Effect of natural antibacterial clays against single biofilm formation by Staphylococcus aureus and Salmonella Typhimurium bacteria on a stainless-steel surface

• Published in: International journal of food microbiology 2023-06, Vol.394, p.110184-110184, Article 110184
• Main Authors: Wan Omar, Wan Hasyera, Mahyudin, Nor Ainy, Azmi, Nur Naqiyah, Mahmud Ab Rashid, Nor-Khaizura, Ismail, Roslan, Mohd Yusoff, Mohd Hafis Yuswan, Khairil Mokhtar, Nur Fadhilah, Sharples, Gary J.
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; Anti-biofilm; Antibacterial activity; Bacteria; biofilm; Biofilms; cation exchange capacity; Clay; Clay leachate; Clay suspension; disk diffusion antimicrobial test; food chain; food industry; food microbiology; leachates; particle size; public health; risk; Salmonella Typhimurium; species; Stainless Steel; Stainless-steel surface; Staphylococcus aureus
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/j.ijfoodmicro.2023.110184

Staphylococcus aureus and Salmonella Typhimurium have a propensity to develop biofilms on food contact surfaces, such as stainless-steel, that persist despite rigorous cleaning and sanitizing procedures. Since both bacterial species pose a significant public health risk within the food chain, improved anti-biofilm measures are needed. This study examined the potential of clays as antibacterial and anti-biofilm agents against these two pathogens on appropriate contact surfaces. Natural soil was processed to yield leachates and suspensions of both untreated and treated clays. Soil particle size, pH, cation-exchange capacity, and metal ions were characterized to assess their importance in bacterial killing. Initial antibacterial screening was performed on nine distinct types of natural Malaysian soil using a disk diffusion assay. Untreated leachate from Kuala Gula and Kuala Kangsar clays were found to inhibit S. aureus (7.75 ± 0.25 mm) and Salmonella Typhimurium (11.85 ± 1.63 mm), respectively. The treated Kuala Gula suspension (50.0 and 25.0 %) reduced S. aureus biofilms by 4.4 and 4.2 log at 24 and 6 h, respectively, while treated Kuala Kangsar suspension (12.5 %) by a 4.16 log reduction at 6 h. Although less effective, the treated Kuala Gula leachate (50.0 %) was effective in removing Salmonella Typhimurium biofilm with a decrease of >3 log in 24 h. In contrast to Kuala Kangsar clays, the treated Kuala Gula clays contained a much higher soluble metal content, especially Al (301.05 ± 0.45 ppm), Fe (691.83 ± 4.80 ppm) and Mg (88.44 ± 0.47 ppm). Elimination of S. aureus biofilms correlated with the presence of Fe, Cu, Pb, Ni, Mn and Zn irrespective of the pH of the leachate. Our findings demonstrate that a treated suspension is the most effective for eradication of S. aureus biofilms with a potential as a sanitizer-tolerant, natural antibacterial against biofilms for applications in the food industry. •Staphylococcus aureus and Salmonella Typhimurium form biofilms on food contact surfaces despite through cleaning and sanitizing procedures.•Clay from natural soils as a potential of antibacterial and anti-biofilm agents against these pathogens on contact surfaces.•Clay suspensions were more effective than leachates at bacterial eradication from the biofilms.•Elimination of S. aureus biofilms correlated with the presence of metal ions irrespective of the pH of the leachate.•Eradication of biofilms is clearly influenced by a variety of factors such as elemental c