Characterisation of Vibrio spp. isolated from shrimp pond water in Hue City, Vietnam

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. The 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 exhibited 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. The 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 suggest that the isolated Vibrio strains possess numerous virulence-associated traits, including enzyme production, the presence of toxR and tlh genes, hemolytic activity, and significant antibiotic resistance, which may enhance their pathogenic potential in aquaculture environments.