In silico characterization of Edwardsiella tarda strain ET-1 isolated from aquarium water reveals zoonotic and pathogenic potential

Edwardsiella tarda is a facultatively anaerobic, Gram-negative bacterium that is widely distributed in aquatic environments. With the increasing interactions between aquatic animals and humans, E. tarda has become an important pathogen with significant implications for global public health. In this study, we characterized strain ET-1, isolated from an aquarium housing Pangasius pangasius, to evaluate its ecological presence, antimicrobial resistance, and pathogenic potential using a combination of phenotypic and genome-based approaches. Biochemical characteristics were determined using the API 20E system. Antimicrobial susceptibility was evaluated using MIC testing to determine resistance to clinically relevant antibiotics. Whole-genome sequencing using Oxford Nanopore Technologies revealed a genome size of 3.76 Mb with a GC content of 57.12%. Genome-based identification using digital DNA–DNA hybridization (dDDH, 86.6%) confirmed the classification as E. tarda. Several virulence-associated genes (flgG – flagellar basal body-rod protein; etfC – electron transfer flavoprotein subunit C) and antimicrobial resistance determinants (qnrS1 – quinolone resistance protein S1; efflux pump genes such as kpnH and kpnF) were identified. Pathogenic potential analysis via PathogenFinder2 indicated a high likelihood of human pathogenicity. Additionally, 16S rRNA-based profiling revealed the widespread environmental and host-associated presence of ET-1-like sequences. These results underscore the zoonotic and environmental significance of E. tarda ET-1 and support its relevance for public health surveillance within the One Health framework.