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

Dis Aquat Organ. 2014 May 13;109(2):127-37. doi: 10.3354/dao02733.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aeromonas / classification*
  • Aeromonas / drug effects*
  • Animals
  • Anti-Bacterial Agents / pharmacology*
  • DNA Fingerprinting
  • DNA, Bacterial / genetics
  • DNA, Ribosomal / genetics
  • Drug Resistance, Bacterial*
  • Fish Diseases / microbiology
  • Fishes
  • Fresh Water
  • Gram-Negative Bacterial Infections / microbiology
  • Gram-Negative Bacterial Infections / veterinary*
  • Phylogeny
  • Phylogeography
  • Polymerase Chain Reaction
  • Polymorphism, Restriction Fragment Length
  • RNA, Ribosomal, 16S / genetics
  • Sepsis / microbiology
  • Sepsis / veterinary*

Substances

  • Anti-Bacterial Agents
  • DNA, Bacterial
  • DNA, Ribosomal
  • RNA, Ribosomal, 16S