Study of therapeutic effectiveness, clinical and ecotoxicological safety of phosphymicine, in the treatment of aeromonosis and streptococosis in tilapia (Oreochromis niloticus)

Author(s)

Roberto Barbuio

• Document type: Doctoral Thesis
• Press: Jaboticabal. 2017-03-24.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2017-02-03
• Advisor: Marco Antonio de Andrade Belo; Claudinei da Cruz

Abstract

The present study aimed to evaluate the therapeutic efficacy of clinical and ecotoxicological safety of antimicrobial fosfomycin for the treatment of aeromonose and streptococcosis in Nile tilapia (Oreochromis niloticus). For this, clinical safety was evaluated with doses of 10, 20 and 40 mg of fosfomycin.kg-1; Efficacy studies with the therapeutic dose of 10 mg of fosfomycin.kg-1 were conducted with fish challenged with Aeromonas hydrophila and Streptococcus agalactiae; The ecotoxicity assays were performed for the determination of LC50 in fish (O. niloticus) and aquatic plants (Lemna minor) and EC50 for crustaceans (Daphnia magna) and molluscs (Pomacea canaliculata). In the studies, tilapia of 112 g ± 5.6 g were used, packed in 400 L tanks (n = 10). Both therapeutic efficacy studies with 10 mg.kg-1 demonstrated efficacy for A. hydrophila and S. agalactiae, because in the reisolation analyzes of these microorganisms there was no growth in liver, kidney, spleen and brain samples of treated fish , While in the infected and untreated groups, mean growth was greater than ten colony forming units (CFU) per plaque. In the A. hydrophila infection they presented microcytosis and lymphopenia, as well as thrombocytosis in the initial phase of infection followed by thrombocytopenia. Liver and renal tissue damage corroborated the changes in serum enzyme activity of ALT, AST, FA and creatinine, cholesterol and triglyceride levels. In S. agalactiae infection, there was a decrease in the number of erythrocytes and percentage values of hematocrit, characterizing hemolysis, associated with lymphopenia, thrombocytopenia and neutrophilia in the initial phase of infection. There was a correlation between hepatic and renal tissue damage in serum ALT, AST, AF, and creatinine levels. In the ecotoxicological assays for fish (O. niloticus), mollusc (P. canaliculata), microcrustaceans (D. magna) and macrophytes (L. minor and A. caroliniana), the results demonstrated ecotoxicological safety of fosfomycin being considered practically non-toxic for these Organisms (CL and EC 50> 100.0 mg.L-1). The Fosfomicin C® formulation attenuated pathological changes in infected fish compared to uninfected fish. However, the same formulation caused changes in the clinical safety study. The studies demonstrate the feasibility of using fosfomycin at a dose of 10 mg.kg-1 for streptococcal and aeromonose control in tilapicultura, but there is a need to test the pure antibiotic to verify if the observed changes were caused by the antibiotic or some other component. (AU)

• FAPESP's process: 13/11675-9 - Therapeutic efficacy study, clinical and ecotoxicological safety of the Fosfomicine antibiotic, administered by oral, for Aeromonas hydrophila and Streptococcus agalactiae treatment in Nile Tilapia, Oreochromis niloticus
• Grantee: Roberto Barbuio
• Support Opportunities: Scholarships in Brazil - Doctorate