Glycyrrhiza extract alleviates hemorrhagic septicemia in Triplophysa yarkandensis infected with Shewanella putrefaciens: integrated bactericidal and immunomodulatory effects.

BACKGROUND: Intensive saline-alkaline aquaculture has made Shewanella putrefaciens a lethal opportunistic pathogen threatening the indigenous economic fish Triplophysa yarkandensis, and antibiotic overuse poses severe ecological risks to this fragile ecosystem. The immune imbalance driving hemorrhagic septicemia progression and the therapeutic potential of herbal immunomodulators, such as Glycyrrhiza extract, in this species remain largely unexplored.

METHODS: We isolated and identified S. putrefaciens as the etiological agent of hemorrhagic septicemia in T. yarkandensis. Using a therapeutic model, we evaluated the efficacy of Glycyrrhiza extract via hematological/serum biochemical analyses, bacterial clearance assays, histopathology, head kidney transcriptomics, and qRT-PCR, alongside appropriate controls.

RESULTS: Glycyrrhiza extract significantly improved the survival of infected fish (58.1% vs. 43.3% in the PBS group), corrected abnormal physiological indices, accelerated bacterial clearance, relieved visceral inflammatory edema, and maintained respiratory and intestinal mucosal integrity. Transcriptomics revealed that it reversed infection-induced transcriptional chaos, with immune signaling and arachidonic acid metabolism as the core regulatory axes. qRT-PCR confirmed that it orchestrated pro-resolution immune responses via rapid acute inflammation activation and sustained anti-inflammatory cytokine upregulation.

CONCLUSION: Glycyrrhiza extract acts as both a bacteriostat and a potent immunomodulator, resolving cytokine storm-induced immunopathology through integrated immune regulation. This offers a sustainable and eco-friendly strategy for managing bacterial diseases in extreme saline-alkaline aquatic environments, supporting its potential as a natural antibiotic alternative in aquaculture.