Page 40 - 《渔业研究》2026年第3期

第 3 期 戴景辉等： 患病杂交鲟鲟疱疹病毒 3 型与海豚链球菌的共检出、病理特征及药敏分析 333

Co-detection, pathological characteristics, and antimicrobial susceptibility
analysis of acipenserid herpesvirus 3 and Streptococcus iniae in
diseased hybrid sturgeon

DAI Jinghui，LI Chenyang，BAI Lin，LI Mao，YANG Tao *
(Key Laboratory of Aquatic Nutrition and Smart Aquaculture, Ministry of Agriculture Industry and Rural Affairs,
Tongwei Agricultural Development Co., Ltd., Chengdu 610041, China)

Abstract: [Objective] In late July 2025, an outbreak of acute mortality occurred in cultured Siberian hybrid
sturgeon (Acipenser baerii ♀×A. schrenckii ♂) in Ya’an, Sichuan Province, characterized by extensive cu-
taneous and visceral hemorrhages. This study aims to identify the etiological agents and characterize the histo-
pathological lesions to provide a scientific basis for clinical diagnosis and disease control of A. baerii ♀×
A. schrenckii ♂. [Methods] One moribund A. baerii ♀×A. schrenckii ♂ exhibiting typical clinical signs was
randomly collected from each of the six affected ponds (n=6, S1−S6). Tissues from the liver, spleen, kidney,
and brain were sampled for bacterial isolation, viral polymerase chain reaction (PCR) detection, and histopathologi-
cal examination. Molecular biological identification of the isolated strains was performed using 16S rDNA
sequence analysis. Simultaneously, the major capsid protein (MCP) gene of acipenserid herpesvirus 3 (AciHV-3)
was amplified and sequenced for phylogenetic analysis. Antimicrobial susceptibility testing (AST) was conduc-
ted on the recovered bacterial isolates. [Results] Viral detection confirmed that all six samples were positive for
AciHV-3; phylogenetic analysis showed that the MCP gene sequences clustered closely with reference strains
within a single clade. Regarding bacterial isolation, morphologically identical Gram-positive cocci were
recovered from four of the six samples (4/6). The 16S rDNA sequence analysis of the representative strain (Gen-
Bank accession no. PX427207) showed 99% identity with that of Streptococcus iniae in GenBank. In the phylo-
genetic tree constructed based on 16S rDNA sequences, the isolate clustered into a single clade with S. iniae.
Therefore, the isolate was eventually identified as S. iniae. Antimicrobial susceptibility testing revealed signific-
ant variation among the isolated strains. In the eight-antimicrobials susceptibility test, only cefotaxime exhibi-
ted potent inhibitory activity against all isolates. Susceptibility to florfenicol, doxycycline, enrofloxacin, and
ciprofloxacin fluctuated markedly across strains, with the majority being intermediate or resistant. Furthermore,
all isolates demonstrated complete resistance to amoxicillin, sulfamethoxazole/trimethoprim, and neomycin
sulfate, exhibiting a pronounced multidrug resistance (MDR) phenotype. Histopathological analysis revealed ex-
tensive necrosis, hemorrhage, and inflammatory infiltration across multiple organs. [Conclusion] This study
confirms the co-detection of AciHV-3 and S. iniae in cultured sturgeon in Sichuan. Given the severe and con-
sistent histopathological damage, these findings suggest that the high-mortality outbreak was likely driven by
the synergy of AciHV-3 and S. iniae. This research provides essential data for the clinical monitoring and man-
agement of AciHV-3.
Key words: Siberian hybrid sturgeon (Acipenser baerii ♀×A. schrenckii ♂); Streptococcus iniae; acipenserid
herpesvirus 3 (AciHV-3); molecular epidemiology; histopathology