Comparative Pathogenicity of <i>Aeromonas</i> spp. in Cultured Red Hybrid Tilapia (<i>Oreochromis niloticus × O. mossambicus</i>)
The genus <i>Aeromonas</i> has been recognised as an important pathogenic species in aquaculture that causes motile <i>Aeromonas</i> septicaemia (MAS) or less severe, chronic infections. This study compares the pathogenicity of the different <i>Aeromonas</i> spp....
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| Autores principales: | , , , , , , , , , , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/1225e12b725148a58d05d838cf480da6 |
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| Sumario: | The genus <i>Aeromonas</i> has been recognised as an important pathogenic species in aquaculture that causes motile <i>Aeromonas</i> septicaemia (MAS) or less severe, chronic infections. This study compares the pathogenicity of the different <i>Aeromonas</i> spp. that were previously isolated from freshwater fish with signs of MAS. A total of 124 isolates of <i>Aeromonas</i> spp. were initially screened for the ability to grow on M9 agar with <i>myo</i>-inositol as a sole carbon source, which is a discriminatory phenotype for the hypervirulent <i>A. hydrophila</i> (vAh) pathotype. Subsequently, LD<sub>50</sub> of six selected <i>Aeromonas</i> spp<sub>.</sub> were determined by intraperitoneal injection of bacterial suspension containing 10<sup>3</sup>, 10<sup>5</sup>, and 10<sup>7</sup> CFU/mL of the respective <i>Aeromonas</i> sp. to red hybrid tilapias. The kidneys, livers and spleens of infected moribund fish were examined for histopathological changes. The screening revealed that only <i>A. dhakensis</i> 1P11S3 was able to grow using <i>myo</i>-inositol as a sole carbon source, and no vAh strains were identified. The LD<sub>50–240h</sub> of <i>A. dhakensis</i> 1P11S3 was 10<sup>7</sup> CFU/mL, while the non-<i>myo</i>-inositol utilizing <i>A. dhakensis</i> 4PS2 and <i>A. hydrophila</i> 8TK3 was lower at 10<sup>5</sup> CFU/mL. Similarly, tilapia challenged with the <i>myo</i>-inositol <i>A. dhakensis</i> 1P11S3 showed significantly (<i>p</i> < 0.05) less severe signs, gross and histopathological lesions, and a lower mortality rate than the non-<i>myo</i>-inositol <i>A. dhakensis</i> 4PS2 and <i>A. hydrophila</i> 8TK3. These findings suggested that <i>myo</i>-inositol utilizing <i>A. dhakensis</i> 1P11S3 was not a hypervirulent <i>Aeromonas</i> sp. under current experimental disease challenge conditions, and that diverse <i>Aeromonas</i> spp. are of concern in aquaculture farmed freshwater fish. Therefore, future study is warranted on genomic level to further elucidate the influence of <i>myo</i>-inositol utilizing ability on the pathogenesis of <i>Aeromonas</i> spp., since this ability correlates with hypervirulence in <i>A. hydrophila</i> strains. |
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