Xin Jige, Pu Qiqi, Wang Ruiying, Gu Yeqing, He Lin, Du Xuan, Tang Guowen, Han Diangang
College of Veterinary Medicine, Yunnan Agricultural University, Kunming, China.
College of Plant Protection, Yunnan Agricultural University, Kunming, China.
Front Vet Sci. 2024 Jun 14;11:1408376. doi: 10.3389/fvets.2024.1408376. eCollection 2024.
(), also known as group B (GBS), is a highly infectious pathogen. Prolonged antibiotic usage leads to significant issues of antibiotic residue and resistance. Chelerythrine (CHE) is a naturally occurring benzophenidine alkaloid and chelerythrine chloride (CHEC) is its hydrochloride form with diverse biological and pharmacological activities. However, the antibacterial mechanism of CHEC against GBS remains unclear. Thus, this study aims to investigate the antibacterial activity of CHEC on GBS and elucidate its underlying mechanism. The antibacterial effect of CHEC on GBS was assessed using inhibitory zone, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) assays, as well as by constructing a time-kill curve. The antibacterial mechanism of CHEC was investigated through techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM), measurement of alkaline phosphatase (AKP) activity, determination of Na K, Ca Mg-adenosine triphosphate (ATP) activity, observation of membrane permeability, and analysis of intracellular reactive oxygen species (ROS) and mRNA expression levels of key virulence genes. The results demonstrated that the inhibition zone diameters of CHEC against GBS were 14.32 mm, 12.67 mm, and 10.76 mm at concentrations of 2 mg/mL, 1 mg/mL, and 0.5 mg/mL, respectively. The MIC and MBC values were determined as 256 μg/mL and 512 μg/mL correspondingly. In the time-kill curve, 8 × MIC, 4 × MIC and 2 × MIC CHEC could completely kill GBS within 24 h. SEM and TEM analyses revealed significant morphological alterations in GBS cells treated with CHEC including shrinkage, collapse, and leakage of cellular fluids. Furthermore, the antibacterial mechanism underlying CHEC's efficacy against GBS was attributed to its disruption of cell wall integrity as well as membrane permeability resulting in extracellular release of intracellular ATP, AKP, Na K, Ca Mg. Additionally CHEC could increase the ROS production leading to oxidative damage and downregulating mRNA expression levels of key virulence genes in GBS cells. In conclusion, CHEC holds potential as an antimicrobial agent against GBS and further investigations are necessary to elucidate additional molecular mechanisms.
无乳链球菌（GBS），也被称为B族链球菌，是一种高传染性病原体。长期使用抗生素会导致严重的抗生素残留和耐药性问题。白屈菜红碱（CHE）是一种天然存在的苯并菲啶生物碱，氯化白屈菜红碱（CHEC）是其盐酸盐形式，具有多种生物学和药理活性。然而，CHEC对GBS的抗菌机制尚不清楚。因此，本研究旨在探讨CHEC对GBS的抗菌活性并阐明其潜在机制。通过抑菌圈、最低抑菌浓度（MIC）、最低杀菌浓度（MBC）测定以及构建时间 - 杀菌曲线来评估CHEC对GBS的抗菌效果。通过扫描电子显微镜（SEM）、透射电子显微镜（TEM）、碱性磷酸酶（AKP）活性测定、钠钾、钙镁 - 三磷酸腺苷（ATP）活性测定、膜通透性观察以及细胞内活性氧（ROS）和关键毒力基因mRNA表达水平分析等技术来研究CHEC的抗菌机制。结果表明，CHEC在浓度为2mg/mL、1mg/mL和0.5mg/mL时，对GBS的抑菌圈直径分别为14.32mm、12.67mm和10.76mm。MIC和MBC值分别确定为256μg/mL和512μg/mL。在时间 - 杀菌曲线中，8×MIC、4×MIC和2×MIC的CHEC可在24小时内完全杀灭GBS。SEM和TEM分析显示，用CHEC处理的GBS细胞出现明显的形态改变，包括细胞收缩、塌陷和细胞液泄漏。此外，CHEC对GBS有效抗菌的机制归因于其破坏细胞壁完整性以及膜通透性，导致细胞内ATP、AKP、钠钾、钙镁释放到细胞外。此外，CHEC可增加ROS产生，导致氧化损伤并下调GBS细胞中关键毒力基因的mRNA表达水平。总之，CHEC作为一种抗GBS的抗菌剂具有潜力，需要进一步研究以阐明其他分子机制。
