EAGER: Antibacterial clay effects on pathogenic biofilms

研究人员最近对粘土的研究表明，粘土可以杀死人类病原体，包括耐甲氧西林S。金黄色葡萄球菌（MRSA），记录了它们的共同特征。在全球范围内，迄今为止研究的粘土中只有5- 10%在水合和体外测试时具有抗菌性。大多数抗菌粘土来自热液蚀变火山岩，其中火山流体产生含有还原金属的矿物。含铁伊利石-蒙皂石（I-S）是最常见的粘土矿物，尽管高岭土在某些样品中占主导地位。抗菌粘土矿物组合物还可以含有非粘土还原的Fe-矿物（例如，黄铁矿）氧化，导致细胞膜和细胞内蛋白质的损伤。关键是粘土矿物组合物将水合水缓冲到pH和Eh条件，释放对抗菌过程至关重要的金属，从而允许与细菌相互作用。抗菌粘土还与细菌膜交换结构离子，削弱细菌防御。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。人类的传染病通常形成生物膜，生物膜是比测试的“自由漂浮”细菌悬浮液更耐抗生素的细菌群落。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膜有效，体内测试可能会导致设计新的抗生素耐药细菌治疗方法，在伤口敷料，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中具有潜在的应用。这项研究的科学目标是记录以前测试过的抗菌粘土对广泛的人类病原体的影响，对传染病最常见的生物膜的影响。与马约诊所（罗切斯特，明尼苏达州）的传染病研究人员合作，研究人员将制定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。将检测常见和抗生素耐药菌株的临床分离株。研究人员已经证明，抗菌粘土释放金属（铝，铁），这些金属一起作用，破坏细胞膜和细胞内蛋白质，因此他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测试天然粘土，因为矿物质，而释放金属，不完全溶解，因此会影响细菌活力的光谱评估。此外，研究人员发现，各种生长培养基中的金属形态通过限制金属与细菌的反应性来影响结果。因此，将在Teflon盘上生长的健康生物膜与粘土悬浮液一起孵育，并通过连续稀释和平板计数评价培养物的活力。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协议的发展。对社会的最终利益将是建立一种经济和安全的天然矿物治疗耐药性感染。伤口护理应用的抗菌活性和安全性的证明可能会导致粘土治疗伤口的经济用途，或开发具有类似抗菌性能的新药。

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.