Correlation between bacteria in feed pellets and diseases of cultured turbot Scophthalmus maximus

White feces syndrome is a kind of common and ubiquitous disease in industrial farm of turbot Scophthalmus maximus, which has resulted in massive mortalities and lots of economic losses. Therefore, the correlation between bacteria in feed pellets and diseases of cultured turbot was investigated in 2006. Investigations revealed that three farms of turbot, Penglai (A), Laizhou (B) and Weihai (C) located in Shandong Province, suffered from severe white feces disease. In order to find out the real origin of the pathogenic bacteria, the sicken turbot, water supply, pond water and feed pellets were investigated. Morphological comparison showed that the strain BB-1 from the sicken turbot had the highest similarity to the strain KL-1 from the pellets. API-ID32E and 16S rRNA sequence analyses indicated that BB-1 was the same to KL-1, belonging to genus Pseudoalteromonas sp. Artificial infection experiments indicated that both BB-1 and KL-1 can cause badly white feces disease for healthy turbot, and the clinical signs were similar to the naturally infected turbot. It can be concluded that the bacteria separated from the feed pellets were the real causative agents of white feces syndrome. Drug sensitivity test was also carried out for KL-1 and BB-1, which provided a way to control the disease.