leaf extract was qualitatively characterized by using gas chromatography-mass spectrometry. The extract contained 13 compounds, including methirol, allyl pentanoate, 1,2,5-hexanetriol, 3,3-diethoxy-1-propyne, tert-butyl hydroperoxide, eucalyptol, cis-beta-ocimene, eugenol methyl ether, β-caryophyllene, α-craryophyllene, α-cubebene, α-farnesene, and caryophyllene oxide. These compounds indicated that Melaleuca leaf extract could be a natural alternative to control Vibrio populations in shrimp ponds, restore intestinal microbiota balance, reduce WFD incidence, and improve shrimp health. Further studies should focus on identifying compounds in the extract against V. parahaemolyticus and investigate shrimp growth when supplemented with the extract.