Flavobacterium columnare pathogenesis and pacu resistance (Piaractus mesopotamicus) to bacteria

• Grant number: 18/24499-8
• Support type: Scholarships in Brazil - Post-Doctorate
• Effective date (Start): July 01, 2019
• Effective date (End): March 09, 2020
• Field of knowledge: Agronomical Sciences - Fishery Resources and Fishery Engineering - Aquaculture
• Principal researcher: Fabiana Pilarski
• Grantee: Geovana Dotta Tamashiro
• Home Institution: Centro de Aquicultura (CAUNESP). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil

Abstract

The bacterium Flavobacterium columnare has a substantial impact on fish farming, being considered one of the greatest obstacles to the development of this activity worldwide, due to its virulence potential and high cost of treatment, which often becomes impracticable. The knowledge of the pathogenesis of F. columnare in Piaractus mesopotamicus is limited, being this one of the native fish species most used in intensive breeding in Brazil. Therefore, the description of how the bacteriose attacks the animal organism and how the natural defense system reacts, becomes necessary for the development of alternative treatment and prevention of colonization. Thus, this study will describe the pathogenesis, emphasizing the mechanisms of the innate immune system. Infection will be evaluated at 0, 6h, 24h, 7 days and 14 days after intracellular inoculation of the bacterium, ranging from absence of infection to infection in acute to chronic phases for analysis of gene expression (IRAK-1, IL-6, IL-10 and IL-1b), complement system proteins (C3 and C4) and lysozyme. In addition, the histopathological, hematological, biochemical and immunological characterization of infected animals will be performed in the same phases of infection. As an alternative to prevent this disease, this work will also evaluate the use of the macroalga Ulva lactuca as an immunostimulating ingredient in the diet of P. mesopotamicus experimentally infected with F. columnare. Diets supplemented with the study extract administered to pacu juveniles for 15 days will be formulated for subsequent evaluation of the following immunological parameters: genetic expression of interleukins, serum lysozyme levels, inflammatory response, phagocytic activity and survival after challenge with the bacteria alive. This study is expected to reveal the multiple mechanisms of P. mesopotamicus for signaling and control of infection caused by F. columnare. In addition, provide subsidies for the substitution of the use of antimicrobials and chemotherapeutics in the treatment of infectious diseases, by natural ingredients in preventing the manifestation of columnaris. (AU)