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United States Department of Agriculture

Agricultural Research Service

Research Project: Integrated Aquatic Animal Health Strategies

Location: Aquatic Animal Health Research

Title: Evaluation of an in vitro cell assay to select attenuated bacterial mutants of Aeromonas hydrophila and Edwardsiella tarda to channel catfish

item Wei Pridgeon, Yuping
item Klesius, Phillip
item Mu, Xingjiang

Submitted to: Annual Meeting World Aquaculture Society
Publication Type: Proceedings
Publication Acceptance Date: 8/17/2012
Publication Date: 2/21/2013
Citation: Wei Pridgeon, Y., Klesius, P.H., Mu, X. 2013. Evaluation of an in vitro cell assay to select attenuated bacterial mutants of Aeromonas hydrophila and Edwardsiella tarda to channel catfish. Proceedings of Aquaculture 2013. p. 875.

Interpretive Summary:

Technical Abstract: Both Aeromonas hydrophila (causative agent of motile aeromonas septicemia) and Edwardsiella tarda (causative agent of enteric septicemia) are Gram-negative bacteria widely distributed in aquatic environments, affecting many fish species worldwide, including channel catfish and tilapia. To control bacterial diseases, feeding infected fish with antibiotics-medicated food is a general practice. However, currently there are only three FDA approved antibiotics for use in aquaculture: oxytetracycline, sulfadimethoxine, and aquafluor. The widespread use of the limited number of antibiotics for treating bacteria diseases in aquaculture has led to the development of antibiotic resistance in many fish pathogens, including A. hydrophila and E.tarda. Therefore, alternative control method such as the use of vaccines is urgently needed. To develop novel attenuated vaccines against bacteria such as A. hydrophila and E. tarda, large numbers of mutants are usually generated. To determine whether any of these mutants are attenuated, in vivo virulence studies using live fish are routinely performed. However, in vivo virulence studies for large number of mutants require many fish and aquariums as well as large quantity of water, which can be quite expensive. To reduce the cost involved in the in vivo virulence study using live fish, an in vitro method is urgently needed. Using catfish gill cells G1B, the feasibility of using an in vitro assay instead of in vivo virulence assay using live fish to select attenuated bacterial mutants was evaluated in this study. Pearson correlation analysis between in vitro virulence to G1B cells and in vivo virulence of Aeromonas hydrophila and Edwardsiella tarda revealed that there was a significant correlation between the two (r = - 0.768, P value = 3.7 X 10 -16) (Figure 1). This in vitro cell assay might be initially used to screen large quantities of bacteria to select attenuated mutants of catfish pathogens. The use of this in vitro cell assay using catfish gill cells to identify attenuated mutants of catfish pathogens will reduce cost associated with the in vivo fish virulence assay.

Last Modified: 10/17/2017
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