Isolation and Selection of Actinobacteria Against Pathogenic Bacteria From Shrimp Pond Water on Duyen Hai District, Tra Vinh Province, Vietnam
Abstract
In the shrimp-farming process at Vietnam has used antibiotic mostly, this leads status of antibiotic resistant bacteria and product do not qualified to the market. Bacteria, especially actinobacteria, had resistant ability to human pathogenic bacteria in water and they have an important role in sustainable aquaculture. This study aimed to isolate and select good actinobacterial strains against pathogenic bacteria, from 8 samples of shrimp-pond water at 3 sites Ngu Lac, Phuoc Tri and Long Toan of Duyen Hai district, Tra Vinh province on Gause-1 agar medium. Fifty-three actinobacterial isolates were isolated in which 23 isolates resistant to at least one of pathogenic bacteria by well-diffusion method. Among them, 15 isolates were identified as resistant to Bacillus cereus, 12 to Staphylococcus aureus, 11 to Escherichia coli and 18 to Vibrio parahaemolyticus. There were 7 isolates had good resistance to select for PCR technique and sequencing and the result were determined 7 these strains: NL1-1.9, NL1-18a, NL2-2.1b1, NL2-2.2, PT1-1.7a, PT2-2.8a, LT1-1.3 belonged to three genere: Streptomyces, Nocardioides, and Glutamicibacter.
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Introduction
Vietnam has a suitable location and condition for fishery and aquaculture with shoreline length 3,260 km, together with abundant river canal system, Aquaculture is one an important export of agricultural production among shrimp cultivation jas large contribution in general report of Vietnam agriculture. Shrimp cultivation has been faced with pathogenic bacterial infections, such as luminous vibriosis and acute hepatopancreatic necrosis disease (AHPND) caused by Vibrio harveyi and Vibrio parahaemolyticus, respectively [1]. Shrimp production in Southeast Asia steadily averaged 6.0% annual growth from 2008 to 2011; however, the production declined from 3.45 million metric tons (MMT) to 3.25 MMT in 2012 (down 5.8%) and to 3.21 MMT in 2013 (down 1.1%) due to the impact of early mortality syndrome (EMS) in China, Thailand, Vietnam and Malaysia [2]. To solve these problems, shrimp farmers normally use antibiotics to eliminate the pathogenic bacteria; however, antibiotics can be harmful to consumer health. In addition, long term use of antibiotics leads to residual compounds in sediment and water, and the bacteria can adapt themselves by selection for antibiotic resistant genes [3]. For sustainable shrimp cultivation, probiotics and/or their anti-vibrio compounds as biocontrol agents have been explored to control vibriosis in shrimp farming. Gram-positive actinobacteria have been identified as potential probiotics for aquaculture, with effects against various pathogens [4]. The objective of this work was to isolate and select together with identify bacterial isolates having good resistance to V. parahaemolyticus and human pathogenic bacteria in water of shrimp ponds on Duyen Hai district, Tra Vinh province, Vietnam in order to product a probiotic for shrimp cultivation sustainably.
Conclusion
Fifty-three actinobacteria isolates isolated from 8 water samples of 3 sites of schrimp-pomfs, identying 17 isolates produce antimicrobial active metabolites inhibiting positiva-gram bacteria and negative-gram bacteria. Seven actinobacteria strains as: NL1-1.9, NL1-18a, NL2-2.1b1, NL2-2.2, PT1-1.7a, PT2-2.8a, LT1-1.1 belonged to 3 genera: Streptomyces, Nocardioides and Glutamicibacter.
