In vitro and in vivo antibacterial activity of sea anemone-isolated Vibrio parahaemolyticus against Yersinia ruckeri

The overuse of antibiotics has led to increasing concern in bacterial resistance in the fish farming industry. The use of antibiotics has no apparent effect when pathogens form a biofilm. In this study, we evaluated the antibacterial and anti-biofilm properties of sea anemone Stichodactyla haddoni (MW674680)-isolated bacteria (SIB) against Yersinia ruckeri (PTCC1888). Out of 53 SIB extracts, Vibrio parahaemolyticus extract (E-2) displayed the most efficient antibacterial and anti-biofilm activity against Yersinia ruckeri with minimum inhibitory concentration (MIC) and minimum biofilm inhibitory concentration (MBIC) at 200 mu g mL(-1) (P < 0.05). The result was confirmed by FT-IR as well as scanning electron microscopy analysis in which E-2 affected the biofilm formation in Yersinia ruckeri. Besides, the quorum sensing inhibitory activity of E-2 was observed using Chromobacterium violaceum 026 as a reporter strain. The chemical and physical evaluation of E-2 indicated the active components are non-proteinaceous. Gas chromatography-mass spectra analysis of E-2 demonstrated 8 known compounds, mainly Pyrrolo[1,2-a]pyrazine-1,4-dione, hexahydro-3-(2-methylpropyl)- hexahydro-3-(phenylmethyl) (31.85%) and 9,12-Octadecadienoic acid, methyl ester (36.71%). The results from the experimental challenge showed that the administration of E-2 at two safe doses (10 and 25 mg mL(-1)) increased lysozyme and complement activities and survival rates, and decreased intestinal necrosis and goblet cells in zebrafish within 12 days (P < 0.05). This study introduced V. parahaemolyticus (MN563125) as a potent antibacterial and anti-biofilm producer that could be a perfect candidate to control yersiniosis in aquaculture.