First Isolation and Identification of Shewanella xiamenensis from Diseased Nile Tilapia(Oreochromis niloticus L.)

A gram-negative, motile, and rod-shaped bacterium, strain JF02, was isolated from the liver of diseased GIFT （ genetically improved farmed tilapia） in Hainan, China. The strain JF02 was lethal to GIFT, and most GIFT infected with JF02 exhibited the same clinical signs, such as black body, pale or focally necrosis of the gills, scale shedding, fin rot, liver hyperemia, and hydroabdomen. The 16S rRNA gene sequences of strain JF02 showed 99.7% similarity with that of Shewanella xiamenensis strain S4^T. In addition, the gyrB gene sequences of strain JF02 showed 99.0% similarity with that of S. xiarrvenertsis strain S4^T. Combining the results of morphological, physiological and biochemical characteristics, the isolated strain JF02 was confirmed to be S. xiamenensis. The chemotherapeutic antibiotics tests showed that the strain JF02 was sensitive to most antibiotics except for several common antibiotics that were frequently used in human medicines and treatment of bacterial diseases of fish, indicating that the strain JF02 has obtained many antibiotic resistance genes due to the long-term abuse of antibiotics in aquaculture. In this paper, it was the first time to report that the S. xiamenensis may be a potential pathogen for GIFT. It is time to promote awareness of the potential harm of this strain to the health of human and aquatic animals.