Isolation and identification of Aeromonas salmonicida of bovine origin and its genome-wide and pathogenicity analysis

Aeromonas salmonicida subsp. pectinolytica is a type of bacterium capable of growing at 37 °C, and it was traditionally considered non-pathogenic. In this study, a bacterial strain designated JMAV14 was isolated from the liver tissue of a diseased and deceased bovine in Chaoyang City, Liaoning Province, China. Phylogenetic analysis based on core genome single-copy orthologous genes and whole-genome SNP loci, combined with average nucleotide identity (ANI) analysis, identified JMAV14 at the species level of Aeromonas salmonicida . Further bacteriological identification methods, including VapA gene detection and physiological and biochemical characteristic tests, ultimately classified it as an atypical bovine-derived Aeromonas salmonicida subsp. pectinolytica strain. Pathogenicity assays showed that this strain caused a mortality rate of 70% in mice with a median lethal dose (LD₅₀) of 1.330 × 10 7 CFU per mouse, and a mortality rate of 50% in crucian carp ( Carassius carassius ). These results indicate that JMAV14 possesses strong pathogenicity and broad cross-species infection ability, which challenges the traditional understanding that this subspecies is non-pathogenic. This study clarifies the biological characteristics of bovine-derived Aeromonas salmonicida subsp. pectinolytica during cross-species infection, providing a theoretical basis for the establishment of identification methods, diagnostic techniques, and prevention and control strategies for this bacterium.