© 2023 Truong Thi Bich Van, et al. This is an open access article distributed under the terms of the Creative Commons Attribution License -NonCommercial- ShareAlike Unported License (http://creativecommons.org/licenses/by-nc-sa/3.0/). Effect of bacteriophages and chamber bitter (Phyllanthus amarus) in combination on Vibrio parahaemolyticus Truong Thi Bich Van 1 *, Do Tan Khang 1 , Le Viet Dung 2 , Le Hoang Bao Ngoc 1 , Nguyen Pham Anh Thi 1 , Tran Thanh Men 3 , Vo Ngoc Tram Anh 1 , Nguyen Kim Thoa 1 1 Institute of Food and Biotechnology Research and Development Institute, Can Tho University, Can Tho, Vietnam. 2 College of Agriculture, Can Tho University, Can Tho, Vietnam. 3 College of Natural Sciences, Can Tho University, Can Tho, Vietnam. ABSTRACT Vibrio parahaemolyticus is one of the causes of acute hepatopancreatic necrosis disease or early mortality syndrome in shrimps. Frequent and repeated application of antibiotics leads to generating resistant strains. Bacteriophages and plant extracts are considered potential biological agents in precaution and treatment of bacterial diseases in aquaculture. The study aimed to investigate the effects of bacteriophages and Phyllanthus amarus extract on strains of V. parahaemolyticus bacteria that were isolated from white leg shrimps (Litopenaeus vannamei). In this study, two strains of V. parahaemolyticus were used: B4XT4 (pure strain) and B4X0T2.2 (isolated strain) for preparing four treatments consisting of combining the bacteria with P. amarus extracts (8 mg/mL), bacteriophage (10 6 PFU/mL), a combination of P. amarus and bacteriophage, and a control treatment. The experiment was conducted in triplicate. The results showed that only plant extracts could inhibit bacterial growth. The colonial morphology of bacteria was changed when bacteriophages and P. amarus extract were added. 1. INTRODUCTION Vibrio parahaemolyticus has been one of the causes of acute hepatopancreatic necrosis disease or early mortality syndrome in shrimps in recent years. Using antibiotics or chemicals to inhibit bacteria has been the most popular course of treatment due to the initial benefits they bring. However, the long-term use of antibiotics leads to antibiotic resistance in bacteria, which is still a challenge in the aquaculture industry and the field of shrimp farming. The research on the inhibition of V. parahaemolyticus using biological therapy is being considered. The method of using phages against aquatic pathogenic bacteria was first used in Japan [1] and quickly became the subject of scientific interest. In recent years, there have been a number of studies using phages in the prevention and treatment of plant and animal diseases [2-4]. Besides, there are also many studies on plant extracts with high antimicrobial efficiency [5], especially Phyllanthus amarus [6,7]. Bacteriophages and P. amarus are considered potential biological agents in the treatment of bacterial diseases in aquatic animals. At present, research and potential applications of these agents in practice are underway, but *Corresponding Author: Truong Thi Bich Van, Institute of Food and Biotechnology Research and Development Institute, Can Tho University, Can Tho, Vietnam. E-mail: ttbvan @ ctu.edu.vn studies in our country that involve their combined use are still limited. Therefore, the study of the ability of the phage in combination with the extract of this plant to inhibit the V. parahaemolyticus bacteria serves as a scientific basis for herbal applications in aquaculture in general and shrimp farming. The objective of this study was to investigate the interaction of phage and P. amarus extract and their effectiveness in inhibiting the spread of the pathogenic V. parahaemolyticus on white leg shrimp. 2. MATERIALS AND METHODS 2.1. Materials All chemicals, equipment, and bacteriophages were supplied by the Molecular Biology Laboratory, Biotechnology Research and Development Institute, Cantho University. The methanolic extract of P. amarus (all the body) was obtained by the College of Natural Sciences, Cantho University. Bacteria strains were isolated from diseased shrimps, pond water, and mud in the Mekong Delta, Viet Nam. 2.2. Isolation of Vibrio spp. Bacteria were isolated from diseased shrimps, pond water, and mud in the Vinh Thuan district, Kien Giang, Bac Lieu Provinces. Diseased shrimps were collected and dissected for hepatopancreas and intestines and were homogenized in a tryptic soy broth (TSB) medium Available online at http://www.jabonline.in DOI: 10.7324/JABB.2023.91082 ARTICLE INFO Article history: Available online: April 04, 2023 Key words: Bacteriophages, Extract, Inhibitory activity, Phyllanthus amarus, Vibrio parahaemolyticus. Received on: September 28, 2022 Accepted on: December 21, 2022 Journal of Applied Biology & Biotechnology Vol. 11(3), pp. 70-76, May-Jun, 2023