Morphological and biochemical characterization of two fish pathogenic bacteria: Aeromonas salmonicida and Yersinia ruckeri for rapid diagnosis of fish disease

Tasmina Akter

doi:10.3329/ajmbr.v3i1.32035

Abstract

Aeromonas salmonicida and Yersinia ruckeri are two common pathogenic fish bacteria responsible for furunculosis and Enteric Red Mouth disease (ERM), respectively. For the characterization of these two pathogens, a series of morphological (pigmentation, hemolyse, motility and body shape), biochemical tests (Gram staining, catalase, oxidase and API 20E strips) and a soft ionization technique (MALDI-TOF/MS) were performed in the laboratory. Pigmentation, motility, hemolysis and body shape was used as a preliminary identification of the bacteria. Both of the species were identified with the entire biochemical test without any doubt except API20E strips test. Although the API profile of A. salmonicida (0006104) was identified with high confidence (99.6%), but Y. ruckeri was misidentified as Vibrio mimicus. There are strong supports against Vibrio mimicus as it is a human pathogen, grow at a temperature more than 20oC, motile and oxidase positive bacteria. The Y. ruckeri is a non-motile fish bacteria and oxidase negative which are consistent with the study results. Agglutination test with Bionor Mono kit was also identified the bacteria as Y. ruckeri. For rapid diagnosis of infectious disease, accurate identification of pathogen is very important for commercial aquaculture.Asian J. Med. Biol. Res. March 2017, 3(1): 44-51

Highlights

Fish diseases have been identified one of the major problem in aquaculture industry, where outbreaks begin either suddenly or progress rapidly often with high mortalities
Analytical Profile Index (API) 20E strips (Biomerieux), agglutination (BioNor Mono Yr) and MALDI-TOF/mass spectrometry (MS) test were performed for the confirmation of the experimental bacteria
The results suggest that the proteometric based MALDI-TOF MS-based identification represents a powerful device for quick and correct classification and characterization of A. salmonicida and Y. ruckeri species

Summary

Introduction

Fish diseases have been identified one of the major problem in aquaculture industry, where outbreaks begin either suddenly or progress rapidly often with high mortalities. Aeromonas salmonicida and Yersinia ruckeri are two fish pathogenic bacteria responsible for furunculosis and yersiniosis or enteric red mouth (ERM) disease, respectively Both of the bacteria are responsible for causing disease in freshwater and marine water fishes worldwide (Welch et al, 2011). A. salmonicida was isolated from a hatchery of brown trout (Salmo trutta) in Germany (Austin, 2011) and Y. ruckeri was from rainbow trout (Oncorhynchus mykiss) in the Hagerman Valley, Idaho, USA (Ross et al, 1966) These bacterial species are significant pathogens of cultivated salmonids in both fresh and marine water farms (Austin & Austin, 2007).

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