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Antonie van Leeuwenhoek

, Volume 103, Issue 1, pp 53–67 | Cite as

Characterization and virulence potential of phenotypically diverse Aeromonas veronii isolates recovered from moribund freshwater ornamental fishes of Kerala, India

  • Krishnan Sreedharan
  • Rosamma Philip
  • Isaac Sarojani Bright Singh
Original Paper

Abstract

In the present study, we investigated the involvement of Aeromonas spp. 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, Trichogaster sp.), 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) of Aeromonas spp. 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, gyrB and rpoD genes) indicated that they were related to Aeromonas 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 (act and alt), haemolytic toxins (aerA and hlyA), genes involved in type III secretion system (ascV, aexT and ascFascG), 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 LD50 values of 104.07–105.35 cfu/fish. Furthermore, the organisms could be recovered as pure cultures from the lesions as well as from the internal organs.

Keywords

Aeromonas veronii Ornamental fishes Phenotypic diversity Virulence potential 

Notes

Acknowledgments

The authors acknowledge The Marine Products Export Development Authority (MPEDA), Ministry of Commerce & Industry, Govt. of India (Project code: 3/3/OFD/HO/2003 dated 25-02-2004), and Department of Biotechnology (DBT), Govt. of India (Project Code: BT/PR4012/AAQ/03/204/2003), for financial support. The first author thanks MPEDA for Fellowship.

Supplementary material

10482_2012_9786_MOESM1_ESM.doc (5 mb)
Supplementary material 1 (DOC 5101 kb)

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Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • Krishnan Sreedharan
    • 1
  • Rosamma Philip
    • 2
  • Isaac Sarojani Bright Singh
    • 1
  1. 1.National Centre for Aquatic Animal HealthCochin University of Science and TechnologyCochinIndia
  2. 2.Department of Marine Biology, Microbiology and Biochemistry, School of Marine SciencesCochin University of Science and TechnologyCochinIndia

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