[01] Lawrence Sheringham Borquaye, Department of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana; Central Laboratory, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana. [02] Edward Ocansey, Department of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana. [03] Julius Semenya, Department of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.

Clay and other mineral products have been documented as remedies for numerous human diseases throughout history with a number of success stories. In this study, the antimicrobial activity of the aqueous leachates of five clay samples collected from Keta, Anloga, Half-Assini, Sogakope and Savietula, all in Ghana, were examined. The in vitro antimicrobial activity of the aqueous leachates were tested against nine microbes using agar well diffusion assay. Of the five clay samples, Sogakope clay leachate possessed the highest antimicrobial activity, showing varying zones of inhibitions against all nine test microorganisms. All other leachates exhibited antimicrobial activity against at least one of the test microbes, except for clay leachate from Anloga which was inactive towards all microbes used in this study. pH and conductivity measurements indicated that Sogakope aqueous leachate had the lowest pH of 2.81 and a conductivity of 54.2 μS/cm while aqueous leachates of Anloga, Keta, Half-Assini and Savietula clays had pH values of 10.27, 7.66, 4.88, 8.01 and conductivities of 94.8, 5.86, 2.02, 91.40 μS/cm respectively. Metal analysis revealed that all clay samples have comparable compositions. Clay deposits may potentially provide cost-effective topical antibacterial treatments.

Agar Diffusion, Leachates, Metal Ions, Conductivity, pH

[01] S. Donadio, S. Maffioli, P. Monciardini, M. Sosio, and D. Jabes, “Antibiotic discovery in the twenty-first century: current trends and future perspectives,” J. Antibiot. (Tokyo)., vol. 63, no. 8, pp. 423–430, Jun. 2010. [02] M. A. Fischbach and C. T. Walsh, “Antibiotics for emerging pathogens.,” Science (80-.)., vol. 325, no. 5944, pp. 1089–93, Aug. 2009. [03] D. J. Newman, G. M. Cragg, and K. M. Snader, “Natural products as sources of new drugs over the period 1981-2002.,” J. Nat. Prod., vol. 66, no. 7, pp. 1022–37, Jul. 2003. [04] A. L. Harvey, “Natural products in drug discovery.,” Drug Discov. Today, vol. 13, no. 19–20, pp. 894–901, Oct. 2008. [05] A. Debbab and A. Aly, “Bioactive compounds from marine bacteria and fungi,” Microb. Biotechnol., vol. 3, no. 5, pp. 544–563, 2010. [06] M. Cueto and P. Jensen, “Pestalone, a new antibiotic produced by a marine fungus in response to bacterial challenge,” J. Nat. Prod., vol. 64, no. 11, pp. 1444–1446, 2001. [07] M. Gaynor and A. Mankin, “Macrolide Antibiotics: Binding Site, Mechanism of Action, Resistance,” Curr. Top. Med. Chem., vol. 3, no. 9, pp. 949–960, May 2003. [08] M. A. Kohanski, D. J. Dwyer, and J. J. Collins, “How antibiotics kill bacteria: from targets to networks.,” Nat. Rev. Microbiol., vol. 8, no. 6, pp. 423–35, Jun. 2010. [09] P. Silva, S. Oliveira, and L. Farias, “Chemical and radiological characterization of clay minerals used in pharmaceutics and cosmetics,” Appl. Clay Sci., vol. 52, no. 1–2, pp. 145–149, 2011. [10] G. Volpato, P. Kourková, and V. Zelený, “Healing war wounds and perfuming exile: the use of vegetal, animal, and mineral products for perfumes, cosmetics, and skin healing among Sahrawi,” J. Ethnobiol. Ethnomed., vol. 8, no. 49, pp. 1–19, 2012. [11] S. Haydel, “Broad-spectrum in vitro antibacterial activities of clay minerals against antibiotic-susceptible and antibiotic-resistant bacterial pathogens,” J. Antimicrob. Chemother., vol. 61, no. 2, pp. 353–361, 2008. [12] C. Viseras, C. Aguzzi, P. Cerezo, and A. Lopezgalindo, “Uses of clay minerals in semisolid health care and therapeutic products,” Appl. Clay Sci., vol. 36, no. 1–3, pp. 37–50, Apr. 2007. [13] M. Newman and E. Frimpong, “Resistance to antimicrobial drugs in Ghana,” Infect. Drug Resist., vol. 4, pp. 215–220, 2011. [14] C. C. Otto and S. E. Haydel, “Exchangeable Ions Are Responsible for the In Vitro Antibacterial Properties of Natural Clay Mixtures,” PLoS One, vol. 8, no. 5, p. e64068, May 2013. [15] C. C. Otto, J. L. Koehl, D. Solanky, and S. E. Haydel, “Metal Ions, Not Metal-Catalyzed Oxidative Stress, Cause Clay Leachate Antibacterial Activity,” PLoS One, vol. 9, no. 12, p. e115172, 2014. [16] L. Williams, S. Haydel, R. Giese Jr, and D. Eberl, “Chemical and mineralogical characteristics of French green clays used for healing,” Clays Clay Miner., vol. 58, no. 4, pp. 437–452, 2008. [17] A. McLaren, “Biochemistry and soil science,” Science (80-.)., vol. 141, no. 3586, pp. 1141–1147, 1963. [18] J. Moberly, A. Staven, R. Sani, and B. Peyton, “Influence of pH and inorganic phosphate on toxicity of zinc to Arthrobacter sp. isolated from heavy-metal-contaminated sediments,” Environ. Sci. Technol., vol. 44, no. 19, pp. 7302–7308, 2010. [19] N. Franklin, J. Stauber, S. Markich, and R. Lim, “pH-dependent toxicity of copper and uranium to a tropical freshwater alga (Chlorella sp.),” Aquat. Toxicol., vol. 48, no. 2–3, pp. 275–289, 2000. [20] T. Cunningham, J. Koehl, J. Summers, and S. Haydel, “pH-dependent metal ion toxicity influences the antibacterial activity of two natural mineral mixtures,” PLoS One, vol. 5, no. 3, p. e9456, 2010.