Aeromonas bacteria can cause an infection characterized by septicemia and is one of the most common pathogens in tropical fish. This disease is responsible for high morbidity and mortality rates, causing considerable losses in aquaculture. Thus, the understanding of its pathophysiology is crucial to develop control strategies of this bacterial infection in farmed fish. This study aimed to characterize early pathological aspects of acute sepsis in pacu (Piaractus mesopotamicus) experimentally infected with Aeromonas hydrophila. A total of 160 juvenile pacus were inoculated intraperitoneally with A. hydrophila (1.78 x 109 CFU/mL) and at 0 (control), 1, 3, 6, and 9 hours post-inoculation (hpi), animals were anesthetized and samples were collected for microbiological, light microscopy and transmission electron microscopy (TEM) analyzes. The results showed the occurrence of hemodynamic alterations, such as hemorrhage and congestion, which were observed mainly after 6 and 9 hpi. It was possible to re-isolate Aeromonas at all sampling times except in control group. However, just after 9 hpi it was possible to find the bacteria in all fish and tissues. Light microscopy analyses revealed a degenerative process, necrosis and vascular damage mainly at 6 and 9 hpi. According to the ultrastructural examination, areas of cellular death were identified in all examined tissues, especially at 6 and 9 hpi. However, the most severe, related to necrosis, were observed after 6 and 9 hpi. The findings suggested that this bacterium spreads in the first hpi through the fish organs, mainly affecting spleen, liver and kidney, causing irreversible lesions at the molecular level.

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Wound healing and tissue repair are necessary to ensure survival and health of any organism. The aim of this study was to investigate the impact of supplementation with chromium carbochelate (CC) and Saccharomyces cerevisiae (SC) on wound healing in tropical teleost fish Piaractus mesopotamicus. Thus, fish were distributed into four groups: a) control (without supplementation); b) supplemented with 18 mg/kg of chromium carbochelate; c) supplemented with 0.3% of S. cerevisiae and d) supplemented with an association of both supplements. After 105 days of feeding, full-thickness skin incisions (2.0 x 1.0 x 0.25 cm) were performed removing epidermis and dermis. Macroscopic and histologic observations were carried out at 1, 3, 7, 14, 21, 28, and 35 days after wounding to monitor the healing rate. Opposing fronts advanced gradually and faster each day demonstrating a progressive increase in the healing process over time. The inflammatory process was exacerbated and expansive, with an increase in mucous cells and chromatophores. Although no significant differences were observed between groups on wound retraction and microscopic parameters, fish supplemented with CC and SC showed faster re-epithelialization, greater degree of organization of collagen fibers, and higher neovascularization. We concluded that supplementation with S. cerevisiae and chromium carbochelate improves specific aspects of cutaneous healing process in pacu. Keywords: Tissue repair. Chromium carbochelate. Saccharomyces cerevisiae. Freshwater fish. Pacu. ResumoA cicatrização e reparação de tecidos são mecanismos essenciais para garantir a sobrevivência e saúde de qualquer indivíduo. O objetivo deste trabalho foi avaliar o impacto da suplementação com carboquelato de cromo (CC) e Saccharomyces cerevisiae (SC) sobre a cicatrização no peixe tropical Piaractus mesopotamicus. Para isto, os peixes foram distribuídos em quatro grupos: controle (sem tratamento), suplementados com 18 mg/kg de carboquelato de cromo, 0,3% de S. cerevisiae e associação de ambos os suplementos. Após 105 dias de alimentação, foram realizadas incisões na pele de espessura completa (2,0 x 1,0 x 0,25 cm) removendo epiderme e derme. Avaliações macroscópicas e microscópicas foram realizadas 1, 3, 7, 14, 21, 28 e 35 dias após a indução das feridas, para monitorar a taxa de cicatrização. As bordas opostas das feridas avançaram gradualmente a cada dia, demonstrando o aumento progressivo do processo de cicatrização ao longo do tempo. O processo inflamatório foi exacerbado e expansivo, com aumento no número de células mucosas e cromatóforos. Apesar deste processo, não foram observadas diferenças significativas na retração das feridas e nos parâmetros microscópicos entre os grupos. Peixes suplementados com CC ou Sc apresentaram rápida reepitelização, maior grau de organização de fibras colágenas e de neovascularização inicial. Concluiu-se que a suplementação com S. cerevisiae ou carboquelato de cromo melhora aspectos específicos do processo cicatricial no pacu. Palavras-chave: Reparo...

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This study aimed to investigate outbreak with high mortality in cultured juvenile cobia occurred in Southeast Brazil in 2011. Fish displayed retarded growth rates, lethargy, fin ulceration, skin depigmentation, corneal opacity, and physical deformities. Internally, livers were increased in volume and pale in different degrees. Firm whitish nodules were disseminated in the liver, kidney and spleen. A moderate number of parasites identified as Neobenedenia melleni were recovered from the body surface. Microscopically, severe hepatic steatosis and extensive granulomatous lesion were identified in all fish sampled. Microbiological analysis of moribund fish revealed the presence in pure culture of a Gram-negative bacterium identified as Photobacterium damselae subsp. piscicida using biochemical and molecular characteristics. Analysis of the partial 16S rRNA sequences confirmed the results demonstrating high identity (98%). The isolates were sensitive to chloramphenicol and enrofloxacin and resistant to ciprofloxacin, florfenicol, doxycycline hydrochloride, norfloxacin, oxytetracycline, and tetracycline. Chronic pasteurellosis was considered as the main problem in the farm, while hepatic steatosis and parasitic infestation may have contributed to the development of the process.

Feeding accounts for 50%-60% of production costs in fish farming, and alternative raw materials are used to lower production costs. These raw materials can alter nutritional values and sensory aspects of the final product. The present study describes the results for the proximal composition, sensory, and microbiological analyses of red tilapia (Oreochromis sp.) fed with a biofloc meal (fish sediment residue). The results showed that the red tilapia biofloc meal contained protein levels over 30%, with 3% nitrogen and 6% calcium. Fish fed biofloc meal showed productive performances within the ranges established for the species. Sensory analysis revealed that the cooked product's appearance was very characteristic, presenting a slight metallic flavor and moderate juiciness. The bromatological composition analysis indicated that each 100g of tilapia contained 16 g of protein. Finally, the microbiological study guarantees compliance with the local tandards and confirms that the product does not contain significant levels of microorganisms that could cause foodborne diseases when consumed by humans. In conclusion, the use of biofloc meal at a small red tilapia farm proved to be a sustainable alternative for feeding Oreochromis sp.

Streptococcosis caused by Streptococcus agalactiae is a major economic problem for Nile tilapia Oreochromis niloticus production worldwide. Inactivated vaccines are considered an efficient method for controlling streptococcosis. However, during the vaccination process, stress during fish handling could affect the immune response. Immunomodulators, such as thymomodulin, act on the immune system and can improve vaccination responses. Thus, the aim of this study was to assess the immunomodulatory effect of thymomodulin in O. niloticus vaccinated against S. agalactiae. For this, fish were distributed in a factorial design (2x2x6), corresponding to two levels of thymomodulin supplementation (0.0 and 0.3%), two treatments (sterile phosphate buffered saline and inactivated S. agalactiae vaccine). Initially, fish received thymomodulin supplementation for 30 days. Next, fish were vaccinated by injection intraperitoneal (i.p.) of heat inactivated S. agalactiae vaccine. 15 days after vaccination, all fish were challenged i.p. with S. agalactiae and blood samples were collected at 7, 14, 21 days post infection (DPI). Results revealed that fish supplemented with thymomodulin vaccinated or not developed better protection against S. agalactiae than vaccinated fish without thymomodulin. Furthermore, fish vaccinated and supplemented with thymomodulin presented high levels of antibodies after 14 and 21 DPI, suggesting that thymomodulin can promote the immune response in Nile tilapia.