J Vet Sci.  2016 Sep;17(3):377-383. 10.4142/jvs.2016.17.3.377.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry based identification of Edwardsiella ictaluri isolated from Vietnamese striped catfish (Pangasius hypothalamus)

Affiliations
  • 1Laboratory of Aquatic Animal Diseases, Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea. jungts@gnu.ac.kr
  • 2Haeyeon Fish Farm, Jeju 63359, Korea.
  • 3BluGen Korea, Busan 48071, Korea.

Abstract

Edwardsiella (E.) ictaluri is a major bacterial pathogen that affects commercially farmed striped catfish (Pangasius hypothalamus) in Vietnam. In a previous study, 19 strains of E. ictaluri collected from striped catfish were biochemically identified with an API-20E system. Here, the same 19 strains were used to assess the ability of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS; applied using a MALDI Biotyper) to conduct rapid, easy and accurate identification of E. ictaluri. MALDI-TOF MS could directly detect the specific peptide patterns of cultured E. ictaluri colonies with high (> 2.0, indicating species-level identification) scores. MALDI Biotyper 3.0 software revealed that all of the strains examined in this study possessed highly similar peptide peak patterns. In addition, electrophoresis (SDS-PAGE) and subsequent immuno-blotting using a specific chicken antibody (IgY) against E. ictaluri revealed that the isolates had highly similar protein profiles and antigenic banding profiles. The results of this study suggest that E. ictaluri isolated from striped catfish in Vietnam have homologous protein compositions. This is important, because it indicates that MALDI-TOF MS analysis could potentially outperform the conventional methods of identifying E. ictaluri.

Keyword

Edwardsiella ictaluri; MALDI Biotyper; Pangasius hypothalamus; identification method

MeSH Terms

Animals
*Catfishes
Edwardsiella ictaluri/classification/*isolation & purification
Enterobacteriaceae Infections/diagnosis/microbiology/*veterinary
Fish Diseases/diagnosis/*microbiology
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/*veterinary
Vietnam

Figure

  • Fig. 1 Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) spectral profiles of three representative Edwardsiella (E.) ictaluri strains, as generated using the flex Analysis software and a MALDI Biotyper system. The relative intensities of the ions are shown on the Y-axis, and the ion masses (in Daltons) are shown on the X-axis. The m/z value gives the mass-to-charge ratio. Peptide peaks common to all strains are indicated with arrow heads above the panel, and the peaks with black lines in the panel represent different peaks between the four strains. a.u., arbitrary units.

  • Fig. 2 Electrophoresis (SDS-PAGE) (A) and Western blot (B) analysis of whole cell lysates from E. ictaluri isolated from striped catfish. Black arrows indicate consistent bands of whole cell lysates.


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