Isolation, Identification, and Characterisation of a Novel ST2378 Strain from Naturally Diseased Frogs, .

In 2023, exhibiting characteristic skin ulcers were found on a farm in northeastern China. Subsequently, two dominant bacteria, Rd001 and Rd002, were isolated from naturally infected . Experimental infection confirmed that Rd001 was the primary pathogen responsible for the disease in , with a mean lethal dose (LD) of 6.25 × 10 CFU/g. The virulence genotype of Rd001 was identified as +/+/+/+/+/+/+/+/+. Antimicrobial susceptibility testing indicated that Rd001 was sensitive to enrofloxacin, flumequine, and neomycin. MLST analysis showed that Rd001 belonged to a new sequence type of , named ST2378. This study offered the first comprehensive investigation into the pathogenicity, virulence genotypes, antimicrobial resistance, and genetic traits of isolated from , providing a theoretical foundation for preventing and controlling infections.