Antibacterial clays in nature include a variety of clay mineral assemblages that are capable of killing certain human pathogens. Although clays have been used for medicinal applications historically, only in the last decade have analytical methods and instrumentation been developed that allow researchers to evaluate the antibacterial mechanisms of various clays applied medicinally. Comparisons of the mineralogical and chemical compositions of natural clays that kill bacteria have promoted a better understanding of the mineral properties that are toxic to a broad-spectrum of human pathogens, including bacteria that have developed resistance to antibiotics. Popular literature is filled with reports of ‘healing’ clays, that, when tested against pathogens in vitro and compared to controls, do not appear to have bactericidal properties. It is important, however, to differentiate what properties make a clay ‘healing,’ versus what makes a clay ‘antibacterial.’ Most antibacterial clays identified to date buffer pH conditions of a hydrated clay outside the range of conditions in which human pathogens thrive (circum-neutral pH) and require oxidation reactions to occur. It is the change in oxidation state and pH imposed by the hydrated clay, applied topically, that leads to a chemical attack of the bacteria. Healing clays, on the other hand, may not kill bacteria but have soothing effects that are palliative. This article reviews some of the historical uses of clays in medicine but focuses primarily on the common characteristics of natural antibacterial clays and early studies of their antibacterial mechanisms. In this era of bacterial resistance to antibiotics, mimicking the antibacterial mechanisms exhibited by natural clays could be advantageous in the development of new antimicrobial agents.

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天然抗菌粘土：历史用途和现代进步

自然界中的抗菌粘土包括各种能够杀死某些人类病原体的粘土矿物组合。虽然粘土在历史上已被用于医药应用，但直到最近十年才开发出分析方法和仪器，使研究人员能够评估各种医药应用粘土的抗菌机制。对杀死细菌的天然粘土的矿物学和化学成分的比较促进了对对广谱人类病原体（包括对抗生素产生抗药性的细菌）有毒的矿物特性的更好理解。流行的文献中充斥着“愈合”粘土的报告，当在体外针对病原体进行测试并与对照相比时，它们似乎没有杀菌特性。这很重要，然而，要区分什么特性使粘土“愈合”，而什么特性使粘土“抗菌”。迄今为止，大多数抗菌粘土确定了水合粘土的缓冲 pH 条件超出了人类病原体繁殖的条件范围（循环中性 pH）并需要发生氧化反应。水合粘土局部施加的氧化态和 pH 值的变化导致细菌的化学攻击。另一方面，愈合粘土可能不会杀死细菌，但具有缓解作用的舒缓作用。本文回顾了粘土在医学中的一些历史用途，但主要侧重于天然抗菌粘土的共同特征及其抗菌机制的早期研究。在这个细菌对抗生素耐药的时代，