| 钟小飘,陈政思,李一,等.珍珠龙胆石斑鱼(Epinephelus fuscoguttatus♀×E.lanceolatu♂) 源美人鱼发光杆菌的分离鉴定与致病性分析[J].广东农业科学,2025,(4-5):- |
| Isolation, identification and pathogenicity analysis of Photobacterium from pearl gentian grouper (Epinephelus fuscoguttatus♀×E.lanceolatu♂) |
| 投稿时间：2024-11-18 修订日期：2025-07-02 |
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| Abstract: |
| Abstract: 【Objective】 This study aimed to isolate and identify the pathogenic bacteria from diseased Pearl Gentian Grouper (Epinephelus fuscoguttatus♀×E. lanceolatu♂),, characterizing the isolate’s species, physiological and biochemical properties, drug sensitivity profiles, and pathogenicity, thereby providing a theoretical foundation for disease prevention and control. 【Methods】 Diseased groupers were collected from a farm in Zhanjiang City. Under aseptic conditions, a dominant bacterial strain (OR539201) was isolated from the spleen. The morphological observation, 16S rRNA gene sequence analysis, physiological and biochemical identification of this isolate were performed. Further analyses including drug susceptibility testing and regression infection experiments, with bacterial loads quantified in the spleen and liver and virulence genes were also carried out.【Results】 The results of morphological observation, 16S rRNA sequence analysis and physiological and biochemical identification indicated that the strain OR539201 was belonged to Photobacterium damselae subsp. damselae. The strain formed circular colonies with rounded, full, and smooth morphology when grow upon the LB agar. Phylogenetic analysis of the 16S rRNA gene revealed a close relationship between this strain and Photobacterium damselae, which are both belonging to the genus Vibrio. Biochemical tests showed positive reactions for oxidase, urea, glycerol, and lysine, while salicin, aesculin, but negative reaction for mannitol. The. drug sensitivity test revealed a varying degrees of resistance to different antibiotics, with moderate sensitivity to polymyxin, butanacana, ceftriaxone, and sensitivity to 13 antibiotics including ofloxacin, ciprofloxacin, and cefalexin. Regression infection experiments demonstrated that this strain possesses significant pathogenic effects on grouper, inducing surface ulcers, red proliferative nodules, liver enlargement, intestinal erosion, and brain redness that were consistent with natural disease manifestations. Bacterial counts in the spleen and liver of groupers in the experimental group were significantly higher than those in the control group, confirming the presence of luminous Bacillus mermaidis. The virulence gene detection results show that the strain possesses the gene (plpV) related to phospholipase activity.【Conclusion】This study isolated and identified a potential pathogen from diseased groupers successfully, which was identified as Luminous Bacillus mermaidis. The strain exhibited significant pathogenicity that could induced severe lesions and fish deaths. |
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