Nayak Ashwath, Harshitha Mave, Dubey Saurabh, Munang'andu Hetron Mweemba, Chakraborty Anirban, Karunasagar Indrani, Maiti Biswajit
Division of Infectious Diseases, Nitte (Deemed to be University), Nitte University Centre for Science Education and Research, Paneer Campus, Deralakatte, Mangaluru, 575018, India.
Faculty of Veterinary Medicine, Department of Production Animal Clinical Sciences, Section of Experimental Biomedicine, Norwegian University of Life Sciences, Ås, Norway.
Probiotics Antimicrob Proteins. 2024 Oct;16(5):1623-1637. doi: 10.1007/s12602-023-10127-w. Epub 2023 Jul 24.
The indiscriminate use of antibiotics in aquaculture has led to the emergence of resistance; hence, eco-friendly, host-specific alternatives to mitigate bacterial infections have become imminent. In this study, bacteria that could possibly serve as probiotics were isolated and evaluated for their efficacy with in vitro experiments and in vivo zebrafish gut model. One isolate from each of the 23 rohu fish (Labeo rohita) was shortlisted after preliminary screening of several isolates and tested for their ability to inhibit two important warm water bacterial fish pathogens, Aeromonas hydrophila, and Edwardsiella tarda. An isolate (RODK28110C3) that showed broad-spectrum inhibitory activity against a battery of different isolates of the two fish pathogens included in this study and maintained in our repository was selected for further characterization. The culture was identified phenotypically as Bacillus subtilis and confirmed by 16S rDNA sequencing. The isolate was able to hydrolyze fish feed constituents that include starch, protein, and cellulose. Further in vitro tests ensured that the potential isolate with probiotic attributes could tolerate different gut conditions, which included a range of pH, salinity, and varying concentrations of bile salt. Exposure of 4 days post fertilization zebrafish embryos to the RFP-tagged isolate confirmed the colonization of B. subtilis in the gut of the zebrafish embryo, which is an important attribute of a probiotic. The isolate was able to inhibit both A. hydrophila and E. tarda in gnotobiotic zebrafish embryo in triplicate. The study demonstrates the probiotic characteristics of the B. subtilis isolated from L. rohita and its ability to inhibit A. hydrophila and E. tarda using in vitro conditions and in the zebrafish gut and could serve as an effective alternative to antibiotics in aquaculture.
水产养殖中抗生素的滥用导致了耐药性的出现；因此，开发环保、宿主特异性的替代方法来减轻细菌感染已变得迫在眉睫。在本研究中，分离出了可能用作益生菌的细菌，并通过体外实验和体内斑马鱼肠道模型评估了它们的功效。在对多个分离株进行初步筛选后，从23条印度鲤（Labeo rohita）中各选出一个分离株进入候选名单，并测试它们抑制两种重要的温水性鱼类细菌病原体——嗜水气单胞菌（Aeromonas hydrophila）和迟缓爱德华氏菌（Edwardsiella tarda）的能力。本研究筛选出了一株对多种不同的这两种鱼类病原体分离株具有广谱抑制活性且保藏在我们菌种库中的分离株（RODK28110C3），用于进一步表征。该培养物经表型鉴定为枯草芽孢杆菌（Bacillus subtilis），并通过16S rDNA测序进行了确认。该分离株能够水解包括淀粉、蛋白质和纤维素在内的鱼类饲料成分。进一步的体外试验证实，具有益生菌特性的潜在分离株能够耐受不同的肠道条件，包括一系列pH值、盐度以及不同浓度的胆汁盐。将受精后4天的斑马鱼胚胎暴露于红色荧光蛋白标记的分离株中，证实了枯草芽孢杆菌在斑马鱼胚胎肠道中的定殖，这是益生菌的一个重要特性。该分离株在无菌斑马鱼胚胎中能够重复抑制嗜水气单胞菌和迟缓爱德华氏菌。本研究证明了从印度鲤分离出的枯草芽孢杆菌的益生菌特性及其在体外条件下和斑马鱼肠道中抑制嗜水气单胞菌和迟缓爱德华氏菌的能力，并且可作为水产养殖中抗生素的有效替代品。
