EAGER: Antibacterial clay effects on pathogenic biofilms

这位研究人员最近对杀死人类病原体的粘土进行了研究，包括耐甲氧西林金黄色葡萄球菌(MRSA)等耐抗生素菌株，证明了它们的共同特征。在世界范围内，到目前为止，只有5%-10%的粘土在水合和体外测试时是抗菌的。大多数抗菌粘土来自热液蚀变的火山岩，火山成因的流体产生含有还原金属的矿物。铁质伊利-蒙皂石(I-S)是最常见的粘土矿物，但也有部分样品以高岭石为主。抗菌粘土矿物组合也可能含有非粘土还原的铁矿物(例如，黄铁矿)，这些矿物会被氧化，对细胞膜和细胞内蛋白质造成损害。关键是粘土矿物组合将水合水缓冲到pH和Eh条件下，这些条件会释放对抗菌过程至关重要的金属，允许与细菌相互作用。抗菌粘土还会与细菌膜交换结构离子，从而削弱细菌的防御能力。这项研究将通过测试它们对生物膜的影响，将这种对抗菌过程的新理解提升到一个新的水平。人类的传染病通常会形成生物膜，这是一种细菌群落，比测试的“自由漂浮”细菌悬浮液对抗生素更具抗药性。抗菌粘土对生物膜的有效性是支持动物试验中昂贵的杀菌效果测试的重要一步。如果抗菌粘土对生物被膜有效，体内试验可能导致设计新的抗药性细菌治疗方法，潜在应用于伤口敷料、医疗植入物(关节置换、导管)、动物饲料、农业病原体和抗菌建筑材料的生产。这项研究的科学目标是记录一种以前针对广泛的浮游人类病原体进行测试的抗菌粘土对最常见的感染性疾病的生物膜的影响。研究人员将与梅奥诊所(明尼苏达州罗切斯特市)的传染病研究人员合作，开发将粘土应用于生物膜的方案，并评估导致或限制其抗菌活性的条件。将对常见和抗药性细菌菌株的临床分离进行测试。研究人员已经证明，抗菌粘土释放的金属(铝、铁)共同作用，破坏细胞膜和细胞内蛋白质，因此它们将监测这些金属与生物膜的相互作用。测试抗生素的标准方法必须修改为测试天然粘土，因为矿物质在释放金属的同时不会完全溶解，因此会影响细菌生存的光谱评估。此外，研究人员发现，各种生长介质中的金属形态通过限制金属与细菌的反应来影响结果。因此，生长在特氟龙圆盘上的健康生物膜将与粘土悬浮液一起培养，培养物将通过连续稀释和平板计数来评估其活性。如果成功，该项目将弥合矿物学和医学之间的差距，促进粘土或其衍生物在抗生素耐药性感染中的应用。这将促进评估改善人类健康的矿物质的医学方案的开发。对社会的最终好处将是建立一种经济、安全的天然矿物疗法来治疗抗生素耐药性感染。抗菌活性和应用于伤口护理的安全性的证据可能导致粘土用于治疗伤口的经济用途，或开发包含类似抗菌特性的新药。

Recent research by the investigator on clays that kill human pathogens, including antibiotic resistant strains like methicillin resistant S. aureus (MRSA), has documented their common characteristics. Worldwide, only 5-10 % of clays studied to date are antibacterial when hydrated and tested in vitro. Most antibacterial clays are from hydrothermally altered volcanics, where volcanogenic fluids produce minerals containing reduced metals. Ferruginous illite-smectite (I-S) is the most common clay mineral, although kaolins dominate some samples. Antibacterial clay mineral assemblages may also contain non-clay reduced Fe-minerals (e.g., pyrite) that oxidize, causing damage to cell membranes and intracellular proteins. The key is that the clay mineral assemblage buffers the hydration water to pH and Eh conditions that release metals critical to the antibacterial process, allowing interaction with the bacteria. Antibacterial clays also exchange structural ions with the bacterial membrane that weaken bacterial defenses. This research will take this new understanding of the antibacterial process, to the next level by testing their effect on biofilms. Infectious diseases in humans commonly form biofilms, which are communities of bacteria more resistant to antibiotics than the "free floating" bacterial suspensions tested. The effectiveness of antibacterial clay on biofilms is an important step in supporting the costly testing of the bactericidal effect in animal trials. If antibacterial clay is effective against biofilms, in vivo testing may lead to design of new treatments for antibiotic resistant bacteria, with potential applications in wound dressings, medical implants (joint replacements, catheters), animal feed stocks, agricultural pathogens, and production of antibacterial building materials. The scientific goal of this research is to document the effect of an antibacterial clay previously tested against a broad spectrum of planktonic human pathogens, on biofilms most common to infectious diseases. In collaboration with infectious disease researchers at the Mayo Clinic (Rochester, MN), the investigator will develop protocols for the application of clays to biofilms and evaluate conditions that lead to, or limit, their antibacterial activity. Clinical isolates of common and antibiotic resistant bacterial strains will be tested. The investigator has demonstrated that antibacterial clays release metals (Aluminum, Iron) that act together to damage cell membranes and intracellular proteins so they will monitor the interaction of these metals with the biofilms. Standard methods for testing antibiotics must be modified for testing natural clay because the minerals, while releasing metals, are not completely dissolved and therefore will affect spectroscopic evaluations of bacterial viability. Furthermore, the investigator found that metal speciation in various growth media affect results by limiting metal reactivity with bacteria. Therefore, healthy biofilms grown on Teflon disks will be incubated with clay suspensions and cultures will be evaluated for viability by serial dilution and plate counting. If successful, this project will bridge the gap between mineralogy and medicine promoting applications of clay or its derivatives to antibiotic resistant infections. This will enhance development of medical protocols for evaluating minerals that improve human health. The ultimate benefit to society will be to establish an economical and safe natural mineral cure for antibiotic-resistant infections. Proof of the antibacterial activity and safety for applications in wound care may lead to an economic use of clays to treat wounds, or to development of new medicines that incorporate similar antibacterial properties.