Abstract
Natural clays have recently been proven to possess antibacterial properties. Effective natural antimicrobial agents are needed to combat bacterial contamination on food contact surfaces, which are increasingly more prevalent in the food chain. This study sought to determine the antibacterial activity of clays against the food-borne pathogens Salmonella typhimurium ATCC 14028 and Staphylococcus aureus ATCC 13565. Soils were processed to yield leachates and suspensions from untreated and treated clays. Soil particle size, pH, cation-exchange capacity, metal composition and mineralogy were characterized. Antibacterial screening was performed on six Malaysian soils via the disc diffusion method. In addition, a time-kill assay was conducted on selected antibacterial clays after 6 h of exposure. The screening revealed that Munchong and Carey clays significantly inhibit Salmonella typhimurium (11.00 ± 0.71 mm) and S. aureus (7.63 ± 0.48 mm), respectively. Treated Carey clay leachate and suspension completely kill Salmonella typhimurium, while S. aureus viability is reduced (2 to 3 log10). The untreated Carey and all Munchong clays proved ineffective as antibacterials. XRD analysis confirmed the presence of pyrite and magnetite. Treated Carey clays had a higher soluble metal content compared to Munchong; namely Al (92.63 ± 2.18 mg/L), Fe (65.69 ± 3.09 mg/L) and Mg (88.48 ± 2.29 mg/L). Our results suggest that metal ion toxicity is responsible for the antibacterial activity of these clays.
Highlights
Halal Products Research Institute, Universiti Putra Malaysia, Serdang 43400, Malaysia; Faculty of Food Science and Technology, Universiti Putra Malaysia, Serdang 43400, Malaysia; Abstract: Natural clays have recently been proven to possess antibacterial properties
Studies have found a high degree of cross-contamination of various pathogens including Salmonella typhimurium, a Gram-negative enterobacterial pathogen and Staphylococcus aureus, a Gram-positive species associated with skin infections due to inadequate cleaning and disinfection of cutting boards [3,4]
In view of emerging science describing clay as an efficient killing agent against several bacterial pathogens, this study investigates the antibacterial activity of clay from Selangor, Malaysia against food-borne bacterial pathogens in an effort to demonstrate the potential of naturally produced clay as alternative sanitizing agents for the food industry
Summary
Halal Products Research Institute, Universiti Putra Malaysia, Serdang 43400, Malaysia; Faculty of Food Science and Technology, Universiti Putra Malaysia, Serdang 43400, Malaysia; Abstract: Natural clays have recently been proven to possess antibacterial properties. Aside from its healing and soothing properties, clay has been investigated for its antibacterial activities, exemplified by the successful application of French green clay in the treatment of Buruli ulcer, a necrotizing cutaneous infection caused by Mycobacterium ulcerans [1] and the antibacterial efficacy of clay leachates against Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) [2]. These studies have stimulated interest in the identification of clays from other localities that possess antibacterial activity and could be utilized as new antibacterial agents. In view of emerging science describing clay as an efficient killing agent against several bacterial pathogens, this study investigates the antibacterial activity of clay from Selangor, Malaysia against food-borne bacterial pathogens in an effort to demonstrate the potential of naturally produced clay as alternative sanitizing agents for the food industry
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