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• Isolation and Rapid Identification by MALDI-TOF MS of Riemerella anatipestiferfrom Clinical Cases in Waterfowls in Ha Nam Province

  Truong Quang Lam, Nguyen Thi Lan, Nguyen Thi Thu Huong, Dao Le Anh, Tran Danh Son

  Date Received: 01-06-2021 / Date Accepted: 10-01-2022

   Abstract PDF (VIETNAMESE)

  This study aimed to isolate and identify by PCR and MALDI-TOF MS of Riemerella anatipestifer(RA) strains isolated from ducks and muscovy ducks in Ha Nam province. Samples including brain, heart, liver, lung, and spleen were collected from 45 suspected ducks in the farms in Ly Nhan, Binh Luc, Duy Tien districts. Total 27 out of 45 ducks showed the appearance of suspected colonies with the following characteristics: small, transparent, non-hemolysis with the main biochemical features as negative for indole, positive for catalase and oxidase test, and did not grow on MacConkey agar plates. Rapid identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) showed that 27 suspected colonies were positive to RA. This result is 100% in agreement with the PCR results.

• Isolation and Selection of Bacillus amyloliquefaciens Strains Antagonistic Against Salmonella gallinarum

  Hoang Minh Duc, Nguyen Thi Thu Hang, Nguyen Thi Lan, Cam Thi Thu Ha, Tran Thi Khanh Hoa, Pham Thuy Linh, Hoang Minh Son

  Date Received: 01-01-2026 / Date Accepted: 30-12-2025 / Date Published: 23-01-2026

   Abstract PDF (VIETNAMESE)

  Probiotics are one of the most popular alternatives to antibiotics for disease prevention and growth promotion in livestock. Bacillus amyloliquefaciens (B. amyloliquefaciens) possesses several characteristics suitable for probiotics, including resistance to high temperatures, low pH, bile salts, and antagonism against pathogens. This study was conducted to isolate and select B. amyloliquefaciens strains antagonistic against Salmonella gallinarum (S. gallinarum), which causes Salmonellosis. The result showed that four B. amyloliquefaciens strains were isolated and identified from 100 fresh fecal samples of healthy chickens using the culture methods and Matrix-Assisted Laser Desorption/Ionization - Time-of-Flight (MALDI-TOF) technology. The isolates were not hemolytic on blood agar and exhibited high stability in adverse conditions (pH 3.0 and 0.3% bile salt), with a survival rate greater than 80%. The results of the antimicrobial susceptibility test revealed that all 4/4 (100%) of the B. amyloliquefaciens isolates were resistant to tetracycline and 3/4 (75%) were resistant to erythromycin. The isolates also exhibited strong antagonism against S. gallinarum in vitro, producing inhibition zones with diameters greater > 16 mm.

  DOI: https://doi.org/10.31817/tckhnnvn.2026.24.1.07

• Isolation and selection of lactic acid bacteria antagonistic to common pathogenic bacteria in livestocks

  Nguyen Van Thang, Pham Thuy Linh, Hoang Minh Duc, Tran Thi Khanh Hoa, Nguyen Thi Lan, Cam Thị Thu Hà, Hoang Minh Son

  Date Received: 24-11-2024 / Date Accepted: 18-04-2025 / Date Published: 30-04-2025

   Abstract PDF (VIETNAMESE)

  Probiotics are known as a promising alternative to antibiotics in improving productivity and controlling infectious diseases in livestocks. The study was conducted to isolate lactic acid bacteria (LAB) with strong antagonism against some common pathogenic bacteria in livestocks. A total of 33 LAB strains were isolated from 100 chicken intestine and pork intestine samples. Among them, 5 isolates showing strong antagonistic activity against 5 pathogenic bacteria tested (S. Typhimurium, S. Gallinarum, E. coli K88, S. aureus, and C. perfringens) were identified as Pediococcus pentosaceus, Levilactobacillus brevis, Lactiplantibacillus plantarum using MALDI TOF. The LAB isolates in this study were non-hemolytic, negative for DNase production, and highly resistant to acid and bile salt. The auto-aggregation rates of the LAB isolates were all over 40% and the rates of co-aggregation of them to the pathogens ranged from 24.39% to 45.17%. In particular, all LAB isolates were determined as multi-resistant strains, with the highest resistant rates to ampicillin, erythromycin, and tetracycline. Overall, the 5 selected LAB isolates are potential strains for the production of probiotics preventing animal diseases.

  DOI: https://doi.org/10.31817/tckhnnvn.2025.23.4.03

• Isolation and Selection of Lactic Acid Bacteria for use in Soy Yogurt Production

  Tran Thi Dinh, Than Thi Huong, Nguyen Thi Hoang Lan, Le Minh Nguyet, Dang Thu Huong, Nguyen Thi Minh

  Date Received: 10-05-2023 / Date Accepted: 05-10-2023

   Abstract PDF (VIETNAMESE)

  This study was conducted to isolate and select potential lactic acid bacteria for soy yogurt production. From 17 natural fermentation samples, 51 lactic acid strains capable of fermenting soy milk into soy yogurt were isolated. Based on the quality analysis of soy yogurt, 10 strains were selected. Using MALDI-TOF/MS technique, these 10 strains were classified into 3 species: Enterococcus faecium, Lactococcus lactis, andStreptococcus equinus. Among them, Lactococcus lactisK1 was evaluated as the best strain for soymilk fermentation due to its outstanding characteristics such as high growth rate, biological safety, and production of high-quality yogurt, especially with the ability to produce a high amount of exopolysaccharide (1,381.7 mg/kg). The soy yogurt initially received positive responses from consumers.

• Isolation and Selection of Lactic Acid Bacteria for Probiotic Beverage Production from Ginger

  Vu Quynh Huong, Vu Thi Yen, Nguyen Thi Thanh Thuy

  Date Received: 28-09-2022 / Date Accepted: 20-12-2022

   Abstract PDF (VIETNAMESE)

  Lactic acid bacteria play an important role in the production of fermentedfoods. This study aimed to isolate and select lactic acid bacteria strains from fermented products for application in the production of ginger-based probiotic drinks. Fourty sixstrains of bacteria were isolated. The isolates producedcolonies with 1.0 to 1.5mm in diameter, mainly round, glossy, milky white, and floating pellicle in liquid culture. Six gram-positive, catalase-negativestrains withrod orspherical shaped cellswere pre-selected. Identification by MALDI-TOF revealedthat theybelongto 4 speciesof Enterococcus faecium, Enterococcus casseliflavus, Lactobacillus fermentumand Lactobacillus plantarum. Furtherstudy was conducted for the strain L.plantarumSM1.3. Itwas tolerantto acid(pH 1.0-3.0)and 0.3%bile salts,and ableto produce amylase, protease, and cellulase. This strain inhibited two tested bacteria,E. coliand Salmonellasp.Gene alignment results indicated that the strain SM1.2 belongedto Limosilactobacillus fermentumspecies and strain SM1.3 namedLactiplantibacillus plantarum.Ginger-based probiotic drink usingL. plantarumSM1.3 has good sensory quality andbacterial density and can be stored up to 5 days at 4C.