Isolation and characterization of Streptococcus agalactiae inducing mass mortalities in cultured Nile tilapia (Oreochromis niloticus) with trials for disease control using zinc oxide nanoparticles and ethanolic leaf extracts of some medicinal plants.

IF 2.3 2区 农林科学 Q1 VETERINARY SCIENCES
Ebtsam Sayed Hassan Abdallah, Walaa Gomaa Mohamed Metwally, Soad Abdel Latief Hassan Bayoumi, Moataz Ahmed Mohamed Abdel Rahman, Mahmoud Mostafa Mahmoud
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引用次数: 0

Abstract

Background: Streptococcus agalactiae (Group B streptococcus, GBS) induces a serious infection that can harm not only aquatic life but also humans and other animals. In a fish farm in southern Egypt, Nile tilapia (Oreochromis niloticus) has developed an epidemic with clinical symptoms resembling piscine streptococcosis.

Results: Initial microscopic inspection of the affected fish brain and kidney indicated the presence of Gram-positive cocci. S. agalactiae was effectively isolated and identified using nucleotide homology of the 16S rRNA and species-specific PCR. The partial 16S rRNA sequence was deposited in the GenBank database at the NCBI and given the accession number MW599202. Genotyping using RAPD analysis indicated that the isolates in the present study belonged to the same genotypes and had the same origin. The challenge test, via immersion (9.2 × 107, 9.2 × 106, and 9.2 × 105 CFU/ml for 1 h) or intraperitoneal injection (4.6 × 107, 4.6 × 106, and 4.6 × 105 CFU/fish), elicited clinical symptoms resembling those of naturally infected fish with a mortality rate as high as 80%. The ability to create a biofilm as one of the pathogen virulence factors was verified. Zinc oxide nanoparticles and the ethanolic leaf extracts of nine medicinal plants demonstrated considerable antibacterial activities against the tested S. agalactiae strain with low minimum bactericidal concentrations (MBC) and minimum inhibitory concentrations (MIC). The ethanolic leaf extracts from Lantana camara and Aberia caffra showed potent antibacterial activity with MBC values of 0.24 and 0.485 mg/ml, and MIC values of 0.12 & 0.24 mg/ml, respectively.

Conclusion: This study isolated S. agalactiae from O. niloticus mortalities in a fish farm in Assiut, Egypt. The pathogen persists in fish environments and can escape through biofilm formation, suggesting it cannot be easily eliminated. However, promising findings were obtained with in vitro control employing zinc oxide nanoparticles and medicinal plant extracts. Nevertheless further in vivo research is needed.

诱导尼罗罗非鱼(Oreochromis niloticus)大量死亡的无乳链球菌的分离和特征描述,以及使用纳米氧化锌颗粒和一些药用植物的乙醇叶提取物控制疾病的试验。
背景:无乳链球菌(B 组链球菌,GBS)会引发严重感染,不仅会危害水生生物,还会危害人类和其他动物。在埃及南部的一个养鱼场,尼罗罗非鱼(Oreochromis niloticus)出现了一种流行病,临床症状类似于鱼类链球菌病:结果:对患病鱼的大脑和肾脏进行初步显微镜检查后发现存在革兰氏阳性球菌。利用 16S rRNA 的核苷酸同源性和物种特异性 PCR 技术,有效分离并鉴定了 S. agalactiae。部分 16S rRNA 序列已存入美国国家生物技术研究所(NCBI)的 GenBank 数据库,登录号为 MW599202。利用 RAPD 分析进行的基因分型表明,本研究中的分离物属于相同的基因型,具有相同的来源。通过浸泡(9.2×107、9.2×106 和 9.2×105 CFU/ml,浸泡 1 小时)或腹腔注射(4.6×107、4.6×106 和 4.6×105 CFU/条鱼)进行的挑战试验引起了与自然感染鱼相似的临床症状,死亡率高达 80%。病原体的毒力因素之一是形成生物膜的能力得到了验证。氧化锌纳米粒子和九种药用植物的乙醇叶提取物对测试的 S. agalactiae 菌株具有相当高的抗菌活性,最低杀菌浓度(MBC)和最低抑菌浓度(MIC)均较低。Lantana camara 和 Aberia caffra 的乙醇叶提取物显示出强大的抗菌活性,MBC 值分别为 0.24 和 0.485 毫克/毫升,MIC 值分别为 0.12 和 0.24 毫克/毫升:本研究从埃及阿苏特一家鱼类养殖场的黑线鳕死亡病例中分离出了 S. agalactiae。该病原体可在鱼类环境中存活,并可通过形成生物膜逃逸,这表明它不容易被消灭。不过,利用纳米氧化锌颗粒和药用植物提取物进行体外控制取得了令人鼓舞的结果。不过,还需要进一步的体内研究。
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来源期刊
BMC Veterinary Research
BMC Veterinary Research VETERINARY SCIENCES-
CiteScore
4.80
自引率
3.80%
发文量
420
审稿时长
3-6 weeks
期刊介绍: BMC Veterinary Research is an open access, peer-reviewed journal that considers articles on all aspects of veterinary science and medicine, including the epidemiology, diagnosis, prevention and treatment of medical conditions of domestic, companion, farm and wild animals, as well as the biomedical processes that underlie their health.
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