School of Marine Sciences, Guangxi Laboratory on the Study of Coral Reefs in the South China Sea, Guangxi University, Nanning, China.
Institute of Green and Low Carbon Technology, Guangxi lnstitute of lndustrial Technology, Nanning, China.
J Fish Dis. 2023 Sep;46(9):977-986. doi: 10.1111/jfd.13818. Epub 2023 Jun 9.
Streptococcosis disease caused by Streptococcus agalactiae (Group B Streptococcus, GBS) results in a huge economic loss of tilapia culture. It is urgent to find new antimicrobial agents against streptococcosis. In this study, 20 medicinal plants were evaluated in vitro and in vivo to obtain medicinal plants and potential bioactive compounds against GBS infection. The results showed that the ethanol extracts of 20 medicinal plants had low or no antibacterial properties in vitro, with a minimal inhibitory concentration ≥256 mg/L. Interestingly, in vivo tests showed that 7 medicinal plants could significantly inhibit GBS infection in tilapia, and Sophora flavescens (SF) had the strongest anti-GBS activity in tilapia, reaching 92.68%. SF could significantly reduce the bacterial loads of GBS in different tissues (liver, spleen and brain) of tilapia after treated with different tested concentrations (12.5, 25.0, 50.0 and 100.0 mg/kg) for 24 h. Moreover, 50 mg/kg SF could significantly improve the survival rate of GBS-infected tilapia by inhibiting GBS replication. Furthermore, the expression of antioxidant gene cat, immune-related gene c-type lysozyme and anti-inflammatory cytokine il-10 in liver tissue of GBS-infected tilapia significantly increased after treated with SF for 24 h. Meanwhile, SF significantly reduced the expression of immune-related gene myd88 and pro-inflammatory cytokines il-8 and il-1β in liver tissue of GBS-infected tilapia. The negative and positive models of UPLC-QE-MS, respectively, identified 27 and 57 components of SF. The major components of SF extract in the negative model were α, α-trehalose, DL-malic acid, D- (-)-fructose and xanthohumol, while in the positive model were oxymatrine, formononetin, (-)-maackiain and xanthohumol. Interestingly, oxymatrine and xanthohumol could significantly inhibit GBS infection in tilapia. Taken together, these results suggest that SF can inhibit GBS infection in tilapia, and it has potential for the development of anti-GBS agents.
无乳链球菌（B 群链球菌，GBS）引起的链球菌病导致罗非鱼养殖遭受巨大的经济损失。因此，迫切需要寻找新的抗链球菌药物。本研究评估了 20 种药用植物的体内和体外活性，以获得针对 GBS 感染的药用植物和潜在的生物活性化合物。结果表明，20 种药用植物的乙醇提取物在体外的抑菌活性较低或无，最小抑菌浓度（MIC）≥256mg/L。有趣的是，体内试验表明，7 种药用植物可显著抑制罗非鱼的 GBS 感染，其中苦参（SF）对罗非鱼的抗 GBS 活性最强，达到 92.68%。SF 可显著降低不同浓度（12.5、25.0、50.0 和 100.0mg/kg）处理 24h 后罗非鱼不同组织（肝、脾和脑）中 GBS 的细菌载量。此外，50mg/kg SF 可通过抑制 GBS 复制显著提高 GBS 感染罗非鱼的存活率。此外，SF 处理 24h 后，GBS 感染罗非鱼肝组织中抗氧化基因 cat、免疫相关基因 c 型溶菌酶和抗炎细胞因子 il-10 的表达显著增加。同时，SF 可显著降低 GBS 感染罗非鱼肝组织中免疫相关基因 myd88 和促炎细胞因子 il-8 和 il-1β的表达。UPLC-QE-MS 的正负模式分别鉴定了 SF 的 27 种和 57 种成分。SF 提取物在负模型中的主要成分是α，α-海藻糖、DL-苹果酸、D-（-）-果糖和黄腐醇，而在正模型中主要成分是氧化苦参碱、芒柄花素、（-）马卡因和黄腐醇。有趣的是，氧化苦参碱和黄腐醇可显著抑制罗非鱼的 GBS 感染。综上所述，这些结果表明 SF 可抑制罗非鱼的 GBS 感染，具有开发抗 GBS 药物的潜力。
