Bio-reactive clay minerals and anthrax decontamination: a novel antimicrobial solution

Bacillus anthracis, the cause of Anthrax, is endemic to large swathes of Africa and South America. Its endospores persist in the environment and are the primary cause of infection (to animals and humans). Multiple state actors and terrorism groups have utilised the spores as bioweapons. Current methods of decontamination, whilst effective, cause environmental decimation and are themselves environmentally toxic. Thus, it is desirable to consider novel methods for decontamination of affected environments. Recently, some bio-reactive clays have demonstrated antimicrobial properties. Geochemical investigation by X-ray diffraction and Inductively-coupled plasma mass spectroscopy on a range of test clay minerals has been undertaken to help elucidate the mechanism of action. Antimicrobial ability was assessed using viability counts of hydrated clay minerals on both vegetative cells and spores of Sterne strain B. anthracis. One clay (‘French Green’) has shown Log105 reduction of viable colonies in both vegetative cells and spores (0.15g/ml and 0.05g/ml, respectively) after 20-hour incubation. French Green clay is 91% quartz mineral and has been used as a topical treatment for cutaneous Mycobacterium Ulcerans infections. These results support previous studies on other organisms. Further in-vitro toxicological studies will be employed to determine the activity of antimicrobial clay minerals on human tissue models; to ensure that deployment of the clay as an environmental decontaminant would not be hazardous to inhabitants. This study will aid the understanding of the action mechanism of antimicrobial clays and help determine the possibility of clay mineral usage as an environmental decontamination solution for bacterial contaminants