DAO 109:127-137 (2014)  -  DOI: https://doi.org/10.3354/dao02733

Characterization and antimicrobial susceptibility of motile aeromonads isolated from freshwater ornamental fish showing signs of septicaemia

S. S. S. de S. Jagoda1,2, T. G. Wijewardana2,4, A. Arulkanthan2, Y. Igarashi1, E. Tan1, S. Kinoshita1, S. Watabe3, S. Asakawa1,*

1Laboratory of Aquatic Molecular Biology and Biotechnology, Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
2Center for Aquatic Animal Disease Diagnosis and Research, Department of Veterinary Pathobiology, Faculty of Veterinary Medicine and Animal Science, University of Peradeniya, Peradeniya 20400, Sri Lanka
3School of Marine Biosciences, Kitasato University, Minami Ku, Sagamihara, Kanagawa 252-0373, Japan
4Present address: No. 408/35, Mount Pleasant Garden II, Bowelawatte, Kandy 20000, Sri Lanka
*Corresponding author:

ABSTRACT: A total of 74 phenotypically identified presumptive motile Aeromonas isolates recovered from septicaemic freshwater ornamental fish in Sri Lanka were genetically characterized by sequencing of rpoD and gyrB genes. rpoD/gyrB phylogeny confirmed only 53 isolates as Aeromonas, among which A. veronii was the predominant species (79.2%), followed by A. hydrophila (7.5%), A. caviae (5.7%), A. jandaei (1.9%), A. dhakensis (3.8%) and A. entero pelogenes (1.9%). The aeromonads confirmed by sequencing were further subjected to 16S rDNA PCR-RFLP which substantiated sequencing results for 83% of isolates. Fingerprinting of A. enteropelogenes (n = 42) using ERIC-PCR revealed no dominant clones, and the majority were genetically distinct. All isolates were screened by PCR for 7 virulence determinant genes (aer, act, ast, alt, fla, ser, exu) and 2 integrase encoding genes (intI1, intI2). Each isolate contained ≥3 of the virulence genes tested for, with a heterogeneous distribution. Of the isolates, 77% harboured the intI1 gene, while none had intI2. In vitro antimicrobial susceptibility testing showed highest resistances towards tetracycline (58.5%) and erythromycin (54.7%). Our results indicate the diverse range of aeromonads that could potentially be associated with motile aeromonad septicaemia in ornamental fish. This is the first isolation of A. dhakensis from a septicaemic ornamental fish since its original description from the same host.


KEY WORDS: Aeromonas veronii · Antimicrobial resistance · Motile aeromonad septicaemia · Ornamental fish · Phylogenetic identification · Virulence genes


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Cite this article as: Jagoda SSSdS, Wijewardana TG, Arulkanthan A, Igarashi Y and others (2014) Characterization and antimicrobial susceptibility of motile aeromonads isolated from freshwater ornamental fish showing signs of septicaemia. Dis Aquat Org 109:127-137. https://doi.org/10.3354/dao02733

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