BROAD-SPECTRUM IN VITRO ANTIBACTERIAL ACTIVITIES OF CLAY MINERALS AGAINST ANTIBIOTIC-SUSCEPTIBLE AND ANTIBIOTIC-RESISTANT BACTERIAL PATHOGENS

The capacity to properly address the worldwide incidence of infectious diseases lies in the ability to detect, prevent, and effectively treat these infections. Therefore, identifying and analyzing inhibitory agents are worthwhile endeavors in an era when few new classes of effective antimicrobials have been developed. Geological minerals have been used to heal skin infections since the earliest recorded history, and specific clay minerals may prove valuable in the treatment of bacterial diseases, including infections for which there are no effective antibiotics, such as Buruli ulcer and multi-drug resistant infections. We have subjected two iron-rich clay minerals, which have previously been used to treat Buruli ulcer patients, to broth culture susceptibility testing of susceptible and resistant pathogenic bacteria to assess the feasibility of using clay minerals as therapeutic agents. One specific mineral, CsAg02, demonstrated bactericidal activity against pathogenic Escherichia coli, extended-spectrum beta-lactamase (ESBL) E. coli, S. enterica serovar Typhimurium, Pseudomonas aeruginosa, and Mycobacterium marinum and a combined bacteriostatic/bactericidal effect against Staphylococcus aureus, penicillin-resistant S. aureus (PRSA), methicillin-resistant S. aureus (MRSA), and Mycobacterium smegmatis, while another mineral with similar structure and bulk crystal chemistry, CsAr02, had no effect on or enhanced bacterial growth. Our results indicate that specific mineral products have intrinsic antibacterial activities, which could provide an inexpensive treatment against numerous human bacterial infections.