First insights into Weissella tructae infections in rainbow trout (Oncorhynchus mykiss) in Vietnam: Bacterial characterization, pathogenicity and antimicrobial susceptibility

Weissellosis has emerged as a significant disease impacting farmed rainbow trout (Oncorhynchus mykiss), resulting in high global mortality rates. In the summer of 2023, an outbreak in Northern Vietnam's rainbow trout farms was linked to Weissellosis, with mortality rates ranging from 20 % to 60...

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Main Authors: Doan Thi Nhinh, Dang Thi Hoa, Tran Thi Trinh, Mai Van Tung, Nguyen Thi Huong Giang, Kim Van Van, Truong Dinh Hoai
Format: Article
Language:English
Published: Elsevier 2025-09-01
Series:Aquaculture Reports
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Online Access:http://www.sciencedirect.com/science/article/pii/S2352513425003412
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author Doan Thi Nhinh
Dang Thi Hoa
Tran Thi Trinh
Mai Van Tung
Nguyen Thi Huong Giang
Kim Van Van
Truong Dinh Hoai
author_facet Doan Thi Nhinh
Dang Thi Hoa
Tran Thi Trinh
Mai Van Tung
Nguyen Thi Huong Giang
Kim Van Van
Truong Dinh Hoai
author_sort Doan Thi Nhinh
collection DOAJ
description Weissellosis has emerged as a significant disease impacting farmed rainbow trout (Oncorhynchus mykiss), resulting in high global mortality rates. In the summer of 2023, an outbreak in Northern Vietnam's rainbow trout farms was linked to Weissellosis, with mortality rates ranging from 20 % to 60 %, prompting an investigation into the causative agent. A total of 106 diseased fish exhibiting panophthalmitis and hemorrhagic eyes were collected from 25 affected farms. Twenty-five representative isolates, each sourced from a different farm, were identified as Weissella tructae through phenotypic and biochemical characterisation, PCR, and 16S rRNA sequencing. Challenge experiments indicated a relatively high virulence of W. tructae in rainbow trout weighing 35–40 g, with LD₅₀ values estimated at 1.2 × 10⁴ CFU/fish. Histopathological examination revealed significant tissue damage, including hemorrhages in the brain, spleen, and kidney. Antimicrobial susceptibility testing of eight antibiotics authorized for use in Vietnam showed the lowest minimum inhibitory concentration (MIC) values for Amoxicillin, Amoxicillin-Clavulanic Acid, and Erythromycin (0.06–1 mg/L). In contrast, most isolates exhibited MIC values of ≥ 512 mg/L for Sulfamethoxazole/Trimethoprim. This study represents the first report of Weissellosis in Vietnamese rainbow trout, highlighting the geographic expansion of the disease and underscoring the urgent need for effective strategies to prevent and control this pathogen.
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spelling doaj-art-23cedfb550714d9db0b7d753ce702bbc2025-08-20T04:00:32ZengElsevierAquaculture Reports2352-51342025-09-014310295510.1016/j.aqrep.2025.102955First insights into Weissella tructae infections in rainbow trout (Oncorhynchus mykiss) in Vietnam: Bacterial characterization, pathogenicity and antimicrobial susceptibilityDoan Thi Nhinh0Dang Thi Hoa1Tran Thi Trinh2Mai Van Tung3Nguyen Thi Huong Giang4Kim Van Van5Truong Dinh Hoai6Faculty of Fisheries, Vietnam National University of Agriculture, Hanoi 131004, Viet NamFaculty of Fisheries, Vietnam National University of Agriculture, Hanoi 131004, Viet NamFaculty of Fisheries, Vietnam National University of Agriculture, Hanoi 131004, Viet NamFaculty of Fisheries, Vietnam National University of Agriculture, Hanoi 131004, Viet NamFaculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi 131004, Viet NamFaculty of Fisheries, Vietnam National University of Agriculture, Hanoi 131004, Viet NamFaculty of Fisheries, Vietnam National University of Agriculture, Hanoi 131004, Viet Nam; Corresponding author.Weissellosis has emerged as a significant disease impacting farmed rainbow trout (Oncorhynchus mykiss), resulting in high global mortality rates. In the summer of 2023, an outbreak in Northern Vietnam's rainbow trout farms was linked to Weissellosis, with mortality rates ranging from 20 % to 60 %, prompting an investigation into the causative agent. A total of 106 diseased fish exhibiting panophthalmitis and hemorrhagic eyes were collected from 25 affected farms. Twenty-five representative isolates, each sourced from a different farm, were identified as Weissella tructae through phenotypic and biochemical characterisation, PCR, and 16S rRNA sequencing. Challenge experiments indicated a relatively high virulence of W. tructae in rainbow trout weighing 35–40 g, with LD₅₀ values estimated at 1.2 × 10⁴ CFU/fish. Histopathological examination revealed significant tissue damage, including hemorrhages in the brain, spleen, and kidney. Antimicrobial susceptibility testing of eight antibiotics authorized for use in Vietnam showed the lowest minimum inhibitory concentration (MIC) values for Amoxicillin, Amoxicillin-Clavulanic Acid, and Erythromycin (0.06–1 mg/L). In contrast, most isolates exhibited MIC values of ≥ 512 mg/L for Sulfamethoxazole/Trimethoprim. This study represents the first report of Weissellosis in Vietnamese rainbow trout, highlighting the geographic expansion of the disease and underscoring the urgent need for effective strategies to prevent and control this pathogen.http://www.sciencedirect.com/science/article/pii/S2352513425003412Weissella tructaePathogenicityAntimicrobial susceptibilityRainbow troutVietnam
spellingShingle Doan Thi Nhinh
Dang Thi Hoa
Tran Thi Trinh
Mai Van Tung
Nguyen Thi Huong Giang
Kim Van Van
Truong Dinh Hoai
First insights into Weissella tructae infections in rainbow trout (Oncorhynchus mykiss) in Vietnam: Bacterial characterization, pathogenicity and antimicrobial susceptibility
Aquaculture Reports
Weissella tructae
Pathogenicity
Antimicrobial susceptibility
Rainbow trout
Vietnam
title First insights into Weissella tructae infections in rainbow trout (Oncorhynchus mykiss) in Vietnam: Bacterial characterization, pathogenicity and antimicrobial susceptibility
title_full First insights into Weissella tructae infections in rainbow trout (Oncorhynchus mykiss) in Vietnam: Bacterial characterization, pathogenicity and antimicrobial susceptibility
title_fullStr First insights into Weissella tructae infections in rainbow trout (Oncorhynchus mykiss) in Vietnam: Bacterial characterization, pathogenicity and antimicrobial susceptibility
title_full_unstemmed First insights into Weissella tructae infections in rainbow trout (Oncorhynchus mykiss) in Vietnam: Bacterial characterization, pathogenicity and antimicrobial susceptibility
title_short First insights into Weissella tructae infections in rainbow trout (Oncorhynchus mykiss) in Vietnam: Bacterial characterization, pathogenicity and antimicrobial susceptibility
title_sort first insights into weissella tructae infections in rainbow trout oncorhynchus mykiss in vietnam bacterial characterization pathogenicity and antimicrobial susceptibility
topic Weissella tructae
Pathogenicity
Antimicrobial susceptibility
Rainbow trout
Vietnam
url http://www.sciencedirect.com/science/article/pii/S2352513425003412
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