In this field study, two private Oreochromis niloticus fish farms in El Fayoum and El Sharkia governorates showed signs of septicaemia, with a mortality of 20%–25% between autumn 2018 and summer 2019. Postmortem examination of affected fish revealed loose scales, ulceration in the dorsal part of the head, petechial haemorrhages on the body surfaces, unilateral exophthalmia, and corneal opacity together with congested blood vessels of nearly all fleshy portions of the body fins. Internal examination of the viscera showed congestion of the blood vessels in the kidneys and brain, a dark enlarged spleen, and a liver with a marbled appearance. Fish samples (representing 10% of the fish showing clinical signs) were collected and examined for histopathological and bacteriological examination. Aerococcus viridans was isolated from El Fayoum and El Sharkia governorates at rates of 18.18% and 28.89%, respectively, throughout the year, whereas Enterococcus faecalis was isolated at rates of 81.82% and 71.11%, respectively; seasonal prevalence rate of infection were recorded. Antibiotic sensitivity testing showed that the two microorganisms were resistant to ampicillin, oxolinic acid, nalidixic acid, amikacin, and gentamicin, but they were sensitive to amoxicillin and nitrofurantoin. E. faecalis exhibited resistance to erythromycin and oxytetracycline, whereas A. viridans was sensitive to these agents. To study the pathogenicity of such microorganisms in this fish species, experimental infection and reisolation of both bacterial isolates in O. niloticus was performed to confirm the field isolation. The pathological lesions in different organs of the infected fish were fully recorded.

中文翻译：

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埃及鱼类养殖场对革兰氏阳性细菌绿气单球菌和粪肠球菌的细菌学，分子和病理学研究及其对尼罗罗非鱼的影响

在该田野研究中，El Fayoum和El Sharkia省的两个私人Oreochromis niloticus养鱼场表现出败血病迹象，在2018年秋季至2019年夏季之间的死亡率为20％–25％。对死鱼的死后检查显示鳞片松动，溃疡。头部的背侧部分，体表上的瘀斑出血，单侧性眼球突出症和角膜混浊以及几乎所有身体鳍肉部分的血管充血。内脏的内部检查显示肾脏和大脑的血管充血，脾脏黑色扩大以及外观为大理石的肝脏。收集鱼样品（占显示出临床体征的鱼的10％）并进行组织病理学和细菌学检查。全年从El Fayoum省和El Sharkia省分离出绿气球菌，其分离率分别为81.82％和71.11％，而粪肠球菌的分离率分别为18.18％和28.89％。记录季节性感染率。抗生素敏感性测试表明，两种微生物均对氨苄西林，草酸，萘啶酸，丁胺卡那霉素和庆大霉素具有抗性，但对阿莫西林和硝基呋喃妥因敏感。粪肠球菌展出耐红霉素和土霉素，而甲。翠绿对这些代理人很敏感。为了研究这种微生物在该鱼类中的致病性，进行了实验感染和尼罗罗非鱼中两种细菌分离株的重新分离，以确认田间分离。完整记录了受感染鱼不同器官的病理病变。