Assessment of Encapsulated Probiotic Lactococcus lactis A12 Viability Using an In Vitro Digestion Model for Tilapia.

Probiotics face harsh conditions during their transit through the gastrointestinal tract (GIT) of fish because of low-pH environments and intestine fluid. Therefore, the evaluation of probiotic viability under simulated gastrointestinal conditions is an important step to consider for probiotic supplementation in fish feed prior to in vivo trials. Therefore, this study aimed to evaluate the effect of stomach and intestinal simulated conditions on the viability of encapsulated Lactococcus lactis A12 using an in vitro digestion model for tilapia. A Box Behnken design was used to evaluate the potential effect of three factors, namely stomach pH, residence time in the stomach, and enzyme quantity, on the viability of encapsulated Lactococcus lactis A12. As the main results, low pH (4.00), long residence time (4 h), and enzyme quantity (2.68 U of total protease activity) led to lower final cell counts after the phases of the stomach and intestine. Encapsulated probiotic bacteria showed higher viability (p < 0.05) and antibacterial activity (p < 0.05) against the pathogen Streptococcus agalactiae than non-encapsulated bacteria. The results suggest that L. lactis A12 survives in GIT conditions and that the proposed in vitro model could be used to explore the viability of probiotic bacteria intended for fish feed supplementation.

Assessment of Bacillus species capacity to protect Nile tilapia from A. hydrophila infection and improve growth performance.

The present study evaluated the capacity of three Bacillus species to improve health status and growth performance of Nile Tilapia fed with high levels of soybean meal and challenged with Aeromonas hydrophila. In vitro experiments showed that ß-hemolysin and metalloprotease enzymes were produced by A. hydrophila throughout the exponential growth phase. In vivo experiments showed that 107 colony-forming units (CFUs)/ml of this pathogen killed 50% of control group fishes in 13 days. To evaluate the influence of Bacillus strains on health status and growth performance in Nile Tilapia, 180 fishes (33.44 + 0.05 g) were distributed in 12 tanks of 200 L each, and animals were fed twice per day until satiety. 1) Control group without Bacillus, 2) Bacillus sp1, 3) Bacillus sp2, and 4) Bacillus sp3 groups were formulated containing 106 CFU/g. After 40 days of feeding, the fishes were intraperitoneally injected with 1 ml of A. hydrophila at 2 × 107 CFU/ml, and mortality was recorded. The results showed that cumulative mortality rate was significantly (p< 0.05) lower in the Bacillus sp1 (25%), sp2 (5%), and sp3 (15%) groups, than the control group (50%). Weight gain was also significantly better (p< 0.05) in the Bacillus sp1 (36%), sp2 (67%), and sp3 (55%) groups with respect to the control group (30%). In conclusion, functional diet formulated with high levels of soybean meal and supplemented with Bacillus sp2 could be an alternative to protect Nile tilapia cultures from A. hydrophila infections and improve fish growth performance.

Co-infection of Lactococcus garvieae and Aeromonas hydrophila in cultured Nile Tilapia in Kerala, India.

Co-infection of Lactococcus garvieae and Aeromonas hydrophila, has been confirmed from diseased Nile Tilapia (Oreochromis niloticus), Chithralada strain cultured in a freshwater rearing pond of Alappuzha district of Kerala, India. The aetiological agents behind the disease outbreak were bacteriologically proven and confirmed by 16SrRNA sequencing and phylogenetic analysis. PCR detection of the virulent genes, showed existence of adhesin and hemolysin in L. garvieae and aerolysin in A. hydrophila strain obtained. To fulfil Koch's postulates, challenge experiments were conducted and median lethal dose (LD50) of L. garvieae and A. hydrophila was calculated as 1 × 105.91 CFU per mL and 1 × 105.2 CFU per mL respectively. Histopathologically, eyes, spleen, and kidney were the predominantly infected organs by L. garvieae and A. hydrophila. Out of the 13 antibiotics tested to check antibiotic susceptibility, L. garvieae showed resistance to almost 7 antibiotics tested, with a resistance to Ciprofloxacin while A. hydrophila was found resistant to Streptomycin and Erythromycin. Understanding the complex interaction between Gram-positive and Gram-negative bacteria in the disease process and pathogenesis in fish host will contribute to efficient treatment strategies. As a preliminary investigation into this complex interaction, the present study is aimed at phenotypic and genotypic characterization, pathogenicity evaluation, and antibiotic susceptibility of the co-infecting pathogens in a diseased sample of freshwater-farmed Nile tilapia.

Nile Tilapia Skin Xenograft Versus Silver-Based Dressings in the Management of Partial-Thickness Burn Wounds: A Systematic Review and Meta-Analysis.

Background: Burns are a serious public health problem worldwide, causing high morbidity and mortality. This study aimed to compare two forms of treatment for partial skin burns and to determine whether one is superior to the other in terms of efficacy and benefits through a meta-analysis of randomized controlled trials. This article highlights the efficacy of tilapia skin in the treatment of burns. We performed a meta-analysis of 199 patients and highlighted the promising results that indicate the clinical relevance of this resource when we compared the cost of dressings with the daily need for dressing changes, healing potential, and reduction in pain level according to the VAS scale and reduced frequency of dressing changes. Methods: A search of PubMed, Cochrane Central, and LILACS was performed to identify randomized controlled trials comparing tilapia skin and silver-based dressings for treating burns. Studies involving overlapping populations and animals were excluded. The outcomes of interest were complete re-epithelialization, decreased pain level, and dressing change. Results: Summarize the article's main findings. Conclusions: Four randomized trials were included with a total of 199 patients with partial-thickness burns between the ages of 2 and 70 years. A total of 99 (49.74%) patients were treated with tilapia skin, and conventional treatment was used on 100 (50.25%) of the patients. Differences were found between the tilapia and silver-based treatments concerning re-epithelialization (MD -0.48; CI 95% -0.71 to -0.24; p < 0.01; I2 = 0%), decreased pain level (MD -0.79; CI 95% -1.10 to -0.47; p < 0.01; I2 = 0%), and dressing change outcome (MD -3.54; 95% CI -5.81 to -1.26; p = 0.02; I2 = 97%).

Optimizing UVC-LED application to improve the shelf life of vacuum-packed refrigerated stored Nile tilapia (Oreochromis niloticus) fillets.

Although ultraviolet-C light-emitting diode (UVC-LED) has proven antimicrobial effectiveness doses needed to reach it cause adverse effects on the physicochemical quality of fish, and thus, optimization studies are crucial to boost its industrial application. This study aimed to identify optimal UVC-LED conditions for maximum shelf life extension with the least possible quality changes of refrigerated stored tilapia fillets from a central composite rotatable design (CCRD). UVC-LED powers (1, 1.38, and 1.58 mW/cm2 ) and times (500, 1800, and 2700 s) were set on the CCRD, which generated 11 treatments, including three replicate experiments. Treatments were analyzed for total aerobic psychrotrophic count, lipid oxidation, instrumental color, and texture parameters on days 0, 2, 4, 7, 11, and 14. The UVC-LED affected shelf life and physicochemical parameters in a nonlinear fashion. UVC-LED-treated fish had increased shelf life by 2.80-4.76 days and increase or decrease in lipid oxidation (0.025-0.276 mg of malondialdehyde [MDA]/kg), total color change (∆E = 3.47-9.06), and hardness (1.31-8.51 N) over the refrigerated storage depending on specific UVC-LED conditions applied. The optimal UVC-LED condition was 0.97 mW/cm2 with 2503.6 s (2428.50 mJ/cm2 ), which increased the fillet's shelf life by 2.5-fold (2 days) while maintaining quality closer to the original throughout refrigerated storage, resulting in ∆E < 5, an increase of only 0.05 mg of MDA/kg, and preservation of the decrease in hardness by 3.38 N compared to its control counterparts. Therefore, it represents an eco-friendly technology that can easily scaled industrially to enhance the sustainable fish production chain. PRACTICAL APPLICATION: The high fish perishability is a global concern due to food safety risks and waste generation impacting the environment adversely, especially nowadays, where fish production and consumption have increased, and there are more evident efforts to sustainable production. UVC-LED is an eco-friendly technology with proven antimicrobial effectiveness but doses needed to reach this effect enhance oxidative degradation. Despite that, optimization studies concerning the maximum shelf life extension while retaining the physicochemical quality of refrigerated stored fish are a gap in the literature and a barrier to its industrial application. Our findings are helpful in sustainably enhancing the fish production chain.

Evaluation of physicochemical properties of Nile tilapia skin collagen extracted in acid médium / Avaliação das propriedades físico-químicas do colágeno da pele de tilápia do Nilo extraído em meio ácido

Tilapia has high-temperature tolerance, can breed in captivity, grow fast, and have excellent cost-benefit. Because of these characteristics, this species is of great interest in aquaculture and, currently, the most produced fish in Brazil. However, by increasing tilapia production, there was also a rise in the amount of organic waste, mainly from filleting, which discards 70% of waste. There are many studies on collagen extraction from tilapia skin as an alternative to reduce these residues and add commercial value. In this work, the extraction of protein concentrate was tested using an acid protocol, in which the tilapia skins underwent a pre-treatment in an acid medium and saline precipitation, with variations in time and concentration. After its extraction, the skin was evaluated for ash, moisture, protein, solubility, and pH. The protein concentrate obtained showed low ash contents, and the humidity is within those presented by the literature. The protein concentrate showed levels from 68.73 to 80.58% of protein and a low solubility between 4.03 to 6.93%. In conclusion, acid extraction is a possible means of collagen extraction, and tilapia skin is a good alternative to reuse waste generated in the fish industry.

A tilápia tem tolerância a altas temperaturas, pode se reproduzir em cativeiro, crescer rápido e tem excelente custo-benefício. Por essas características, esta espécie é de grande interesse na aquicultura e, atualmente, o pescado mais produzido no Brasil. No entanto, com o aumento da produção de tilápias, houve também um aumento na quantidade de resíduos orgânicos, principalmente da filetagem, que descarta 70% dos resíduos. Existem muitos estudos sobre a extração de colágeno da pele de tilápia como alternativa para reduzir esses resíduos e agregar valor comercial. Neste trabalho, a extração do concentrado protéico foi testada utilizando um protocolo ácido, no qual as peles de tilápia foram submetidas a um pré-tratamento em meio ácido e precipitação salina, com variações de tempo e concentração. Após sua extração, a pele foi avaliada quanto a cinzas, umidade, proteína, solubilidade e pH. O concentrado protéico obtido apresentou baixos teores de cinzas, e a umidade está dentro dos apresentados pela literatura. O concentrado protéico apresentou teores de 68,73 a 80,58% de proteína e uma baixa solubilidade entre 4,03 a 6,93%. Em conclusão, a extração ácida é um possível meio de extração de colágeno, e a pele de tilápia é uma boa alternativa para reaproveitar os resíduos gerados na indústria de pescados.

Morphometric and gut microbial evaluation of Tilapia (Oreochromis niloticus) fed on different levels of Moringa oleifera / Avaliação morfométrica e microbiana intestinal de tilápia (Oreochromis niloticus) alimentada com diferentes níveis de Moringa oleifera

In current study, different feeding levels of Moringa oleifera formulated diet was compared to analyze the growth performance, feed conversion ratio, feed conversion efficiency and gut microbiology of Oreochromis niloticus. The study was comprised of four treatment groups including 4%, 8% and 12% Moringa oleifera and one control group which was devoid of Moringa leaves. The experimental trial was conducted at the Zoology laboratory of Pakistan Institute of Applied and Social Sciences, (PIASS) Kasur. The physicochemical parameters of water such as temperature, dissolve oxygen, pH, total dissolved solids and salinity in all aquaria were found non-significantly different from each other. In control condition T1, the average weight gain was 14.89±16.90a grams, while average length gain was 11.52±7.444a cm. However, the total viable count on Eosin methylene blue was 7.4×107, 5.8×107 on Tryptic soy agar and 5.8×107on Nutrient agar. In T2, the average weight gain was 16.22±16.09b grams and average length gain was 12.97±7.79b cm. The total viable count on Eosin methylene blue was 7×107, 5.5×107 on Tryptic soy agar and 5.8×107on Nutrient agar. In T3, the average weight gain was 37.88±27.43c grams, while the average length gain was recorded as 16.48±12.56c cm. However, the total viable count for treatment 3 was 6.4×10 on Eosin methylene blue, 4.8×107 on Tryptic soy agar and 5.2×107on Nutrient agar. In T4, the average weight gain was 44.22±31.67d grams, while the average length gain was 15.25±10.49d cm. The total viable count was 4.3×107on Eosin methylene blue, 3.1×107 on Tryptic soy agar and 3.8×107 on Nutrient agar. The effect of Moringa oleifera on the growth of Oreochromis niloticus was found to be significant and 12% Moringa extract showed maximum length and weight gain and minimum feed conversion ratio with the least microbial count in fish intestine.

No presente estudo, diferentes níveis de alimentação da dieta formulada com Moringa oleifera foram comparados para analisar o desempenho de crescimento, taxa de conversão alimentar, eficiência de conversão alimentar e microbiologia intestinal de Oreochromis niloticus. O estudo foi composto por quatro grupos de tratamento, incluindo 4%, 8% e 12% de Moringa oleifera e um grupo de controle sem folhas de Moringa. O ensaio experimental foi realizado no laboratório de Zoologia do Instituto de Ciências Aplicadas e Sociais do Paquistão (PIASS), Kasur. Os parâmetros físico-químicos da água como temperatura, oxigênio dissolvido, pH, sólidos totais dissolvidos e salinidade em todos os aquários foram encontrados não significativamente diferentes entre si. Na condição controle T1, o ganho médio de peso foi de 14,89±16,90a gramas, enquanto o ganho médio de comprimento foi de 11,52±7,444a cm. No entanto, a contagem total viável em azul de metileno de eosina foi de 7,4×107, 5,8×107 em ágar de soja Tryptic e 5,8×107 em ágar Nutriente. Em T2, o ganho médio de peso foi de 16,22±16,09b gramas e o ganho médio de comprimento foi de 12,97±7,79b cm. A contagem total viável em azul de metileno de eosina foi 7×107, 5,5×107 em ágar de soja Tryptic e 5,8×107 em ágar Nutriente. Em T3, o ganho médio de peso foi de 37,88±27,43c gramas, enquanto o ganho médio de comprimento foi registrado como 16,48±12,56c cm. No entanto, a contagem total viável para o tratamento 3 foi de 6,4×10 em azul de metileno de eosina, 4,8×107 em ágar soja Tryptic e 5,2×107 em ágar Nutriente. Em T4, o ganho médio de peso foi de 44,22±31,67d gramas, enquanto o ganho médio de comprimento foi de 15,25±10,49d cm. A contagem total viável foi de 4,3×107 em Eosin metileno blue, 3,1×107 em Tryptic soy agar e 3,8×107 em Nutrient agar. O efeito da Moringa oleifera no crescimento de Oreochromis niloticus foi significativo e o extrato de Moringa a 12% apresentou ganho máximo de comprimento e peso e conversão alimentar mínima com a menor contagem microbiana no intestino dos peixes.

Application of films developed with tilapia gelatin (Oreochromis niloticus), added with pitomba plant extract (Talisia esculenta) in Hawaii papaya.

In the present study, a film based on the gelatin skin of tilapia (Oreochromis niloticus) was developed, using surfactants and adding plant extract of pitomba seed (Talisia esculenta). The aim was to investigate the mechanical and barrier properties of the cover, as well as its effectiveness in conserving papayas against diseases caused by fungi. The film presented tensile strength of 38.78 MPa, elongation of 120.49%, and water vapor permeability of 5.90 g.mm.h-1.m2.kPa-1 when equally composed of SDS and Tween 80, in a percentage of 40% in relation to the total mass of the film. The films lasted 12 d in an environment with a relative humidity of 75% (25 ºC), longer than the shelf life of papaya (limited to 8 d). With applying the film with the extract, the incidence of diseases such as anthracnose, fusariosis, and stem rot caused by these microorganisms in papaya was reduced.

Performance of collagen-based matrices from Nile tilapia skin: A pilot proteomic study in a murine model of wound healing.

Full-thickness cutaneous trauma, due to the lack of dermis, leads to difficulty in epithelialization by keratinocytes, developing a fibrotic scar, with less elasticity than the original skin, which may have disorders in predisposed individuals, resulting in hypertrophic scar and keloids. Biomedical materials have excellent characteristics, such as good biocompatibility and low immunogenicity, which can temporarily replace traditional materials used as primary dressings. In this work, we developed two dermal matrices based on Nile tilapia collagen, with (M_GAG) and without (M) glycosaminoglycans, using a sugarcane polymer membrane as a matrix support. To assess the molecular mechanisms driving wound healing, we performed qualitative proteomic analysis on the wound bed in an in vivo study involving immunocompetent murine models at 14 and 21 days post-full-thickness skin injury. Gene Ontology and Pathway analysis revealed that both skins were markedly represented by modulation of the immune system, emphasizing controlling the acute inflammation response at 14 and 21 days post-injury. Furthermore, both groups showed significant enrichment of pathways related to RNA and protein metabolism, suggesting an increase in protein synthesis required for tissue repair and proper wound closure. Other pathways, such as keratinization and vitamin D3 metabolism, were also enriched in the groups treated with M matrix. Finally, both matrices improved wound healing in a full post-thick skin lesion. However, our preliminary molecular data reveals that the collagen-mediated healing matrix lacking glycosaminoglycan (M) exhibited a phenotype more favorable to tissue repair, making it more suitable for use before skin grafts.

Sequencing and multiple antimicrobial resistance of Pseudomonas fluorescens isolated from Nile tilapia fish in Egypt / Sequenciamento e resistência antimicrobiana múltipla de Pseudomonas fluorescens isoladas de tilápia-do-nilo no Egito

Pseudomonas fluorescens is one of the main causes of septicemic diseases among freshwater fish, causing severe economic losses and decreasing farm efficiency. Thus, this research was aimed to investigate the occurrence of P. fluorescens in Nile Tilapia (O. niloticus) fish in Egypt, gene sequencing of 16SrDNA gene, and antimicrobial susceptibility. P. fluorescens strains were detected in 32% (128/400) of apparently healthy (9%; 36/400) and diseased (23%; 92/400) Nile tilapia fish. The highest prevalence was observed in gills of fish, 31.3% followed by intestine 26.9%, liver 24.2%, and kidneys 17.6%. The PCR results for the 16SrDNA gene of P. fluorescens showed 16SrDNA gene in 30% of examined isolates. Moreover, Homogeny and a strong relationship between strains of P. fluorescens was confirmed using 16SrDNA sequences. Beside the responsibility of 16SrDNA gene on the virulence of P. fluorescens. The results of antimicrobial susceptibility tests revealed that all strains were resistant to piperacillin (100%), followed by ceftazidime (29.7%), and cefepime (25.8%). The strains of P. fluorescence were highly sensitive to cefotaxime (74.2%), followed by ceftriaxone and levofloxacin (70.3% each). Interestingly, 29.7% of strains of P. fluorescens were multiple antimicrobial-resistant (MAR).

Pseudomonas fluorescens é uma das principais causas de doenças septicêmicas em peixes de água doce, causando graves perdas econômicas e diminuindo a eficiência da fazenda. Assim, esta pesquisa teve como objetivo investigar a ocorrência de P. fluorescens em peixes de tilápia-do-nilo (O. niloticus) no Egito, sequenciamento do gene 16S rDNA e suscetibilidade antimicrobiana. Cepas de P. fluorescens foram detectadas em 32% (128/400) de peixes tilápia-do-nilo aparentemente saudáveis ​​(9%; 36/400) e doentes (23%; 92/400). A maior prevalência foi observada nas brânquias dos peixes, 31,3%, seguida pelo intestino 26,9%, fígado 24,2% e rins 17,6%. Os resultados da PCR para o gene 16SrDNA de P. fluorescens mostraram o gene 16SrDNA em 30% dos isolados examinados. Além disso, a homogeneidade e uma forte relação entre cepas de P. fluorescens foi confirmada usando sequências de 16SrDNA. Além da responsabilidade do gene 16SrDNA na virulência de P. fluorescens. Os resultados dos testes de suscetibilidade antimicrobiana revelaram que todas as cepas foram resistentes à piperacilina (100%), seguida pela ceftazidima (29,7%) e cefepima (25,8%). As cepas de P. fluorescens foram altamente sensíveis à cefotaxima (74,2%), seguida pela ceftriaxona e levofloxacina (70,3% cada). Curiosamente, 29,7% das cepas de P. fluorescens eram multirresistentes a antimicrobianos (MAR).

Sequencing and multiple antimicrobial resistance of Pseudomonas fluorescens isolated from Nile tilapia fish in Egypt

Abstract Pseudomonas fluorescens is one of the main causes of septicemic diseases among freshwater fish, causing severe economic losses and decreasing farm efficiency. Thus, this research was aimed to investigate the occurrence of P. fluorescens in Nile Tilapia (O. niloticus) fish in Egypt, gene sequencing of 16SrDNA gene, and antimicrobial susceptibility. P. fluorescens strains were detected in 32% (128/400) of apparently healthy (9%; 36/400) and diseased (23%; 92/400) Nile tilapia fish. The highest prevalence was observed in gills of fish, 31.3% followed by intestine 26.9%, liver 24.2%, and kidneys 17.6%. The PCR results for the 16SrDNA gene of P. fluorescens showed 16SrDNA gene in 30% of examined isolates. Moreover, Homogeny and a strong relationship between strains of P. fluorescens was confirmed using 16SrDNA sequences. Beside the responsibility of 16SrDNA gene on the virulence of P. fluorescens. The results of antimicrobial susceptibility tests revealed that all strains were resistant to piperacillin (100%), followed by ceftazidime (29.7%), and cefepime (25.8%). The strains of P. fluorescence were highly sensitive to cefotaxime (74.2%), followed by ceftriaxone and levofloxacin (70.3% each). Interestingly, 29.7% of strains of P. fluorescens were multiple antimicrobial-resistant (MAR).

Resumo Pseudomonas fluorescens é uma das principais causas de doenças septicêmicas em peixes de água doce, causando graves perdas econômicas e diminuindo a eficiência da fazenda. Assim, esta pesquisa teve como objetivo investigar a ocorrência de P. fluorescens em peixes de tilápia-do-nilo (O. niloticus) no Egito, sequenciamento do gene 16S rDNA e suscetibilidade antimicrobiana. Cepas de P. fluorescens foram detectadas em 32% (128/400) de peixes tilápia-do-nilo aparentemente saudáveis (9%; 36/400) e doentes (23%; 92/400). A maior prevalência foi observada nas brânquias dos peixes, 31,3%, seguida pelo intestino 26,9%, fígado 24,2% e rins 17,6%. Os resultados da PCR para o gene 16SrDNA de P. fluorescens mostraram o gene 16SrDNA em 30% dos isolados examinados. Além disso, a homogeneidade e uma forte relação entre cepas de P. fluorescens foi confirmada usando sequências de 16SrDNA. Além da responsabilidade do gene 16SrDNA na virulência de P. fluorescens. Os resultados dos testes de suscetibilidade antimicrobiana revelaram que todas as cepas foram resistentes à piperacilina (100%), seguida pela ceftazidima (29,7%) e cefepima (25,8%). As cepas de P. fluorescens foram altamente sensíveis à cefotaxima (74,2%), seguida pela ceftriaxona e levofloxacina (70,3% cada). Curiosamente, 29,7% das cepas de P. fluorescens eram multirresistentes a antimicrobianos (MAR).

Staphylococcus haemolyticus and Providencia vermicola Infections Occurring in Farmed Tilapia: Two Potentially Emerging Pathogens.

This work aimed to determine the presence of bacterial pathogens in fish with a clinical picture suggestive of infectious disease in Nile tilapia reared in Chiapas, Mexico. Blood and viscera samples were taken from healthy and diseased animals from commercial farms. Clinical and pathological examinations of each individual were performed and samples were collected for bacteriological studies. The bacterial isolates were identified and characterized by culture, biochemical tests, antibiogram, challenge tests and 16S rRNA sequencing. Staphylococcus haemolyticus and Providencia vermicola were isolated from various diseased organisms. The clinical picture caused by Staphylococcus haemolyticus was characterized by appetite disorders, neurological signs, nodulation or ulceration in different areas and congestion or enlargement of internal organs. Providenciosis in juvenile specimens caused a characteristic picture of hemorrhagic septicemia. Challenge tests performed in healthy organisms revealed that both infections caused higher mortality rates in fish (p < 0.05) compared with non-infected specimens, with 100% survival. There was 100% mortality for animals infected with P. vermicola after three days post infection and 45% for those infected with S. haemolyticus. The isolation and identification of two pathogens involved in an infection process were achieved and cataloged as potential causal agents of disease outbreaks in tilapia farming in Mexico. This is the first report of possible bacterial infection caused by S. haemolyticus and P. vermicola in tilapia farms, which are two uncommon but potentially emerging pathogens for the species.

Unveiling the Probiotic Potential of the Anaerobic Bacterium Cetobacterium sp. nov. C33 for Enhancing Nile Tilapia (Oreochromis niloticus) Cultures.

The bacterium strain Cetobacterium sp. C33 was isolated from the intestinal microbial content of Nile tilapia (O. niloticus) under anaerobic conditions. Given that Cetobacterium species are recognized as primary constituents of the intestinal microbiota in cultured Nile tilapia by culture-independent techniques, the adaptability of the C33 strain to the host gastrointestinal conditions, its antibacterial activity against aquaculture bacterial and its antibiotic susceptibility were assessed. The genome of C33 was sequenced, assembled, annotated, and subjected to functional inference, particularly regarding pinpointed probiotic activities. Furthermore, phylogenomic comparative analyses were performed including closely reported strains/species relatives. Comparative genomics with closely related species disclosed that the isolate is not phylogenetically identical to other Cetobacterium species, displaying an approximately 5% sequence divergence from C. somerae and a 13% sequence divergence from Cetobacterium ceti. It can be distinguished from other species through physiological and biochemical criteria. Whole-genome annotation highlighted that Cetobacterium sp. nov. C33 possesses a set of genes that may contribute to antagonism against competing bacteria and has specific symbiotic adaptations in fish. Additional in vivo experiments should be carried out to verify favorable features, reinforcing its potential as a probiotic bacterium.

Characterization and finding the origin of off-flavor compounds in Nile tilapia cultured in net cages in hydroelectric reservoirs, São Paulo State, Brazil.

An increasing demand for fish products has led to an intensive aquaculture production in Brazil, and cultivation of fish constituted 860 × 103 tons in 2022, contributing to the 87% of total fish consumption. Nile tilapia constitutes almost half of the aquaculture production, and most tilapia farms use floating net cages. One of the major constraints of intensive fish production is production of off-flavors. Release of nutrients by the fish leads to deterioration of the water quality and stimulates growth of microorganisms, also including off-flavor producing species. The objective of this study was to determine levels of taste and odor compounds (geosmin, 2-MIB and a selection of volatile compounds) and their impact on the flavor quality of Nile tilapia produced in net cages in reservoirs in São Paulo State, Brazil. GC-MS analysis of fish and water from six different farms showed concentrations of geosmin in the water from 1 to 8 ng/L, while geosmin in fish flesh ranged from 40 to 750 ng/kg. The level of 2-MIB in water was 2 to 25 ng/L, and 0 to 800 ng/kg fish. The GC-MS analysis also revealed presence of more than 100 volatile organic compounds in the fish flesh, consisting of aldehydes, alcohols, benzene derivatives, hydrocarbons, ketones and few other compounds. Geosmin and 2-MIB related flavor notes were detected in all fish by a sensory panel, and a high correlation between the chemical and sensory analyses was found. The potential impact of the volatile organic compounds on the fish flavor is discussed. Analysis of the water quality in the reservoirs indicated that levels of geosmin and 2-MIB levels were highly influenced by the nutrient levels in the water.

Stress-associated ß -glucan administration stimulates the TLR - MYD88 - NFKB1 signaling pathway in Nile tilapia (Oreochromis niloticus).

There is evidence that the administration of ß-glucan can effectively activate several defense mechanisms, such as the Tlr-Myd88-Nfkb1 pathway that induces the expression of immune cytokines. Thus, the objective of this work was to evaluate whether ß-glucan acts on the mechanisms of gene transcription via the Tlr-Myd88-Nfkb1 pathway in Nile tilapia under stress after challenge with Streptococcus agalactiae. Therefore, we evaluated the expression of immune system genes such as toll-like receptors 1 (tlr1), toll-like receptors 2 (tlr2), primary myeloid differentiation response gene (myd88) and nuclear factor kappa B1 (nfkb1). A total of 408 fish were distributed in 24 polyethylene boxes and randomly divided into eight groups with 3 replications each: C15: Tilapias received a control diet (free of ß-glucan) for 15 days and were sampled after the 15th day of the experiment; C15D: Tilapias received a control diet (free of ß-glucan) for 15 days, were challenged on the 14th day and were sampled at the 15th day of the experiment; ß15: Tilapias received experimental diet (1g kg-1 of ß-glucan) for 15 days and were sampled after 15 days; ß15D: Tilapias received an experimental diet (1g kg-1 of ß-glucan) for 15 days, were challenged on the 14th day and were sampled at the 15th day of the experiment; C30: Tilapias received a control diet (free of ß-glucan) for 30 days and were sampled on the 30th day of the experiment; C30D: Tilapias received a control diet (free of ß-glucan) for 30 days, were challenged on the 29th day and were sampled at the 30th day of the experiment; ß30: Tilapias received experimental diet (1g kg-1 of ß-glucan) for 30 days and were sampled after 30 days and ß30D: Tilapias received experimental diet (1g kg-1 of ß-glucan) for 30 days, were challenged on the 29th day and were sampled at 30 of the experiment. In the fish sampled at 15 and 30 days of the experiment, after being anesthetized and killed by brain section, cranial kidney and spleen were collected for gene expression analysis. The analyzes showed that the association of ß-glucan and stressful management modulated the immune system, using the Tlr-Myd88-Nfkb1 signaling pathway, indicating that this compound can be used to promote early defense and protect fish against diseases.

l-Threonine production from whey and fish hydrolysate by E. coli ATCC® 21277TM.

In this work production of l-threonine by Escherichia coli ATCC® 21277™ has been studied using a mixture of alternative low-cost substrates, which are recognized to be a major pollution problem. Whey was used as the primary carbon source, whereas Red Tilapia (Oreochromis sp.) viscera hydrolysates constituted the nitrogen source. A Box-Behnken Design was used for optimizing l-threonine and biomass production, using temperature and glucose, whey, and Red Tilapia (Oreochromis sp.) viscera hydrolysate contents as factors. Results indicate that biomass production is affected by the concentration of hydrolysate and temperature. On the other hand, l-threonine production is affected by concentration of whey, hydrolysate, and temperature. In this context, it was possible to maximize l-threonine production, but with a detriment on biomass production. The optimal conditions for biomass and l-threonine maximization (after 24 h) were identified and validated experimentally, resulting in biomass and l-threonine production of 0.767 g/L and 0.406 g/L, respectively. This work has shown the technical feasibility of using whey and Red Tilapia (Oreochromis sp.) viscera hydrolysates for the production of l-threonine by E. coli ATCC® 21277TM. Finally, the complications associated to the use of these low-cost complex substrates for the production of l-threonine by E. coli, suggest that more in detail studies (i.e. at the metabolic level) are required in order to propose strategies to increase the process productivity, before its scale up. This is a first step in our long-term goal of developing a production process for i) dealing with the pollution problems caused by those wastes, and ii) strengthen the milk and fish industries which are important poles of the Colombian economy.

Residue Depletion Profile and Estimation of Withdrawal Period for Sulfadimethoxine and Ormetoprim in Edible Tissues of Nile Tilapia (Oreochromis sp.) on Medicated Feed.

Sulfadimethoxine (SDM) and ormetoprim (OMP) are antimicrobials used in combination to treat bacterial infections in fish farming. The use of this drug combination is not yet regulated in some countries, such as Brazil. Due to the lack of regulated drugs for aquaculture in Brazil, this study investigated the residue depletion profile of SDM and OMP in Nile tilapia (Oreochromis sp.) after oral administration. Fish were treated with medicated feed containing a 5:1 ratio of SDM:OMP at the dose of 50 mg kg BW-1 for five consecutive days with an average water temperature of 28 °C. The drugs were incorporated into the feed by using a gelatin coating process which promoted homogeneity in drug concentration and prevented the drug leaching into the water during medication. The SDM and OMP determination in fish fillets (muscle plus skin in natural proportions) was performed using the QuEChERS approach followed by LC-MS/MS quantification. The analytical method was validated according to Brazilian and selected international guidelines. A withdrawal period of 9 days (or 252 °C days) was estimated for the sum of SDM and OMP residues at concentration levels below the maximum residue level of 100 µg kg-1.

First Report of Aeromonas veronii as an Emerging Bacterial Pathogen of Farmed Nile Tilapia (Oreochromis niloticus) in Brazil.

Brazil is one of the world's leading producers of Nile tilapia, Oreochromis niloticus. However, the industry faces a major challenge in terms of infectious diseases, as at least five new pathogens have been formally described in the last five years. Aeromonas species are Gram-negative anaerobic bacteria that are often described as fish pathogens causing Motile Aeromonas Septicemia (MAS). In late December 2022, an epidemic outbreak was reported in farmed Nile tilapia in the state of São Paulo, Brazil, characterized by clinical signs and gross pathology suggestive of MAS. The objective of this study was to isolate, identify, and characterize in vitro and in vivo the causative agent of this epidemic outbreak. The bacterial isolates were identified as Aeromonas veronii based on the homology of 16S rRNA (99.9%), gyrB (98.9%), and the rpoB gene (99.1%). A. veronii showed susceptibility only to florfenicol, while it was resistant to the other three antimicrobials tested, oxytetracycline, enrofloxacin, and amoxicillin. The lowest florfenicol concentration capable of inhibiting bacterial growth was ≤0.5 µg/mL. The phenotypic resistance of the A. veronii isolate observed for quinolones and tetracycline was genetically confirmed by the presence of the qnrS2 (colE plasmid) and tetA antibiotic-resistant genes, respectively. A. veronii isolate was highly pathogenic in juvenile Nile tilapia tested in vivo, showing a mortality rate ranging from 3 to 100% in the lowest (1.2 × 104) and highest (1.2 × 108) bacterial dose groups, respectively. To our knowledge, this study would constitute the first report of highly pathogenic and multidrug-resistant A. veronii associated with outbreaks and high mortality rates in tilapia farmed in commercial net cages in Brazil.

Evaluation of the healing potential of Nile tilapia skin collagen in traumatic oral ulcers in male rats.

OBJECTIVE: To evaluate the healing potential of Nile tilapia skin collagen using a rat model with experimentally induced traumatic oral ulcers. DESIGN: Male Wistar rats were segregated into three experimental groups (n = 8/group/euthanasia day). Ulcers were induced using a dermatological punch on the left buccal mucosa. The rats were then euthanized on days 1, 5, 10, 15, and 20 (ntotal=120 rats). Each group received topical treatment, 2x/day, with 1 % Nile tilapia skin collagen orabase (experimental group), only orabase (negative control), or Oncilom-A® orabase (positive control). Ulcer area, closure percentage, and body mass variation were measured. Slides were prepared for histological analysis, which included Picrosirius red staining (collagen analysis), and immunohistochemistry (platelet endothelial cell adhesion molecule, alpha-smooth muscle actin, and transforming growth factor-beta). RESULTS: On day 15, the experimental and positive control groups displayed smaller ulcer areas, a higher percentage of closure, complete re-epithelialization, superior histological repair scores, and a reduced count of polymorphonuclear cells in comparison to the negative control group (p < 0.05). Additionally, the experimental group exhibited an increased number of blood vessels, total collagen (types I and III) and expression of platelet endothelial cell adhesion molecule, alpha-smooth muscle actin, and transforming growth factor-beta relative to the negative and positive control groups (p < 0.05). By day 20, the experimental group showed a more significant weight gain compared to the other groups (p < 0.0001). CONCLUSIONS: Nile tilapia skin collagen orabase optimizes the healing of traumatic ulcers by stimulating re-epithelialization, angiogenesis, and collagenesis. Transforming growth factor-beta plays a significant role in this process.