IN VITRO EVALUATION OF BDELLOVIBRIO SP. AS A BIOCONTROL AGENT AGAINST VIBRIO SP. ISOLATED FROM SHRIMP PONDS

Thu Thi Anh Nguyen¹, Cam Van Hong¹, Cuong Thanh Le²

¹Institute of Biotechnology and Environment, Nha Trang University, No 2 Nguyen Dinh Chieu Street, Nha Trang, Viet Nam

²Institute of Aquaculture, Nha Trang University, No 2 Nguyen Dinh Chieu Street, Nha Trang, Viet Nam

^*Corresponding author: thunta@ntu.edu.vn

The misuse of antibiotics and increasing antimicrobial resistance are major threats, requiring better management strategies for sustainable shrimp farming globally. As a potential alternative for antibiotics, Bdellovibrio-like organisms (BALOs) are the obligate predatory bacteria that capable of attacking and consuming Gram positive and negative bacteria including pathogenic Vibrio species. In this study, we isolated BL5, a strain of BALOs from a cultured shrimp pond in Khanh Hoa province and identified as Bdellovibrio sp. by 16S rRNA sequencing. Using a combination of co-culture agar and broth assays and double layer plates plaque experiments, we indicated that BL5 is able to inhibit the growth of tested pirAB^Vp-bearing V. parahaemolyticus strains isolated from farmed shrimps infected with acute hepatopancreatic necrosis disease (AHPND) at optimal temperature of 25^oC – 30^oC and at optimal pH of 7.5 – 8.2. In addition, BL5 also exhibited a certain lysis effect on the selected 18 strains of Vibrio sp. including V. harveyi, V. parahaemolyticus, V. alginolyticus, V. owenssi and V. vulniticus. These results suggest that it may be possible to use the isolated Bdellovibrio sp, BL5 in controlling pathogenic Vibrio sp. in aquaculture.

Keywords: Bdellovibrio-like organisms (BALOs), Vibrio, antibiotic, shrimp, AHPND

FEED UTILIZATION, CELLULAR IMMUNITY, AND RESISTANCE AGAINST STREPTOCOCCUS AGALACTIAE OF NILE TILAPIA (OREOCHROMIS NILOTICUS) AS ENHANCED BY DIETARY SUPPLEMENTATION OF LACTOBACILLUS PLANTARUM L03

Thi Mai Nguyen¹, Ngoc Anh Do Thi¹, Xuan Chinh Le¹, Md. Sakhawat Hossain², Thanh Huong Vu Thi³, and Nang Thu Tran Thi¹*

¹ Faculty of Fisheries, Vietnam National University of Agriculture, Hanoi, Vietnam;

²  Department of Aquaculture, Faculty of Fisheries, Sylhet Agricultural University, Sylhet-3100, Bangladesh;

³  Faculty of Aquaculture, Ha Long University, Quang Ninh, Vietnam;

^*Corresponding author: Assoc.Prof. Nang Thu Tran Thi, trannangthu@vnua.edu.vn

This study aimed to evaluate the effect of dietary Lactobacillus plantarum on growth and disease resistance in Nile tilapia. L.plantarum were supplemented in feed at 0, 2, 5, 10 g/kg corresponding to LP0, LP2, LP5, LP10 groups. Fish (19.07±0.43 g) were fed on the experimental feed for seven weeks. After feeding trial, fish were infected with Streptococcus algalactiae at 5×10⁵ CFU/mL and monitored for 14 days. The blood samples were collected for hematological analyses after feeding trial and bacterial challenge. Results showed no significant effect of dietary L.plantarum on fish growth while the positive effects were found in LP2 and LP5-fed fish for feed utilization. The higher values of hematological variables were observed in LP5-fed fish after bacterial challenge and the lowest cumulative mortality was also recorded in this group. Globally, the supplementation of L.plantarum L03 at 5 g/kg diet enhanced feed utilization, cellular immunity, and disease resistance in tilapia.

Keywords: Probiotics, feed utilization, hematological parameter, disease resistance

DEREPLICATION  OF ANTIVIBRIO COMPOUNDS NOCARDIOPSIS SPP.

AND IN SILICO ANALYSIS TARGETING  LUXT OF VIBRIO PARAHAEMOLYTICUS

Noer Kasanah^1*, Maria Ulfah ², David C. Rowley^3,*

¹Department of Fisheries, Faculty of Agriculture, Universitas Gadjah Mada, Yogyakarta, Indonesia

²Biotechnology, The Graduate School of Universitas Gadjah Mada, Yogyakarta, Indonesia

³Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, USA

^*Corresponding author: noer.kasanah@ugm.ac.id

Vibriosis is one of major infectious diseases caused by Vibrio spp and generate economic loss in aquaculture. Resistance to antibiotics and increasing incidence vibriosis due to climate change has driven to seek for new antivibrio. Quorum-sensing (QS) is one of the targets to discover antivibrio. The objectives of this study are to identify bioactives compounds from Nocardiopsis spp. trough dereplication and analyze compound trough in silico targeting QS transcription regulator LuxT of V. parahaemolyticus. Metabolites were analyzed using liquid chromatography-mass spectrometry (LC-MS). Dereplication of compounds was conducted based on databases MarinLit. Antivibrio was tested using resazurin microtiter assay. Autodock Tools and Autodock Vina were used as molecular docking tools. Extract dereplication revealed the production of 18 known compounds and 2 unknown hits that potentially new. All isolates produced antivibrio against Vibrio parahaemolyticus and V. alginolyticus with MICs value between 0.625 and 5 µg/µl. In silico analysis with LuxT revealed that the anti-QS mediated anti-infection activity of Nocardiopsis against V. parahaemolyticus infection is accomplished by the presence of active metabolites Nocapyrone M. Hence, we suggest that active metabolites could be the new alternative agents to control V. parahaemolyticus. This study reported that Nocardiopsis spp. are great resources for antivibrio discovery.

Keywords: Vibriosis, Vibrio parahaemolyticus, Nocardiopsis, LuxT, Nocapyrone M