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    Lactiplantibacillus argentoratensis and Candida tropicalis Isolated from the Gastrointestinal Tract of Fish Exhibited Inhibitory Effects against Pathogenic Bacteria of Nile Tilapia
    (2023-02-01)
    Siangpro, Noppadon
    ;
    Chuakrut, Songkran
    ;
    Sirimanapong, Wanna
    ;
    Tanasupawat, Somboon
    ;
    Phongsopitanun, Wongsakorn
    Nile tilapia is one of the most consumed farmed fish in the world. The outbreak of pathogenic bacterial diseases causes high mortality rates and economic losses in Nile tilapia farming. Antibiotic administrations are commonly utilized to inhibit and prevent bacterial infections. However, antibiotics are expensive and cause serious concerns for antibiotic resistance in fish that can be potentially transferred to humans. As an alternative solution, probiotics can be used to prevent infection of pathogenic bacteria in fish. In this work, both bacteria and yeast were isolated from fish gastrointestinal tracts and their inhibitory activity against Nile tilapia pathogenic bacteria was evaluated, as well as other probiotic properties. In this study, 66 bacteria and 176 acid tolerant yeasts were isolated from fish gastrointestinal tracts. Of all isolated microorganisms, 39 bacterial and 15 yeast isolates with inhibitory effect against pathogens were then examined for their probiotic properties (acidic and bile salt resistance, adhesion potential, and biofilm formation), formation of antibacterial factor survival rate under simulated gastrointestinal fluid, and safety evaluation. AT8/5 bacterial isolate demonstrated probiotic properties and the highest inhibition against all 54 tested pathogens while YON3/2 yeast isolate outperformed the inhibitory effect among all yeast isolates. These two probiotic isolates were further identified by 16S rDNA and the D1/D2 domain of 26S rDNA sequence analysis for bacterial and yeast identification, respectively. AT8/5 and YON3/2 showed the highest similarity to Lactiplantibacillus argentoratensis and Candida tropicalis, respectively. This is the first report on isolated L. argentoratensis and C. tropicalis with antipathogenic bacteria of Nile tilapia properties. Collectively, AT8/5 and YON3/2 could be potentially used as promising alternatives to existing antibiotic methods to prevent pathogenic bacteria infection in Nile tilapia farming.
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    Vibration Analysis and Development of a Submersible Ultrasonic Transducer for an Application in the Inhibitory Activity of Pathogenic Bacteria
    (2021-01-01)
    Srathonghuam, Kamonwan
    ;
    Wonganu, Benjamaporn
    ;
    Busayaporn, Wutthikrai
    ;
    Thongsri, Jatuporn
    Development of a new generation of a submersible ultrasonic transducer (SUT) using vibrational analysis aimed for higher efficiency and inhibitory activity of pathogenic bacteria has been presented. The SUT with a dual-stepped shape of front mass and PZT8 transducer working at 50W, 110V, 50 kHz has been examined by the plate counting method. It was found that the SUT could inhibit pathogenic bacteria, e.g., Escherichia coli, Salmonella typhi, Staphylococcus epidermidis, and Staphylococcus aureus. For the vibrational analysis, the results were derived from structural and acoustic simulations using harmonic response analysis (HRA) in ANSYS software. In the structural simulation, the results showed a natural frequency and total deformations both inside and outside of the original SUT corresponding to the results measured by a laser doppler vibrometer. The acoustic simulation, set up as an actual operation at different depths from the water surface, has been applied. The HRA revealed various distributions of acoustic pressure. For further distances away from the SUT, the acoustic pressure decreased. When the SUT has been submerged deeper into the media, the acoustic pressure becomes larger at positions close to the bottom of the tank. This discovery is consistent with power concentration measurement. For the development of the SUT, this research proposed other 5 models as the candidate to be investigated. The results from the acoustic simulation confirmed that the different shapes of the front mass provided different acoustic pressure distributions. The wider head of the front mass in the modified dual-stepped shape generated the highest acoustic pressure and was fully distributed through an all-over cleaning tank. Therefore, this proposed model is suitable for industrial commercialization and possesses the inhibitory activity of pathogenic bacteria.
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