Evaluations of lactic acid bacteria as probiotics for juvenile seabass Lates calcarifer |
| |
Authors: | Sirirat Rengpipat,Thosaporn Rueangruklikhit,& Somkiat Piyatiratitivorakul |
| |
Affiliation: | Program in Biotechnology, Chulalongkorn University, Bangkok, Thailand; Department of Microbiology, Chulalongkorn University, Bangkok, Thailand; Center of Excellence for Marine Biotechnology, Chulalongkorn University, Bangkok, Thailand; Department of Marine Science, Chulalongkorn University, Bangkok, Thailand |
| |
Abstract: | Lactic acid bacteria (LAB) were isolated from adult, wild‐caught and farmed seabass (Lates calcarifer) intestines for evaluation as possible probiotics using the well agar diffusion method. Five LAB isolates (designated as LAB‐1–5) were found to inhibit Aeromonas hydrophila, a known seabass pathogen. Median lethal concentrations (LC50) of A. hydrophila on juvenile seabass were measured in aquaria. Median lethal concentration values of 7.76, 7.47 and 7.26 log10 CFU mL?1 for 72, 96 and 120 h, respectively, were found. Juvenile seabass (0.6±0.2 g) were cultured in aquaria and fed individual LAB‐1–5 fortified feeds with 7 log10 CFU g?1 LAB. Seabass fed LAB‐4 fortified feed had significantly greater growth (P<0.05) than fish fed other feeds. Seabass fed LAB‐4 also had greater survival, but this was non‐significant (P<0.05). Challenge tests of LAB‐4 fed seabass with A. hydrophila at ~7 log10CFU mL?1 yielded significantly greater survival compared with control seabass (P<0.05). Aeromonas hydrophila infections in seabass were confirmed by observing disease manifestation and by immunohistochemistry techniques. LAB‐4 was preliminarily identified using lactic acid analysis, biochemical and physical characteristics. It was further identified using 16S rDNA sequencing. LAB‐4 was identified as Weissella confusa (identity of 99%). GenBank accession number for the 16S rDNA sequence for LAB‐4 was AB023241. |
| |
Keywords: | probiotics lactic acid bacteria juvenile seabass Lates calcarifer |
|
|