BACTERICIDAL PROPERTIES OF CLAYS USED FOR TREATMENT OF BURULI ULCER- AN EMERGING PUBLIC HEALTH THREAT

The World Health Organization (WHO) recently declared Buruli ulcer an emerging public health threat and called for increased surveillance, control, and research efforts to diagnose, treat, and prevent this disease. Increasingly common, particularly among children, this disfiguring illness is caused by Mycobacterium ulcerans. High incidents of this disease are reported in much of central and western Africa. Currently, there is no WHO-accepted therapeutic treatment available for Buruli ulcer. The only medically-accepted treatment of M. ulcerans infection is removing diseased tissue, skin grafting and (or) amputation. Because the disease often occurs within poor rural communities; surgical procedures are unlikely treatment options. However, these populations have addressed the limitations through the therapeutic use of clays. One therapy involved moistened French clay, known as Agricur, to heal Buruli disease. To date over 50 cases have been documented of curing Buruli ulcer with clay therapy.

This study involved assessing different clays for broad spectrum bactericidal/bacteriostatic effects, identifying specific, toxic components of the clay mineral responsible for antibacterial activity, and monitoring chemical exchange between the mineral and bacteria.

We used several different clays, including sterile sand and the French clay used in the documented healing cases, to assess their broad-spectrum bactericidal effects. Several different bacterial species and type (Salmonella typhimurium, Streptococcus sp. Escherichia coli, Pseudomonas stutzeri) also were used in our assessments. The experimental matrix was tested both by incubation of bacterial cultures in the presence of clay and by incubation with the clay separated from the bacteria by dialysis tubing (25k MWCO). We found that bacterial cultures lost 90-99% of viability within 24 hours of exposure to the French Agricur clays, as did bacterial cultures suspended in dialysis tubing. These results contrasted to only 10-40% of reduced viability caused by other clays or sterile sand. These initial experiments suggest bactericidal effects for these clays, but the mechanisms of action remain unknown and deserve further study.