Isolation, identification and multilocus sequence typing of seven Aeromonas veronii strains

This study characterized Aeromonas veronii isolates recovered from diseased Micropterus salmoides , Procambarus clarkii , and Ctenopharyngodon idella in Guangxi, China. The objective was to assess genetic diversity, virulence gene profiles, and antimicrobial resistance patterns to support effective disease control. Seven strains were confirmed as A. veronii using morphological, physiological, biochemical, and molecular methods. Virulence gene screening showed that all isolates carried GcaT, OmpAI, Hly, Fla, and Exu. Artificial challenge tests demonstrated strong pathogenicity, with median lethal dose (LD₅₀) values ranging from 1.43×10⁶ to 3.58×10⁶ CFU/individual. Antimicrobial susceptibility testing indicated sensitivity to ceftriaxone, cefepime, and fosfomycin, but resistance to amoxicillin, teicoplanin, and sulbactam. Multilocus sequence typing (MLST) identified seven novel sequence types (ST2742, ST2740, ST2765, ST2760, ST2770, ST2774, and ST2775). These results confirm that A. veronii isolates from Guangxi exhibit high genetic diversity, carry multiple virulence genes, and display multidrug resistance. The findings provide a basis for epidemiological surveillance and targeted control of this pathogen.