Influence of medium composition on the growth, morphology, and virulence of Flavobacterium columnare in Piaractus mesopotamicus

• Grant number: 17/19495-0
• Support type: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): December 01, 2017
• Effective date (End): November 30, 2018
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Pathology
• Principal researcher: Julieta Rodini Engracia de Moraes
• Grantee: Livia Saccani Hervas
• Home Institution: Centro de Aquicultura (CAUNESP). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil

Abstract

Flavobacterium columnare is one of the main pathogens in freshwater fish farms. Preliminary tests in our laboratory showed a putative association between morphology, growth medium and virulence of a local isolate of F. columnare, however were not considered several mediums reported by the literature and the association was not fully clarified. The aim of this proposal is to evaluate the growth, morphological variations and virulence of a F. columnare isolate. The project will be subdivided into two experiments. First, the growth of an inoculum of F. columnare will be tested in 8 different broths (Cytophaga, TYES, Hsu & Shoots, Shieh, FCGM, G1-b, G2-b and G3-b), by measuring the optical density (OD600nm), and the morphological characteristics according to visual scale of filament formation 24, 48, 72 and 96h after streaking. The best five culture media (better growth and less filament formation) will be used for bacterial challenge and assessment of in vitro adherence. For this, 180 juveniles of Piaractus mesopotamicus (50g) will be distributed in six experimental groups, in triplicate. One group will be used as control (PBS injection) and five treatments inoculated with an standardized dose of F. columnare for all broths. Clinical signs and mortality will be assessed for 14 days. Fragments of head kidney, spleen, liver, pyloric cecum, gut and gills will be collected from surviving animals for histopathology. In vitro adherence capacity will be determined from samples of the infective inoculum. The study hopes to contribute to the knowledge of the virulence mechanisms of F. columnare and to define the best culture medium for bacterial challenges. (AU)