The purpose of this study was to isolate and characterize the disease causative bacterial species from commercially important freshwater fish species, Cirrhinus mrigala. For this purpose, diseased C. mrigala samples were collected both from cultured and wild conditions. From sampled fish, extracted gills, liver, intestine and skin were homogenized in PBS buffer. Bacterial isolation was achieved by inoculating samples on nutrient agar plates using the method of pour plate and streak plate. Maximum total bacterial load was found 3.4 × 10⁵. Bacterial isolates were identified using morphological, physiological and biochemical features. Gram stain, motility, catalase, starch hydrolysis, fermentation, Indole, Methyl red, Voges‐Proskauer and Urease tests were performed for identification. In short, isolated bacteria were identified as Escherichia coli, Staphylococcus aureus, Bacillus cereus and Citrobacter freundii. Pathogenicity was confirmed in healthy fish by the use of reproduced isolate through experimental infection to fulfil Koch's postulates. Variations in organ structures were studied by histopathology and changes that were found to be lesions, tissue degenerations, necrotic and haemorrhages. This study will be supportive in formulating control measures for disease prevention and successful treatment for these pathogenic bacteria.

中文翻译：

---

患病百里香中分离出的细菌性病原体的描述

这项研究的目的是从商业上重要的淡水鱼类Cirrhinus mrigala中分离并鉴定引起疾病的细菌种。为此，从培养条件和野生条件下都采集了患病的C. mrigala样品。从取样的鱼中，将提取的腮，肝，肠和皮肤在PBS缓冲液中匀浆。细菌分离是通过使用倾倒平板和条纹平板的方法在营养琼脂平板上接种样品来实现的。发现最大总细菌载量3.4×10 ⁵。使用形态，生理和生化特征鉴定细菌分离物。进行革兰氏染色，运动性，过氧化氢酶，淀粉水解，发酵，吲哚，甲基红，Voges-Proskauer和脲酶测试以进行鉴定。简而言之，分离出的细菌被鉴定为大肠杆菌，金黄色葡萄球菌，蜡状芽孢杆菌和弗氏柠檬酸杆菌。。通过使用经实验感染的繁殖分离株来满足科赫的假设，可以确认健康鱼的致病性。通过组织病理学研究了器官结构的变化，发现了病变，组织变性，坏死和出血。这项研究将为制定预防措施和成功治疗这些病原菌提供支持。