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Safety and Efficacy of Vaccine Han-Streptila in Commercial Tilapia

Ho Thu Thuy, Nguyen Huu Vu, Tran Thi Khanh Chi, Vu Duc Hanh, Nguyen Viet Khong, LaiThi Lan Huong

Received: 01-10-2018 / Accepted: 14-04-2019
The objective of the present study was to determine the safety and efficacy of vaccine Han-Streptila incommercialtilapia by injection (in Hau Giang, Tien Giang and Dong Thap provinces) and by oral route (in An Giang, Vinh Long and Dong Thap provinces). The control, immune and safe groupswere set up in each province. The safety of the vaccine was determined by observing the abnormalities of experimental fish; the efficacy of the vaccine was determined by comparing the final cumulative mortality between thevaccinated groupandthe control group during the trial or after challenge test. This also was evaluated throughrelative percentage survival(RPS).The results showed that the vaccine hadno effect on mortality and growth of fish. Thevaccineefficacy through injection with tilapia of 10g/p achieved 66.9% and oral route for fish 2.5g/p achieved 63.9% protection after 24 weeks. Therefore,HAN-STREPTILA vaccine tested in the South of Vietnam wassafe and highly effective.
Detection of Salmonella typhimuriumCausing Salmonellosisin Layer Ducks Raised in Phung Thuong Commune, Phuc Tho, Hanoi

Truong Ha Thai, Chu Thi Thanh Huong, Vu Thi Thu Tra, Cam Thi Thu Ha, Truong Lan Oanh

Received: 15-03-2023 / Accepted: 05-01-2024
The purpose of this study was to identify Salmonella typhimurium (S.typhimurium), causing salmonellosis in layer ducks farmed in Phung Thuong commune, Phuc Tho, Ha Noi. A total of 32 farm households were selected based on farm-scale and breeding method. Forty-four salmonelosis-suspected ducks were necropsied to monitor gross lessions; of which, 33 ducks had gross lessions of the disease. We collected livers (15 samples), spleens(11 samples), and ovary (7 samples) from 33 ducks with gross lession of the disease, besides, irregular egg yolks (15) were collected for bacteria isolation and then typing by PCRmethod. Results indicated that liver samples had the highest percentage of positive samples (60.0%), followed by spleen (54.5%), ovary (42.9%) and the lowest was the irregular egg yolk sample (40.0%). Twenty-four S.typhimurium strains were isolated and detected by PCR method. Testing the antibiotic sensitivity of the S.typhimurium isolates showed that thesestrains were most susceptible to colistin(100%), followed by doxycycline (79.2%) and gentamicin (70.8%) but moderately sensitvie or resistant to amoxicillin, ampicillinand neomycin.
Evaluating Bactericidal Effect and Therapeutic Efficacy of Amoxicillin and Amoxicillin Combined with Clavulanic Acid on Streptococcus agalactiae Isolated from Diseased Tilapia

Truong Dinh Hoai, Tran Thi Diem Quynh, Dang Thi Hoa, Do Dinh Hung, Vo Van Viet, Nguyen Duc Chinh, Nguyen Thi Huong Giang, Doan Thi Nhinh, Ngo Phu Thoa, Kim Van Van

Received: 25-10-2023 / Accepted: 05-01-2024
The study evaluated and compared the bactericidal effect and treatment of the disease of tilapia caused by Streptococcus agalactiae with amoxicillin and amoxicillin combined with clavulanic acid. To conduct a study, 4 isolates of S. agalactiae isolated from diseased tilapia were selected for identification by biochemical methods and PCR assay. The inhibition ability of antibiotics was evaluated through the diffusion method on agar plate and the minimum inhibitory concentration (MIC). The treatment efficacy was evaluated 14 days post challenge. The results showed that amoxicillin combined with clavulanic acid revealed bigger inhibition zones. The minimum inhibitory concentration of amoxicillin was 2 µg/ml compared to that of only 0.25 µg/ml of amoxicillin and clavulanic acid. The results of treatment experiments showed that amoxicillin combined with clavulanic acid could yielded higher treatment efficacy (91.1%) than those treated with amoxicillin alone (77.8%). This is the first study to compare and evaluate the inhibitory and therapeutic efficacy of amoxicillin with and without clavulanic acid on pathogenic bacteria in aquaculture.
Biofilm Forming and Antibiotic Resistance of Biofilm Producing Staphylococcusspp.

Nguyen Van Giap, Cao Thi Bich Phuong

Received: 01-10-2018 / Accepted: 07-11-2018
This study was conducted to determine the biofilm formation and antibiotic resistance of the biofilm-forming Staphylococcusspp. By the application of microtiter plate test, a quantitative method, the biofilm formation of staphylococci was determined. It was found that 51.61% strains produced biofilms at strong, medium and weak levels. Study on the production of biofilm over time showed that the biofilm formation by staphylococci increased from 4 hours to 20 hours, and then decreased from 24 hours to 40 hours post innoculation in 96-wells plate. In terms of antibiotic resistance, the biofilm producing strains were able to survive under the concentrations of antibiotics of 10 to 100 times higher than the planktonic bacteria.
Antibiotic Resistance Profile and Molecular Characterizatin ofExtended Spectrumβ-lactamase (ESBL) - Producing Escherichia coli Isolated from Ducks

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

Received: 19-03-2024 / Accepted: 12-04-2024
This study aimed to determine the phenotypic and genotypic antibiotic resistance profile of ESBL-producing E. coliisolated from ducks. A total of 50 rectal swab samples from ducks were collected at markets in Gia Lam district, Hanoi city. The isolates in this study were all resistant to streptomycin, ampicillin, tetracycline, ceftazidime and cefotaxime. Besides, they also exhibited high resistance rates to sulfamethoxazole/trimethoprim (95.65%), gentamicin (91.3%)and chloramphenicol (91.3%). The lowest resistance rate was recorded with cefoxitin (30.43%) and 100% isolates were susceptible to meropenem. Interestingly, all of these isolates were determined as multidrug resistant strains. The result of phenotypic detection of ESBL indicated that 100% (20/20) presumptive ESBL producing E. colistrains were able to produce ESBL Among them, 50% (10/20) isolates carried blaTEM gene,25% (5/20) haboured blaCTX-M-1, 10% (2/20) habour blaCTX-M-9, and 15% (3/20) carried both blaCTX-M-1 and blaTEMsimultaneously.
Purification and Characterization of Cellulase from Bacillussp. M5Strain

Trinh Thi Thu Thuy, Nguyen Thi Thanh Thuy, Nguyen Thi Lam Doan, Hoang Thi Ngoc

Received: 20-06-2018 / Accepted: 28-11-2018
The objective of the present study was to purify and determine the properties (optimal temperature, heat stability, optimal pH, pH stability, effects of metal ions) of cellulase derived from Bacillussp. M5strain. The crude enzyme produced from the culture of cellulase-producing bacillus M5 strain was collected by centrifugationand precipitated for purification andcharacterization. To investigate the enzyme's characteristics onoptimal temperature, pH as well as heat stability, pH stability and the effect of certain metal ions, the enzyme fluid was treated under different conditions. The enzymewas disolvedin acetate buffer pH 5.50 mM to determine enzyme activity. Results showed that the cellulase from Bacillus M5 strain was active at an optimaltemperature of 65C; optimalpH of 5.5; heat stability at about 50C (activity remains53% after 120 minutes); pH of 6.0 to 6.5.Ca2+and Mg2+metal ions increasedenzyme activity and Zn2+ion decreasedenzyme activity. The enzyme hadthemolecular weight of 45 kDa.
Evaluation of Quorum Sensing Communication between Pathogenic Bactria Causing Acute Hepatopancreatic Necrosis Disease and Vibrio Alginolyticus

Tran Thi Thuy Ha, Nguyen Thi Hanh, Pham The Viet, Phan Thi Van, Truong Thi My Hanh

Received: 01-08-2018 / Accepted: 26-08-2018
Bacterial cell-to-cell communication(quorum sensing - QS) is associated with the virulence of pathogenic bacteria. The study was conducted to evaluatethe QS communication between Vibrioparahaemolyticus - pathogenic agent causing acute hepatopancreatic necrosis disease (AHPND) and V. alginolyticus- non-AHPND and, concurrently, to determine the role of cinnamon essential oil for QS between two bacterial species mentioned above. The methods used included traditional bacterial culture and PCR technique. Results showed that V. alginolyticus received virulence gene AHPND from V. parahaemolyticusunder the culture condition with three times of heat shock at 400C (5 min) and 700C (2 min) via QS mechanism. In addition, cinnamon essential oil with a dose of 0.1μL/600μL disrupted the QS communication system of bacteria, causing V. alginolyticusimpossible to receive virulence gene causing AHPND from V. parahaemolyticus.
Establishment of ASimple and Efficient Transformation Protocol for Hairy Root Induction of Wild Bitter Melon (Momordica charantia L.var. abbreviata Ser.)

Nguyen Thi Thu Trang, Vu Thi Dao, Bui Minh Tri

Received: 28-09-2016 / Accepted: 13-02-2017
Wild bitter melon (Momordica charantia L. var. abbreviata Ser.) is known as a valuable vegetable and herb. It contains several important bioactive substances, including glycoside, saponin, alkaloide, triterpen and steroide. This study was carried out to establish a simple and efficient transformation protocol for inducting hairy roots of wild bitter melon by using strain TR7 of Agrobacterium rhizogenes which carries pPE113 binary vector harbouring e-gfp gene. Major parameters were optimized including, the age of plant and position for injection. The results indicated that highest hairy root induction frequencies was about 69.66-73.33% when seven-day-old seedlings were used to infect with the bacterium using hypocotyl. After regeneration and selection, thirty putative root clones of 4 specific phenotypes, i.e. white hairs, fast growth and branching on hormone-free MS medium, were obtained. The average GFP expression rate in 4 specific phenotypic groups were about 46.7%. PCR analysis using specific primers for rolA gene and virD gene confirmed the presence of the rolA gene and absence of virD gene in the genome of four hairy root lines. It was suggested that this simple transformation protocol can be applied for hairy root induction of other varieties as well.

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