Genotypic and phenotypic characterization of Edwardsiella isolates from different fish species and geographical areas in Asia: Implications for vaccine development

Abstract

The genus Edwardsiella is one of the major causes of fish diseases globally. Herein, we examined 37 isolates from ten different fish species from India, South Korea and Taiwan to gain insight into their phenotypic and genotypic properties, of which 30 were characterized as E. tarda with phenotypic homology estimated at 85.71% based on API‐20E biochemical tests. Genotyping using 16S rRNA put all isolates together with E. anguillarum, E. hoshinae, E. tarda, E. piscicida and E. ictaluri reference strains in a monophyletic group. In contrast, the gyrB phylogenetic tree clearly separated E. ictaluri, E. tarda and E. hoshinae reference strains from our isolates and put our isolates into two groups with group I being homologous with the E. anguillarum reference strain while group II was homologous with the E. piscicida reference strain. Hence, our findings point to E. piscicida and E. anguillarum as species infecting different fish species in Asia. Homology of the ompW protein suggested that strains with broad protective coverage could be identified as vaccine candidates. This study underscores the importance of combining genotyping with phenotyping for valid species classification. In addition, it accentuates the importance of phylogenetic comparison of bacterial antigens for identification of potential vaccine candidates.

Pathologic changes in cultured Nile tilapia (Oreochromis niloticus) associated with an outbreak of Edwardsiella anguillarum

“…in China (Shao et al, ). Since then, several isolates once identified as E. tarda or E. piscicida have been reassigned to E. anguillarum (Buján et al, ; Dubey et al, ; Shao et al, ). Its presence in the United States has been demonstrated among archived isolates from striped bass ( Morone saxatilis ) dating back to 1994 (Reichley et al, ).…”

“…In conjunction with E. piscicida , E. anguillarum is emerging as a fish pathogen with an expanding host range (Buján et al, ; Dubey et al, ; Griffin et al, ). Information concerning impacts of E. anguillarum infection and its associated histopathologic changes is limited, although several investigations indicate variation in pathogenicity among isolates, as well as differences in virulence among diverse fish species (Abayneh et al, ; Reichley, Ware, Greenway, Wise, & Griffin, ; Reichley et al, ).…”

Application of Outer Membrane Protein-Based Vaccines Against Major Bacterial Fish Pathogens in India

“…It also causes fish gangrene, emphysematous putrefactive disease, red disease, and enteric septicemia in carp, catfish, and several other fish species (32,33). (11,20,21) However, in a recent study, we showed that piscine Edwardsiella isolates from 10 fish species in India belonged to Edwardsiella piscicida and Edwardsiella anguillarum (34). Therefore, it is likely that all fish isolates previously classified as E. tarda were either E. piscicida or E. anguillarum.…”

“…Together with recombinant DNA technology, WGS has contributed to improving OMP vaccine design, while protein sequence comparison has proved to be a powerful tool used to identify immunogenic proteins that are broadly protective against variant pathogen strains. For example, Dubey et al (34) used protein sequence comparison and phylogenetic analysis to show that the OmpW of E. piscicida and E. anguillarum had high similarity, suggesting that a common antigen can be used against isolates from different fish species and geographical areas in Asia.…”

Aeromonas species obtained from different farmed aquatic species in India and Taiwan show high phenotypic relatedness despite species diversity

“…Sequences were used to generate 16S rRNA and gyrB phylogenetic trees in MEGA7 bioinformatics software [ 6 ]. The evolutionary history for each tree was inferred using the Maximum Composite Likelihood method [ 7 ] as described in our previous study [ 8 ]. Genetic distances were computed using Kimura’s two-parameter value [ 7 ].…”