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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Nile tilapia (Oreochromis niloticus) challenged infection by Francisella noatunensis subsp. orientalis via an intragastric route protocol

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Fernandez-Alarcon, M. F. [1] ; Santana, A. M. [2] ; Viadanna, P. H. O. [3] ; Manzini, B. [2] ; Natori, M. M. [1] ; Ishikawa, C. M. [1] ; Dias, D. C. [1] ; Ranzani-Paiva, M. J. T. [1] ; Squassoni, G. H. [4] ; Couto, F. D. [2] ; Furlan, L. R. [5] ; Tachibana, L. [1]
Total Authors: 12
[1] Fishery Inst APTA SAA, Res Ctr Aquaculture, Av Francisco Matarazzo 455, BR-05001900 Sao Paulo, SP - Brazil
[2] PREVET Sanidade Aquicola, Av Olga Morello de Stefani 260, BR-14887364 Jaboticabal, SP - Brazil
[3] UNIPAC Fac Antonio Carlos Uberlandia, Ave Cipriano Del Favero 991, BR-38400106 Uberlandia, MG - Brazil
[4] Fed Univ Sao Carlos UFSCar, Ctr Agr Sci, Rodovia Anhanguera, Km 174, BR-13604900 Araras, SP - Brazil
[5] Sao Paulo State Univ, UNESP, Aquaculture Ctr, Via Acesso Prof Paulo Donato Castellane S-N, BR-14884900 Sao Paulo - Brazil
Total Affiliations: 5
Document type: Journal article
Source: Aquaculture; v. 510, p. 380-385, AUG 15 2019.
Web of Science Citations: 0

Francisella noatunensis subsp. orientalis (Fno) is an emerging bacterial pathogen that causes acute or chronic disease in tilapia (Oreochromis sp). Previous studies have established experimental models of Fno infection via intraperitoneal and immersion route. However, there have been no reports of Fno challenge through the gastrointestinal mucosa. In this study, we aimed to determine the median lethal dose (LD50) of Fno by intragastric infection, evaluating the clinical signs, mortality, anatomopathological findings, and recovery of pathogenic bacteria from infected organs of infected tilapia. A total of 200 tilapias, weighing approximately 20 g each, were equally distributed in 20 aquariums, containing 50 L of water maintained at 23 degrees C; five different randomized treatments, were applied to them. Tilapias were either inoculated (via an intragastric injection) with 300 mu L of saline solution (CON) or bacterial solution containing 3.99 x 10(6) CFU (INF 10(6)), 3.99 x 10(5) CFU (INF 10(5)), 3.99 x 10(4) CFU (INF 10(4)) and 3.99 x 10(3) CFU (INF 10(3)) of Fno. Tilapias were monitored for up to 15 days postinfection (dpi) and mortality rates recorded to calculate the LD50. At 15 dpi, necropsies and microbiological analyses were performed in the surviving fish from all groups. In addition, histopathological evaluations (spleen, gill, intestine, liver, kidney, and brain) and Fno confirmation assays were performed in CON and INF 10(5) (mortality closer to LD50) inoculated tilapias. While no mortality was observed in CON, mortality rates ranged from 42.5 to 80.0% in the Fno inoculated groups. Both microbiological and PCR analyses confirmed the presence of Fno in the internal tissues (kidneys and spleen) of the INF 10(5) group. Fno challenged groups showed macroscopic lesions in several tissues, which were consistent with the pathological features of francisellosis. Additionally, INF 10(5) group had microscopic lesions suggestive of the disease. This study determined the LD50 of Fno by the intragastric infection methodology, after 15 dpi, at 6.32 x 10(4) CFU. We report for the first time that Fno inoculated through the intragastric route, can reach the internal organs of tilapia, causing lesions in spleen, liver, and kidneys. This finding is important to test the efficacy of substances targeting the intestinal mucosa, such as prebiotics, probiotics, and organic acids. Moreover, the intragastric challenge for Fno presented here may be useful to improve the comprehension of the physiopathology of the disease. (AU)

FAPESP's process: 16/25347-1 - Development of a attenuated vaccine for control and prevention of infections caused by Francisella noatunensis subspecies orientalis in fish farms
Grantee:Miguel Frederico Fernandez Alarcon
Support type: Research Grants - Innovative Research in Small Business - PIPE
FAPESP's process: 17/23269-6 - Development of an attenuated vaccine for control and prevention of infections caused by Francisella noatunensis subspecies Orientalis in Fish Farms
Grantee:Miguel Frederico Fernandez Alarcon
Support type: Scholarships in Brazil - Innovative Research in Small Business - PIPE
FAPESP's process: 17/24653-4 - Production of three mutant strains of Francisella noatunensis orientalis by deletion of the virulence genes igl and pdp
Grantee:Fabrício David Couto
Support type: Scholarships in Brazil - Technical Training Program - Technical Training