期刊
PATHOGENS
卷 12, 期 4, 页码 -出版社
MDPI
DOI: 10.3390/pathogens12040598
关键词
mortality; 16S rRNA gene; virulence gene; immunity
类别
This study investigated a case of severe mortality in farmed Labeo rohita and identified the causative agent as Aeromonas veronii. The isolated strain showed resistance to ampicillin and dicloxacillin, but susceptibility to 22 other antibiotics. It was also found that A. veronii induced stress and immune responses in L. rohita. The negative effects of the pathogen on fish health and high mortality rate highlight the need for A. veronii management.
A case of severe mortality in farmed Labeo rohita was investigated to characterize the causative agent. We identified the bacterial strain as Aeromonas veronii isolated from the gut of infected L. rohita by biochemical assay, scanning electron microscopy and 16S rRNA gene sequence analysis. The in vivo challenge experiment showed that the LD50 of A. veronii was 2.2 x 10(4) CFU/fish. Virulence gene investigation revealed that the isolated A. veronii possesses Aerolysin, Cytotoxic enterotoxin, Serine protease, Dnase and Type III secretion system genes. The isolated strain was resistant to two antibiotics (ampicillin and dicloxacillin) while susceptible to 22 other antibiotics. The study further revealed that A. veronii induced both stresses along with non-specific and specific immune responses marked by elevated cortisol HSP70, HSP90 and IgM levels in the treated L. rohita fingerlings. Although the bacterial pathogen enhances the immune response, the negative effect on fish, including stress, and high mortality, create concern and a need for A. veronii management in L. rohita farms. The knowledge gained from this study would facilitate future research aimed at assessing the pathogenicity of A. veronii, with an emphasis on microbial disease management in other farmed fish species.
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