Characterization of Vibrio spp. Isolated from Shrimp Pond Water in Hue City, Vietnam

Abstract

This study investigates the characteristics of Vibrio strains isolated from shrimp pond water in Hue City, focusing on their biochemical properties, antibiotic resistance, extracellular enzyme production, hemolytic activity, and toxin-encoding genes. Five Gram-negative, oxidase, and catalase-positive, motile bacterial strains forming colonies on TCBS and CHROMagar™ Vibrio were selected and designated as V06, V16, V17, V25, and V29. Analysis of their 16S rRNA sequences revealed 98.78% to 99.99% similarity with four Vibrio species: V. parahaemolyticus, V. alginolyticus, V. azureus, and V. sinaloensis. All isolates exhibited multidrug resistance to at least four antibiotics. Notably, all strains showed 100% resistance to vancomycin, penicillin, and ampicillin. Hemolytic activity varied among the strains in which V06 displayed beta-hemolysis, V17, and V29 showed alpha-hemolysis, while V16 and V25 exhibited indeterminate hemolytic activity on blood agar. Additionally, all strains demonstrated the ability to produce extracellular proteases and lipases, which have been formerly demonstrated to be related to virulence in Vibrio species. Molecular analysis revealed the presence of toxR and tlh genes in all strains; however, no trh, tdh, pirA, or pirB genes were detected. These findings suggested that the isolated Vibrio strains possessed many virulence-associated traits, including enzyme production, toxR and tlh genes presence, hemolytic activity, and significant antibiotic resistance, which may enhance their pathogenic potential in aquaculture environments.