In the study, Aeromonas strains (n = 12) were isolated from moribund grass carp fry reared in the cage culture unit from the Central Himalayan region of India. They were identified as Aeromonas veronii, by biochemically and 16S rRNA analysis. The experimental bath infection of grass carp fry was performed using A. veronii GCAFBLC 228, one of the 12 isolates at cell concentrations 10⁶ and 10⁸ CFU mL⁻¹. The infected fry showed varied behavioural characteristics followed by tail rot, black pigmentation and hemorrhage in the body 48–96 h post infection. The post bath challenged demonstrated maximum mortality (23%) at cell concentration 10⁸ CFU mL⁻¹ during 10^th and 12th day. Histopathology revealed hypertrophy, hyperplasia, fusion of gill lamellae, detachment and epithelial cell detachment in gill, swelling of hepatocytes, granular deposition in liver and tubular degeneration and yellow pigmented macrophage aggregates in the kidney. The in vitro assays for virulence traits recorded that A. veronii GCAFBLC 228 was β-haemolytic having strong cell surface hydrophobicity (CHS) characteristic (> 50%), precipitated after boiling, produced slime, non-suicidal and bound to crystal violet. The antibiogram showed that the strain was susceptible to ciprofloxacin (5 μg), cefotaxime (30 μg), ceftazidime (30 μg), cefoxitin (30 μg), ceftriaxone (30 μg), chloramphenicol (30 μg) and tetracycline (30 μg). Negative staining transmission electron microscopy revealed presence of the lateral flagellum-like structure and cell adherence possibly could be correlated with the pathogenicity of A. veronii GCAFBLC 228. The further investigation is warranted to study the transmission, pathogenesis and epidemiology of A. veronii GCAFBLC 228 to develop the best health management practice for cage farmed fish.

在该研究中，从印度喜马拉雅中部地区网箱养殖单元养殖的垂死草鱼苗中分离出气单胞菌菌株（n = 12）。通过生化和16S rRNA分析，它们被鉴定为维罗单胞菌。使用A. veronii GCAFBLC 228对草鱼鱼苗进行实验性沐浴感染，这是细胞浓度为10 ⁶和10 ⁸  CFU mL ^-1的12 个分离株之一。受感染的鱼苗表现出不同的行为特征，感染后 48-96 小时出现尾部腐烂、黑色色素沉着和体内出血。在细胞浓度为 10 ⁸  CFU mL ^{-1 时，受}攻击的浴后表现出最大死亡率 (23%)在^第10天和^第12 天。组织病理学显示肥大、增生、鳃片融合、鳃脱离和上皮细胞脱离、肝细胞肿胀、肝脏颗粒沉积和肾小管变性和黄色色素巨噬细胞聚集体。毒力性状的体外测定记录了A. veroniiGCAFBLC 228 是具有强细胞表面疏水性 (CHS) 特性 (> 50%) 的 β-溶血性物质，煮沸后沉淀，产生粘液，非自杀性并与结晶紫结合。抗菌谱显示该菌株对环丙沙星（5 μg）、头孢噻肟（30 μg）、头孢他啶（30 μg）、头孢西丁（30 μg）、头孢曲松（30 μg）、氯霉素（30 μg）和四环素（30 μg）敏感. 负染色透射电子显微镜显示的存在横向鞭毛状结构和细胞粘附可能可与致病性相关联维罗纳A. GCAFBLC 228.进一步调查是必要的，研究的传输，发病机制和流行病学A.维罗纳 GCAFBLC 228 制定网箱养殖鱼类的最佳健康管理实践。