Molecular Characteristics Demonstrate the Occurrence of Phylogenetic Similar Isolates of Vibrio alginolyticus and Vibrio parahaemolyticus in Aquatic Environments

Phylogenetic analysis of Vibrio alginolyticus and V. parahaemolyticus from aquatic sources

Abstract

Vibrio alginolyticus is an opportunistic fish pathogen with a potential to cause septicemia and often associated with other Vibrio infections, particularly Vibrio parahaemolyticus, and can pose a significant threat to aquatic health. This study investigated the biochemical and phylogenetic characteristics of V. alginolyticus isolated from various aquaculture farms, focusing on its prevalence, hemolysin genes, genetic relatedness, and antibiotic susceptibility. Out of 92 brackish water aquaculture farm samples, 16 isolates were biochemically confirmed as V. alginolyticus, with 12 subsequently confirmed by polymerase chain reaction targeting collagenase gene. Molecular analysis of the thermolabile hemolysin gene (tlh) via specific PCR amplified a 450 bp fragment in 8 isolates, confirming the presence of the tlh gene. Pulsed Field Gel Electrophoresis (PFGE) typing differentiated tlh-positive and tlh-negative V. alginolyticus isolates with 92% genetic similarity. The isolates exhibited proteolytic, lipolytic, and lecithinase activities. Notably, the isolates showed intermediate resistance to most of the tested antibiotics, indicating exposure to antimicrobial agents. This study provides evidence of the presence of similar phylogenetical isolates of V. alginolyticus and V. parahaemolyticus in aquatic environments. Furthermore, this study emphasizes the importance of expanding surveillance programs by incorporating strain-specific characterization to better understand
 and control vibriosis in aquaculture.