Characterization and virulence potential of phenotypically diverse Aeromonas veronii isolates recovered from moribund freshwater ornamental fishes of Kerala, India
Characterization and virulence potential of phenotypically diverse Aeromonas veronii isolates recovered from moribund freshwater ornamental fishes of Kerala, India
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DOI：
10.1007/s10482-012-9786-z
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
K. Sreedharan;R. Philip;I. Singh
中科院分区：
文献类型：
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作者：
K. Sreedharan;R. Philip;I. Singh
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In the present study, we investigated the involvement ofAeromonasspp. in eliciting disease outbreaks in freshwater ornamental fishes across the state of Kerala, India. We investigated three incidences of disease, in which the moribund fishes exhibited clinical signs such as haemorrhagic septicemia (in gouramy,Trichogastersp.), dropsy (in Oscar,Astronotus ocellatus) and tail rot/fin rot (in gold fish,Carassius carassius). Pure cultures (n= 20 from each fish; 60 in total) ofAeromonasspp. were recovered from the abdominal fluid as well as from internal organs of affected fishes, although they could not be identified to species level because of the variations in their phenotypic characters. The molecular fingerprinting of the isolates using Enterobacterial Repetitive Intergenic Consensus PCR proved the genetic diversity of the isolates from the three sites. The phylogenetic trees constructed using concatenated sequences (using 16S rRNA,gyrA,gyrBandrpoDgenes) indicated that they were related toAeromonas veronii.They exhibited marked cytotoxic and haemolytic activity, which were responsible for the pathogenic potential of the isolates. The isolates possessed multiple virulence genes such as enterotoxins (actandalt), haemolytic toxins (aerAandhlyA), genes involved in type III secretion system (ascV,aexTandascF–ascG), glycerophospholipid-cholesterol acyltransferase (gcat) and a type IV pilus (tapA) gene, as determined by PCR. Virulence of representative isolates to goldfish was also tested, and we found LD50values of 104.07–105.35cfu/fish. Furthermore, the organisms could be recovered as pure cultures from the lesions as well as from the internal organs.