BEYOND ANTIBIOTICS: PROBIOTICS, PREBIOTICS, AND SYMBIOTICS IN FRESHWATER AQUACULTURE – A REVIEW

Simple SummaryThe application of probiotics, prebiotics and synbiotics as functional feed additives has created increasing attention towards environment-friendly aquaculture. In this study, the effects of autochthonous Bacillus spp. (probiotics) and fructooligosaccharide (FOS, prebiotic) have been evaluated, either alone or in combination (synbiotics), for an Indian major carp (rohu), Labeo rohita fingerlings. The results indicated that the combination of B. licheniformis and FOS significantly improved live weight gain, feed utilisation and protease activity in fish compared to the other groups. In general, probiotics- and synbiotics-supplemented groups exhibited improved haematology, serum biochemical profiles and immune parameters compared to the control group. After 90 days of feeding, the fish were experimentally exposed to a pathogenic bacterium, Aeromonas hydrophila. Data on the haematology, immunity and stress parameters revealed that synbiotics application boosted immunity and relieved physiological stress in fish. The highest survival among the pathogen-infected fish was recorded with the dietary application of synbiotics consisting of B. licheniformis and FOS. In addition, fish fed a combination of B. methylotrophicus and FOS in their diets also survived well. Thus, we suggest the application of synbiotics containing autochthonous bacilli and FOS to improve growth, immunity and pathogen resistance in fish.The effects of Bacillus spp. (7 Log CFU g−1 feed) and fructooligosaccharide (FOS, 1%) as functional feed additives, either alone or in combination, were evaluated in a study on rohu, Labeo rohita fingerlings. The fish were fed different diets for 90 days, including a control diet and diets supplemented with FOS, B. licheniformis, B. methylotrophicus or synbiotic formulations of these. The results showed that the combination of B. licheniformis and FOS significantly improved weight gain, feed utilisation and protease activity compared to the other groups. Overall, the groups supplemented with probiotics and synbiotics (B. licheniformis + FOS or B. methylotrophicus + FOS) showed improvements in haematology, serum biochemistry and immune parameters compared to the control group. After 90 days of experimental feeding, the fish were challenged with pathogenic Aeromonas hydrophila, and data on haematology, immunity and stress parameters were collected. The results indicated that the application of Bacillus spp. and FOS boosted immunity and resistance to physiological stress in the fish. The highest post-challenge survival rate was observed in fish fed a diet with B. licheniformis and FOS, indicating the potential of this particular combination of functional feed additives to enhance growth, immunity and disease resistance in L. rohita.

This study aimed to analyze the effect of herbal extracts as functional feed additives on the utilization of feed and growth performance of orange mud crabs (Scylla olivacea). The test animals used were 60 crabs for each treatment dose. The crabs are kept individually in a crab box which was placed on a floating bamboo raft. This was to enable floating on the surface of the pond water which had a depth of ±80 cm. The treatments tested were four doses of a combination herbal extract from Morus alba, Curcuma xanthorrhiza, and Boesenbergia rotunda, namely 0, 200, 400, 600 mg kg-1 of feed. Formulated feed with the protein content of 41.93%, fat 7.43%, Nitrogen Free Extract (NFE) 29.33%, and crude fiber 7.82% was given at a dose of 5% body weight every day. Based on one-way ANOVA, the results showed that the dose of herbal extracts influences the feed utilization and growth performance of mud crabs. The dose of herbal extract 600 mg kg-1 of feed provided higher feed utilization and growth performance (LSD Test: P<0.1). Significant differences were found between feed utilization and growth performance of mud crabs after molting and non-molting. In molting mud crabs, treatment with herbal extract 600 mg kg-1 obtained an average weight gain of ±60.73 from the initial weight, compared to control crabs (without herbal extracts) gaining an average weight gain of ±43.73%. However, in non-molting crabs, ±5.44 and ±6.42 weight gain was observed, respectively. Significant differences also occurred between treatments for specific growth rates, feed consumption, feed efficiency, and condition factors. These results provided information that herbal extracts are potentially as feed additives to increase feed utilization and growth performance, as well as stimulate molting in crab cultivation.

Probiotics, Prebiotics and Synbiotics for Nile tilapia: Growth performance and protection against Aeromonas hydrophila infection

Dietary ferulic acid boosts the immunity and antioxidant activity of T lymphocytes in Nile tilapia (Oreochromis niloticus) challenged with Aeromonas hydrophila.

Considering the costs of feed costs (nearly 60% of production cost), nutrition, feeding and feed utilization are among the most important factors in commercial aquaculture. During the last decade, administration of functional feed additives has been practiced for enhancing nutrient digestibility and digestive enzyme activities of cultured fish and shellfish. Traditionally, antibiotics were used for boosting growth performance and nutrient digestibility in commercial aquaculture. However, emergence of resistance pathogens and possible risk to human health resulted in limitation or prohibition of prophylactic administration of antibiotics. Recently, there was increasing attentions towards dietary administration of functional feed additives that include probiotics, prebiotics and synbiotics for elevation of digestive enzyme activity and nutrient digestibility. The results of those studies revealed contradictory effects of different pro-, pre- or synbiotics on various fish species. It seems that the effects are species specific and related to modulation of the intestinal microbiota. In view of this issue, the present review provides a comprehensive sight on the effects of different pro-, pre- and synbiotics on digestive enzyme activity and nutrient digestibility in different species with special focus on the mode of action. In addition, the present review highlighted the gaps of existing knowledge as well as suggesting the subjects which needs additional studies.

Aquaculture is a crucial and rapidly expanding industry in global food production. Fisheries are also an essential socio-economic activity, providing abundant resources and remarkable prospects. However, due to the deteriorating ecological environment, aquatic animals are often exposed to traumatic conditions and are susceptible to bacterial infections that pose significant challenges for aquaculture production. The indiscriminate use of antibiotics in the past has led to the emergence of multidrug-resistant pathogens and sudden outbreaks of infectious diseases, resulting in serious economic losses. Moreover, the use of expensive chemotherapeutic drugs and antibiotics has negative impacts on aquatic environments. Therefore, it is increasingly important to adopt alternative natural agents, such as probiotics and their metabolites, to enhance healthy fish production. Probiotics are microorganisms that have numerous beneficial effects on their hosts. They are environmentally friendly, non-toxic, and cost-effective. This review specifically focuses on the use of Bacillus sp. as probiotics to promote healthy tilapia production in the aquatic sector, while also examining their interactions with the immune system and gut micro-biota. The information presented in this review can guide future research and promote effective and healthy tilapia culture production.

The gut microbiota (GM) is a complex and dynamic community of microorganisms that colonize the human gastrointestinal tract and play an important role in various aspects of the host’s physiology and health. GM is involved in digestion and assimilation of nutrients, synthesis of vitamins and metabolites, modulation of the immune system and defense against pathogens. However, the gut microbiota can also be a source of inflammation and disease when its composition and function are altered. This phenomenon, known as dysbiosis, is associated with almost all gastrointestinal diseases and is most prominent in inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), colorectal cancer, and celiac disease. Considering the important role of GM in the pathogenesis of IBD and other diseases of the gastrointestinal tract, several methods of its modification have been proposed, including the use of probiotics, prebiotics, synbiotics, antibiotics, dietary interventions, fecal microbiota transplantation (FTM) and bacteriophage therapy. However, drawing general conclusions about the efficacy and safety of these approaches is often difficult due to variability in interventions, doses, timing of administration, and the inevitable heterogeneity of host microbiome profiles and gut status. This review presents the results of a large international survey, purposed on the assessment of current practice, preferences, challenges, and expectations of doctors regarding the assessment of the composition of GM and the use of antibiotics, probiotics and TFM in intestinal diseases. The survey was also aimed on the identification of factors influencing the decision‑making process by doctors and barriers limiting the implementation of GM modification in clinical practice. Conclusions drawn from the results of the survey highlight the need for further research, standardization of techniques and evidence‑based recommendations to optimize the use of probiotics, antibiotics and TFM in clinical practice.

BackgroundWe analyzed the factors related to AAD to inform the rational use of antibiotics in critically ill patients and to reduce the incidence of AAD by providing a reference for antibiotic use in the clinical setting.Material/MethodsThis study was a retrospective analysis of the clinical data of patients who were hospitalized in the ICU of the First Teaching Hospital of Xi’an Jiaotong University from January 1, 2015 to December 31, 2016. Patients with AAD were assigned to the case group, and all others were assigned to the control group. Basic data were collected for all the selected patients. All the relevant data were analyzed with univariate or multivariate regression analyses, and P<0.05 was considered statistical significance.ResultsA total of 293 patients were enrolled. Statistical analyses showed that gender (OR 1.915; 95% [CI] 1.061–3.455; P=0.031), parenteral nutrition (OR 1.877; 95% [CI] 1.043–3.377; P=0.036), preventive use of probiotics (OR 0.497; 95% [CI] 0.285–0.866; P=0.014), APACHE II score upon admission to the ICU (OR 0.961; 95% [CI] 0.927–0.998; P=0.037) and use of enzyme-inhibitor antibiotics (OR 1.899; 95% [CI] 1.044–3.420; P=0.016) were associated with AAD. Further subgroup analysis by gender showed that parenteral nutrition (OR 2.144; 95% [CI] 1.064–4.322; P=0.033), preventive use of probiotics (OR 0.367; 95% [CI] 0.186–0.722; P=0.004), and APACHE II score upon admission to the ICU (OR 1.055; 95% [CI] 1.011–1.101; P=0.014) were associated with AAD in critically ill male patients. Age (OR 0.975; 95% [CI] 0.951–0.999; P=0.041) and use of carbapenem antibiotics (OR 4.826; 95% [CI] 1.011–23.030; P=0.048) were associated with AAD in critically ill female patients.ConclusionsParenteral nutrition, prophylactic use of probiotics, use of enzyme-inhibitor antibiotics, and use of combinations of antibiotics were associated with AAD in critically ill patients. The prophylactic use of probiotics may be a protective factor in AAD.

5 - Functional feed additives in aquaculture feeds

The effect of probiotic and synbiotic use on glycemic control in women with gestational diabetes: A systematic review and meta-analysis

This review aims to explore developments in the usage of multistrain probiotics in commercial freshwater‐cultured fish and to address factors that affect the efficacies of multistrain probiotics to enhance growth parameters, survival after bacterial infection and immune modulation in comparison to monostrain probiotics. From bibliographic searches in Scopus, Web of Science and PubMed, it was possible to select 81 articles that evaluated multistrain probiotics supplementation during in vivo trials in Nile tilapia (Oreochromis niloticus), rainbow trout (Oncorhynchus mykiss), common carp (Cyprinus carpio) and roho labeo (Labeo rohita). Most of the articles showed different benefits, including enhancement of fish growth performance, immune response and resistance against some pathogenic bacteria, such as Aeromonas hydrophila, Streptococcus agalactiae and Streptococcus iniae. However, only 13 journal articles included a monostrain probiotic as a control that would allow direct comparison with a probiotic bacterial mixture to determine if the mixture offered higher benefits in comparison to a monostrain probiotic and a control group without probiotic supplementation. Here we explain the main findings, including the best probiotic mixtures, and some perspectives on multistrain probiotics research and use on a commercial scale.

Background/Objectives: Traveler’s diarrhea (TD) is a pressing issue, affecting a significant portion of international travelers. Despite the guidelines discouraging routine use of antibiotics and the inconclusive evidence supporting probiotics for TD prevention, both remain popular prophylactic strategies. However, data on these practices among Polish tourists are currently lacking. The objective of this study was to assess the prevalence of probiotic and antibiotic use as preventive measures against TD among Polish travelers. Methods: A cross-sectional survey was conducted between July and August 2025 among adults with at least one international trip per year. An anonymous online questionnaire collected demographic data, travel frequency, and the use of probiotics and/or antibiotics for TD prophylaxis. Results: Of 873 respondents, 848 completed the questionnaire (median age: 35 years; 62.5% female). Probiotic use for TD prevention was reported by 24% of respondents (7.4% during all travels, 11.9% during trips outside of Europe, and 4.7% occasionally). Probiotic use was significantly associated with higher travel frequency, female sex, and younger age. Antibiotic use for TD prophylaxis was declared by 5.3% of participants, more common among those without comorbidities, with no significant association with age, sex, or travel frequency. Additionally, 21.6% of respondents reported regular, daily use of probiotics, though only 10.9% were recommended by physicians. Conclusions: This study’s findings reveal that a significant proportion of Polish travelers used probiotics for TD prevention, despite limited evidence and expert guidelines. A small subset of respondents used an antibiotic as TD prophylaxis. As global antibiotic resistance continues to rise, emphasizing antimicrobial stewardship in travel medicine practice is crucial. The fact that many individuals self-administer probiotics without medical consultation underscores the need for greater public education on the risks, benefits, and limitations of these interventions.

Probiotic use has skyrocketed in recent years. Little is known, however, about patient knowledge and practices regarding probiotic use, especially in the context of antibiotic use. An invitation to complete a short, anonymous, electronic survey was sent by email to 965 patients at a tertiary medical centre in California who had agreed to be contacted for participation in research studies. Questions were asked about both probiotic and antibiotic use in the prior three months. Of 333 survey respondents, 55% had recently used probiotics, including food products and/or supplements (90 and 60% of probiotic users, respectively). Women were more likely than men to have used probiotics (odds ratio (OR): 1.99; 95% confidence interval (CI): 1.2-3.4). Health care providers (HCP) had prescribed antibiotics to 79 (24%) respondents in the preceding three months. Among antibiotic users, 33% had initiated or changed probiotics at the time of antibiotic use, usually without a recommendation from their prescribing HCP (72%). Only 12% of those who took probiotics with antibiotics had received a specific recommendation from their HCP. Most patients chose to take probiotic mixtures (56%), with few selecting evidence-based strains, such as Lactobacillus rhamnosus GG (11%). Regular probiotic use among patients is common. Typically, these probiotics are not recommended by a HCP, even in conjunction with antibiotic prescriptions. While a growing body of evidence supports specific probiotic strains for the prevention of antibiotic-associated diarrhoea, patients are often not receiving a specific recommendation from their HCP and appear to be taking strains without guidance from supporting evidence.

This study aimed to evaluate the current status on the use of probiotics, disinfectants and antimicrobials in hatcheries, nurseries and grow-out farms producing Pangasius catfish (Pangasianodon hypophthalmus) in the Mekong Delta, Vietnam. Semi-structured interviews were conducted with 83 aquaculture enterprises (15 hatcheries, 32 nurseries and 36 grow-out farms). Farmers reported use of a total of 24 different antimicrobials, e.g. for treatment of bacillary necrosis and motile aeromonad septicaemia, and a variety of disinfectants, probiotics and nutritional supplements. In contrast to small-scale farmers, all large-scale grow-out farmers studied were certified and therefore had higher levels of formal education and specialized aquaculture training to diagnose and treat diseases. All farmers prepared their own medicated feed with a high risk of treatment failure, negative environmental impact from released antimicrobials and resistance development. Small-scale farmers were at particular occupational health risks when handling antimicrobials and other chemicals, e.g. mixing medicated feed with bare hands. There is an urgent need to improve knowledge and use innovative approaches, e.g. private-public partnerships, to assure a prudent use of chemicals, to improve capacity and access to disease diagnosis, particularly for small-scale grow-out farmers and nurseries. Efforts to control use of antimicrobials in aquaculture should be coordinated with the livestock and human health sectors taking an One-Health approach.

Background:When fish are immunosuppressed by handling stress, water quality, parasitism, or population density, they develop Aeromonosis. Aeromonas hydrophila is a Gram-negative bacterium that is found in water and can infect fish, frogs, and mammals, including humans. Aeromonas hydrophila is a major pathogen in freshwater aquaculture, causing significant economic losses and raising concerns about antimicrobial resistance due to excessive antibiotic use. Coconut oil, rich in lauric acid, has potential as a natural immunomodulatory feed additive.Aim:This study aimed to investigate the antibacterial effects of coconut oil against A. hydrophila through in vitro assays, assess its impact on zebrafish mortality and gut microbiota in vivo, and explore changes in immune-related protein profiles using Sodium Dodecyl Sulfate - Polyacrylamide Gel Electrophoresis (SDS-PAGE) analysis.Method:A post-test-only control group design was applied, utilizing 225 zebrafish divided into five groups. Three experimental groups received coconut oil-enriched diets at doses of 1,000, 2,000, and 4,000 mg/kg over a 60-day period, followed by immersion challenges with c (10⁸ CFU/ml). Antibacterial activity was evaluated using the disc diffusion method. Gut microbiota, including lactic acid bacteria, were isolated and identified on selective media, and protein expression profiling was conducted via SDS-PAGE.Result:Coconut oil did not demonstrate direct antibacterial effects against A. hydrophila up to 100% concentration. Nevertheless, zebrafish in groups T1 (1,000 mg/kg) and T3 (4,000 mg/kg) exhibited lower mortality rates compared to the positive control. Gut microbiota analyses identified A. hydrophila, Staphylococcus aureus, Pseudomonas aeruginosa, and Lactobacillus spp. SDS-PAGE revealed bands corresponding to proteins at approximately 85–90 kDa [likely heat shock proteins (HSPs)], 27.2–38 kDa (outer membrane proteins), and 44–48 kDa [epidermal growth factor (EGF)-like proteins]. Notably, T1 and T3 groups showed stronger EGF-like bands and a more stable gut microbiota profile, marked by elevated counts of Lactobacillus spp.Conclusion:Coconut oil lacks direct bactericidal activity against A. hydrophila but enhances host resistance by stabilizing gut microbiota and promoting the expression of defensive proteins such as HSP90 and EGF-like molecules. These findings highlight the potential of coconut oil as a non-antibiotic functional feed additive for sustainable aquaculture. Further large-scale and long-term studies are warranted to validate its efficacy.