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15 pages, 2302 KiB

Open AccessArticle

Evaluation of a Florfenicol Formulation for Treating Streptococcosis and Francisellosis in Nile Tilapia (Oreochromis niloticus): A Study of Safety, Withdrawal Period and Efficacy

by Natália Amoroso Ferrari, Raffaella Menegheti Mainardi, Mayza Brandão da Silva, Gabriel Diogo Guimarães, Marcos Letaif Gaeta, Francisco Eduardo Pereira Rocha, Tainara Oliveira da Silva, Alene Santos Souza, Bruna Cordeiro Baptista, João Anderson Keiti Rocha, Erika Fernandes Lopes Maturana, Daniela Dib Gonçalves, Nelson Maurício Lopera Barrero, Giovana Wingeter Di Santis and Ulisses de Pádua Pereira

Microorganisms 2025, 13(3), 558; https://doi.org/10.3390/microorganisms13030558 - 1 Mar 2025

Cited by 1 | Viewed by 1040

Abstract

This study evaluates the efficacy of a new florfenicol-based drug, both in vitro and in vivo, in Nile tilapia (Oreochromis niloticus) against pathogens commonly found in fish farming and its withdrawal period. The drug’s efficacy was tested using prophylactic, metaphylactic, and therapeutic approaches against Streptococcus agalactiae (serotypes Ib and III) and Francisella orientalis. The minimum inhibitory concentration of florfenicol was 4, 5, and 128 μg/mL for the different pathogens. Fish mortality was lower in the prophylactic treatment compared to the metaphylactic and therapeutic treatments for S. agalactiae. No difference in mortality was observed for F. orientalis across treatments. Mild to moderate lesions suggestive of intoxication were observed, mainly in the liver of fish treated with overdoses or exposed to low temperatures. Florfenicol reduced mortality rates, especially with early treatment (metaphylactic), in fish experimentally challenged with the pathogens. Moreover, prophylactic antimicrobial use is not recommended, as it promotes the selection of multidrug-resistant bacterial strains. Additionally, the residual concentration of the drug in muscle tissue lasted for a shorter period than that recommended by the manufacturer, and at lower concentrations than required by national and international legislation. Full article

(This article belongs to the Special Issue Research on Diseases of Aquatic Organisms)

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13 pages, 63647 KiB

Open AccessArticle

Susceptibility of Tambaqui (Colossoma macropomum) to Nile Tilapia-Derived Streptococcus agalactiae and Francisella orientalis

by Francisco Yan Tavares Reis, Victória Pontes Rocha, Peter Charrie Janampa-Sarmiento, Ágna Ferreira Santos, Márcia Pimenta Leibowitz, Ronald Kennedy Luz, Felipe Pierezan, Sílvia Umeda Gallani, Guilherme Campos Tavares and Henrique César Pereira Figueiredo

Microorganisms 2024, 12(12), 2440; https://doi.org/10.3390/microorganisms12122440 - 27 Nov 2024

Cited by 1 | Viewed by 1298

Abstract

Nile tilapia (Oreochromis niloticus) and tambaqui (Colossoma macropomum) are the two most produced freshwater fishes in Brazil. This study investigated the potential pathogenicity of Streptococcus agalactiae and Francisella orientalis, previously isolated from diseased Nile tilapia, to tambaqui. Experimental infection trials were conducted in juvenile tambaqui at a dose of approximately 10⁷ CFU fish⁻¹, assessing clinical signs, mortality, bacterial recovery, and histopathological changes. Results demonstrated that S. agalactiae exhibited high pathogenicity to tambaqui, causing rapid disease progression, high mortality (83.33%) within 48 h post-infection, and severe lesions in multiple organs, under the experimental conditions. In contrast, F. orientalis infection did not result in mortality or clinical signs, despite bacterial recovery and granulomatous inflammation observed in the tissues. This study highlights the need to consider the potential impact of these pathogens in tambaqui farming. Full article

(This article belongs to the Special Issue Pathogens and Aquaculture)

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16 pages, 3064 KiB

Open AccessArticle

Effect of a Monoglyceride Blend in Nile Tilapia Growth Performance, Immunity, Gut Microbiota, and Resistance to Challenge against Streptoccocosis and Francisellosis

by Natália Amoroso Ferrari, Raffaella Menegheti Mainardi, Mayza Brandão da Silva, Gabriel Diogo Guimarães, João Vitor Godoy Takashe, Admilton Gonçalves de Oliveira Junior, Ricardo Mitsuo Hayashi, Giovana Wingeter Di Santis and Ulisses de Pádua Pereira

Fishes 2024, 9(9), 351; https://doi.org/10.3390/fishes9090351 - 6 Sep 2024

Viewed by 1215

Abstract

This study evaluated the effects of supplementing the diet of juvenile Nile tilapia (Oreochromis niloticus), which weighs approximately 20 g, with a blend of monoglycerides (glycerides linked to a fatty acid molecule) for 20 days during a pre-experimental challenge via the intraperitoneal route (IP). Growth performance, immunological parameters, intestinal microbiota, tissue damage, and resistance against the pathogens Streptococcus agalactiae serotypes Ib and III and Francisella orientalis were evaluated. The experimental design included a negative control (NC), a product control (NPC), a positive control for each pathogen (PC), and three groups treated with different doses (0.15, 0.25, and 0.5%). After the challenge, mortality was significantly lower in the groups treated and challenged with S. agalactiae. The treated groups showed better weight gain and food conversion rates. Innate immunity parameters showed no differences between treatments, and there was no good stimulation of diversity in the intestinal microbiota. However, in treated groups, there was a reduction in opportunistic bacteria that could cause secondary infections and increased the presence of beneficial bacteria in the intestinal tract. In this way, it is possible to validate the beneficial effects of monoglycerides as a nutritional additive for tilapia farms against streptoccocosis. Full article

(This article belongs to the Special Issue Fish Diseases Diagnostics and Prevention in Aquaculture)

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10 pages, 5381 KiB

Open AccessArticle

Pathological Manifestations of Francisella orientalis in the Green Texas Cichlid (Herichthys cyanoguttatus)

by Chia-Hsuan Chang, Sayuj Poudyal, Theeraporn Pulpipat, Pei-Chi Wang and Shih-Chu Chen

Animals 2021, 11(8), 2284; https://doi.org/10.3390/ani11082284 - 3 Aug 2021

Cited by 8 | Viewed by 4037

Abstract

Francisella orientalis (Fo) is considered to be one of the major pathogens of tilapia because of the high mortalities observed during outbreaks. Other cichlids belonging to the same family (Cichlidae) as tilapia are also quite susceptible to this pathogen. On various occasions, Fo has also been isolated from other warm water fish, including three-line grunt, hybrid striped bass, French grunt, Caesar grunt, and Indo-Pacific reef fish. However, only a few studies have reported the pathogenicity of Francisella orientalis in ornamental cichlid fish. This study fulfills Koch’s postulates by showing that a strain of Fo obtained from green Texas cichlid (Herichthys cyanoguttatus) was able to produce the same pathogenicity in healthy fish. A mortality of 100% was observed after healthy green Texas cichlid were experimentally injected with Fo at a dose of 8.95 × 10⁵ CFU/fish. DNA extracted from the organs of predilection (spleen, head kidney) gave positive results by PCR for all fish that died during the experimental period. Spleen and head kidney presented with multifocal white nodules in the affected fish, corresponding to typical vacuolated granulomas on histopathological examination of the tissues. Based on the results of this study, it is evident that Fo can indeed infect green Texas cichlid and produce a disease typical of francisellosis. Full article

(This article belongs to the Section Aquatic Animals)

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19 pages, 2215 KiB

Open AccessArticle

The Use of Extracellular Membrane Vesicles for Immunization against Francisellosis in Nile Tilapia (Oreochromis niloticus) and Atlantic Cod (Gadus morhua L.)

by Verena Mertes, Alexander Kashulin Bekkelund, Leidy Lagos, Elia Ciani, Duncan Colquhoun, Hanne Haslene-Hox, Håvard Sletta, Henning Sørum and Hanne Cecilie Winther-Larsen

Vaccines 2021, 9(1), 34; https://doi.org/10.3390/vaccines9010034 - 9 Jan 2021

Cited by 13 | Viewed by 4431

Abstract

Francisellosis in fish is caused by the facultative intracellular Gram-negative bacterial pathogens Francisella noatunensis ssp. noatunensis and Francisella orientalis. The disease is affecting both farmed and wild fish worldwide and no commercial vaccines are currently available. In this study, we tested isolated membrane vesicles (MVs) as possible vaccine candidates based on previous trials in zebrafish (Danio rerio) indicating promising vaccine efficacy. Here, the MV vaccine-candidates were tested in their natural hosts, Atlantic cod (Gadus morhua L.) and Nile tilapia (Oreochromis niloticus). Injection of MVs did not display any toxicity or other negative influence on the fish and gene expression analysis indicated an influence on the host immune response. However, unlike in other tested fish species, a protective immunity following vaccine application and immunization period could not be detected in the Atlantic cod or tilapia. Further in vivo studies are required to achieve a better understanding of the development of immunological memory in different fish species. Full article

(This article belongs to the Special Issue Vaccines for Aquaculture)

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