| 英文摘要 |
This study investigated bacterial flora of crab ( Scylla sp. ) imported from Sri Lanka.Philippine, Viet Nam, Indonesia and Hai-Nan of China. The dominant bacterial species isolated and identified were Aeromonas hydrophila , Pseudomonas sp. ,Streptococcus sp. ,Vibrio alginolyticus and V. parahaemolyticus. Similar bacterial flora were also isolated and identified in local crab (Scylla sp.).However, the dominant bacterial species diseased local crab were Vibrio alginolyticus and V. parahaemolyticus, followed by lactococcus sp. and Streptococcus sp., with LD50 valves of 1.6-4.2×104,2.4-3.8×104,3.5-6.5×105 and 2.8-7.6×104 colony forming unit/g body weight,respectively.The total bacterial counts and total Vibrio counts in water raising crabs fed with trash fish were at least 10-fold higher than those of crabs fed with artificial feed. The survival rate of the latter was better than the former. The addition of 2% β-1,3 glucan to both group of diet could increase survival rate and hemolymph SOD activity of the crab.In addition, the application of probiotics could improve water qualify and survival rate.Of those,the use of Rhodospirillaceae sp. Exhibited better results than Bacillus subtilis.
Keywords: Scylla sp., bacterial flora,probiotics,pathogen |