First isolation of Chryseobacterium sp. as a pathogen of fish eggs
In recent years, disease has become a major limiting factor in the development of the tilapia fry culture industry. This study isolated eight dominant bacterial strains, designated A8PD1 to A8PD8, from diseased Nile tilapia (Oreochromis niloticus) eggs. Among them, strain A8PD8 exhibited the highest...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2025-09-01
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| Series: | Aquaculture Reports |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2352513425003783 |
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| Summary: | In recent years, disease has become a major limiting factor in the development of the tilapia fry culture industry. This study isolated eight dominant bacterial strains, designated A8PD1 to A8PD8, from diseased Nile tilapia (Oreochromis niloticus) eggs. Among them, strain A8PD8 exhibited the highest pathogenicity, causing up to 70 % egg mortality and deformities in hatchlings. Infection experiments demonstrated that increasing concentrations of A8PD8 led to higher egg mortality and deformity rates, with an LD50 of 2.03 × 10⁶ CFU/mL. Pathological analysis confirmed that A8PD8 infection damaged egg membrane integrity and disrupted embryonic development. Morphological, physiological, biochemical, 16S rRNA and genome-wide analyses identified A8PD8 as a Gram-negative bacillus with closest similarity to Chryseobacterium. urinae. Antibiotic susceptibility testing showed that the bacterium was most sensitive to clindamycin (MIC=1 μg/mL) and most resistant to ceftazidime (MIC>256 μg/mL). Whole-genome sequencing revealed that the A8PD8 genome is 4,480,960 bp, with a GC content of 35.72 %, encoding 285 virulence genes and 169 resistance genes. This is the first report of a pathogenic Chryseobacterium strain affecting fish eggs, providing a scientific foundation for preventing and controlling Chryseobacterium infections during tilapia egg incubation. |
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| ISSN: | 2352-5134 |