Aquaculture and Fisheries (Sep 2024)
Pathogenicity and risk of cross-species transmission of Aerococcus viridans isolated from Tian-e-zhou National Reserve for Lipotes vexillifer in Shishou, China
Abstract
During the survey of potential pathogens in the Tian-e-zhou National Reserve for Lipotes vexillifer in Shishou, China, isolate SS20210504 was isolated from the diseased prey fish-Pelteobagrus fulvidraco and was identified as Aerococcus viridans through 16S rRNA gene, morphological observation, and physiological and biochemical analysis. Artificial infection trials with fish through different methods were conducted. Results indicated that the isolate of SS2021504 caused mortality in fish with the LD50 of 1.0 × 106.2 CFU/mL, 1.0 × 107.9 CFU/mL and 1.0 × 106.8 CFU/mL with the infection method of intraperitoneal injection, co-immersion, and scratch immersion, respectively. Challenged fish exhibited hemorrhages signs similar to naturally diseased fish. Histology analysis showed that the liver and kidney were the principal target organs of isolate SS2021504 in fish, and obvious vacuolation and karyopyknosis occurred in the above organs. To evaluate the pathogenicity of isolate SS20210504 in mice, healthy mice and immunosuppressed mice were further experimentally infected with bacteria, respectively. No death was observed either in healthy mice or in immunocompromised mice. However, the immunocompromised mice inoculated with bacteria showed obvious clinical symptoms and severe damage to multiple organs. The inflammatory signaling pathways were significantly activated with upregulated levels of Myd88, TNFα, AP-1, IL-1β, IL-6, and IFN-γ gene in the spleen from the immunocompromised mice after infected with isolate SS20210504. These findings imply that isolate SS20210504 has the potential risk to YFPs and residents. Continued surveillance of A. viridans and other pathogens in the TZO reserve is suggested to prevent outbreaks in prey fish, YFPs, and residents as well.
