Identification and characterization of actinomycetes antagonistic to pathogenic Vibrio spp. Isolated from shrimp culture pond sediments in thua Thien Hue-Viet Nam

The shrimp diseases in Thua Thien Hue province have mainly accounted for vibriosis caused by Vibrio spp. The addition of substantial amounts of antibiotics is still the method of choice for control the proliferation of pathogenic Vibrio spp. However the abuse of antibiotic agents has led to the emergence of antibiotic-resistant bacteria which may result to resistance transfer to pathogenic bacteria and accumulation of antibiotics in shrimp products. Therefore, developing an alternative strategy to control infections is urgently needed. Following this goal, in the present study, indigenous actinomycetes were isolated from shrimp pond sediments in Thua Thien Hue and strain Al was screened for their activity against two pathogenic strains Vibrio sp. V7 and V10 derived from diseased shrimps from culture ponds in Thua Thien Hue. Based on the cell morphology observed with a JEOL 5410 LV scanning electron microscope and 16S rRNA nucleotide sequence used to search the GenBank database with the BLAST system, strain Al was belong to Streptomyces genus and identified as Streptomyces sp. Al. The 16S rRNA sequence of Streptomyces sp. Al has been deposited in the DDBJ/EMBL/GenBank database with the accession number HM854225. Besides, Streptomyces sp. Al also showed ability to produce siderophore to acquire iron and extracellular enzymes to decompose organic compounds such as starch, protein and cellulose. Otherwise, Streptomyces sp. Al was non-pathogenic to shrimp. Therefore, Streptomyces sp. Al can be considered as not only a candidate for control the shrimp diseases but also a potential probiont for srdimp culture.