Antimicrobial Resistance and Virulence of Aeromonas Isolates from Endangered Schizothoracinae

Introduction: Emerging pathogenic bacteria represent a growing threat to aquaculture, particularly for rare and protected fish species. Populations of Schizothoracinae have experienced declines due to environmental degradation, habitat loss, and anthropogenic pressures. Despite their ecological and economic importance, microbial threats to these fish remain poorly understood. Understanding the pathogenic potential of bacterial species in Schizothoracinae is essential for developing effective biosecurity measures and conservation strategies. This study aimed to investigate the occurrence, antimicrobial resistance, biofilm-forming capacity, and potential virulence of Aeromonas associated with Schizothoracinae, providing baseline data for disease management and aquaculture safety.

Methods: Aeromonas was isolated from multiple organs of Schizothoracinae and characterized using Gram staining, standard biochemical tests, and molecular identification methods. The isolates were evaluated for antimicrobial susceptibility and biofilm formation, while in silico genomic analyses of related strains were conducted to predict the presence of virulence and resistance genes.

Results: All isolates were confirmed as Aeromonas. They displayed multidrug resistance and variable biofilm-forming ability, with stronger biofilm producers correlating with higher antimicrobial resistance. Genomic analysis suggested the presence of genes linked to virulence and antibiotic resistance, indicating horizontal gene transfer as a likely mechanism driving adaptability and pathogenic potential.

Conclusions: This study provides the first evidence of Aeromonas as a potential pathogen in Schizothoracinae, highlighting its pathogenic and zoonotic potential. The findings emphasize the importance of monitoring microbial threats in protected fish species, supporting aquaculture biosecurity, conservation breeding programs, and future research inclu