Assessing multi-drug resistance in Streptococcus agalactiae infecting farmed Nile Tilapia: Findings from Kerala, India

IF 3.3 3区医学 Q3 IMMUNOLOGY

Microbial pathogenesis Pub Date : 2025-05-03 DOI:10.1016/j.micpath.2025.107666

Keerthana Kalathil Maniyappan, Sneha Kalasseril Girijan, Rahul Krishnan, Asha Gopan, Devika Pillai

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Abstract

Streptococcus agalactiae infections in tilapia are indeed a major concern in the global aquaculture industry, leading to significant economic losses. This study describes the isolation, virulence factors, pathogenicity and antibiotic susceptibility pattern of S. agalactiae in cultured Nile tilapia (Oreochromis niloticus) from aquaculture farms in Kerala, India. The diseased fish showed erratic swimming, lethargy, eye opacity, exophthalmia, darkened body, ascites and haemorrhages. Histopathological findings revealed hepatocytic vacuolization and meningitis. Molecular serotyping of the S. agalactiae isolates identified the serotype Ia. In terms of virulence characteristics, the S. agalactiae isolate obtained from tilapia sample had fbsA, cfB and pbp1A/ponA genes, and they were moderate biofilm producers. It is a matter of concern that the isolates were resistant to the tested macrolides, glycopeptides, chloramphenicol, tetracycline, sulphonamides, lincosamides, oxazolidinones and beta lactam group of antibiotics. Pathogenicity of the isolated strain was tested by experimental challenge through intraperitoneal injection of the isolated strain in Nile tilapia.100 %, 80 %, 40 % and 20 % mortality at doses of 1.0 × 10⁸, 1.0 × 10⁶, 1.0 × 10⁴ and 1.0 × 10² CFU/ml, respectively were recorded in the challenged fish. Level of liver enzymes such as Aspartate aminotransferase (AST) and Alanine Aminotransferase (ALT), and glucose were significantly increased compared to that in control. The haematological indices such as RBC and haemoglobin counts were significantly reduced, while WBC count increased in the challenged fish. The haemolysis test on blood agar plate showed beta haemolysis (β). The emergence of multidrug-resistant pathogen S. agalactiae in tilapia farms in the state is an early warning for appropriate preventive measures to be taken to control their spread across farms as tilapia culture is widely popular in the state.

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评估感染尼罗罗非鱼的无乳链球菌的多重耐药性：来自印度喀拉拉邦的发现

罗非鱼的无乳链球菌感染确实是全球水产养殖业的一个主要问题，导致重大的经济损失。本文研究了印度喀拉拉邦养殖尼罗罗非鱼（Oreochromis niloticus）中无乳链球菌的分离、毒力因子、致病性和抗生素敏感性。病鱼游动不稳、嗜睡、眼浑浊、眼突出、体暗、腹水出血。组织病理学结果显示肝细胞空泡化和脑膜炎。无乳链球菌分子血清分型鉴定为Ia型。在毒力特性方面，从罗非鱼样品中分离得到的无乳链球菌具有fbsA、cfB和pbp1A/ponA基因，是中等产膜菌。对大环内酯类、糖肽类、氯霉素类、四环素类、磺胺类、lincosamides类、恶唑烷酮类和内酰胺类抗生素耐药值得关注。通过对尼罗罗非鱼腹腔注射分离菌株的实验攻毒，检测了分离菌株的致病性。剂量分别为1.0 × 108、1.0 × 106、1.0 × 104和1.0 × 102 CFU/ml，致死率分别为100%、80%、40%和20%。肝酶如谷草转氨酶（AST）和丙氨酸转氨酶（ALT）水平和葡萄糖水平与对照组相比显著升高。红细胞和血红蛋白计数等血液学指标显著降低，白细胞计数增加。血琼脂平板溶血试验显示溶血β (β)。由于罗非鱼养殖在该州广泛流行，该州罗非鱼养殖场出现了耐多药病原体无乳链球菌，这是一个早期预警，需要采取适当的预防措施来控制其在养殖场中的传播。

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来源期刊

Microbial pathogenesis 医学-免疫学

CiteScore

7.40

自引率

2.60%

发文量

472

审稿时长

56 days

期刊介绍： Microbial Pathogenesis publishes original contributions and reviews about the molecular and cellular mechanisms of infectious diseases. It covers microbiology, host-pathogen interaction and immunology related to infectious agents, including bacteria, fungi, viruses and protozoa. It also accepts papers in the field of clinical microbiology, with the exception of case reports. Research Areas Include: -Pathogenesis -Virulence factors -Host susceptibility or resistance -Immune mechanisms -Identification, cloning and sequencing of relevant genes -Genetic studies -Viruses, prokaryotic organisms and protozoa -Microbiota -Systems biology related to infectious diseases -Targets for vaccine design (pre-clinical studies)