ICAR-Directorate of Coldwater Fisheries Research (ICAR-DCFR), Bhimtal, Nainital, Uttarakhand, 263136, India.
ICAR-Indian Agricultural Research Institute, Gauriakarma, Hazaribagh, Jharkhand, 825405, India.
Sci Rep. 2023 Aug 15;13(1):13268. doi: 10.1038/s41598-023-40028-5.
In this study, six isolates of Chryseobacterium balustinum were characterized from diseased rainbow trout fingerlings. The virulence characteristics, pathogenicity, and antimicrobial susceptibility pattern of these isolates were investigated. The bacterium showed positive results for catalase, cytochrome oxidase, and aesculin hydrolysis, while negative results were obtained for DNase, gelatinase, methyl red, Voges-Proskauer's reaction, Simon citrate, Hydrogen sulphide, and starch hydrolysis. Amino acid metabolism analysis revealed the inability to metabolize arginine, lysine, and ornithine decarboxylase. Molecular characterization (16S rRNA) and phylogenetic analysis revealed the test isolates as C. balustinum, closely related to strain WLT (99.85% similarity) and C. balustinum P-27 (99.77%). Virulence assay indicated haemolytic activity and biofilm formation by the test bacterium. The challenge test confirmed moderate pathogenicity in rainbow trout and established Koch's postulates. The clinical manifestations of infection included fin erosion, eye and body surface haemorrhage, exophthalmia, and organ liquefaction. The minimum inhibitory concentrations of various antimicrobials ranged from 1 to > 256 µg mL. The novel synthetic antimicrobial peptides exhibited MICs of 8 to > 256 µg mL, suggesting a potential control method. These findings suggest that C. balustinum is an opportunistic pathogen with moderate pathogenicity in rainbow trout. Further research on the host-pathogen relationship is necessary to understand virulence characteristics and pathogenicity in aquaculture.
在这项研究中，从患病的彩虹鳟鱼苗中分离出了六株黄杆菌属细菌。研究了这些分离株的毒力特征、致病性和抗菌药物敏感性模式。该细菌对过氧化氢酶、细胞色素氧化酶和七叶苷水解呈阳性反应，而对 DNA 酶、明胶酶、甲基红、Voges-Proskauer 反应、西蒙柠檬酸盐、硫化氢和淀粉水解呈阴性反应。氨基酸代谢分析显示不能代谢精氨酸、赖氨酸和鸟氨酸脱羧酶。分子特征（16S rRNA）和系统发育分析表明，测试分离株为黄杆菌属，与菌株 WLT（99.85%相似度）和 C. balustinum P-27（99.77%相似度）密切相关。毒力测定表明测试细菌具有溶血活性和生物膜形成能力。攻毒试验证实了对彩虹鳟的中度致病性，并确立了科赫假设。感染的临床症状包括鱼鳍侵蚀、眼睛和体表出血、眼球突出和器官液化。各种抗菌药物的最低抑菌浓度范围为 1 至>256µg/mL。新型合成抗菌肽的 MIC 值为 8 至>256µg/mL，表明这可能是一种潜在的控制方法。这些发现表明，黄杆菌属是一种机会性病原体，对彩虹鳟具有中度致病性。需要进一步研究宿主-病原体关系，以了解水产养殖中的毒力特征和致病性。
