Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/26/2015
Publication Date: 5/30/2015
Citation: Reed, S.A., Ingudum, S., Irwin, P.L., He, Y. 2015. Antimicrobial properties and mechanism of magnesium oxide nanoparticles on Campylobacter, E. coli O157:H7, and Salmonella. Meeting Abstract. meeting abstract. Interpretive Summary:
Technical Abstract: Background: Metal oxide nanoparticles have considerable potential as antimicrobial agents in food safety applications due to their structure, surface properties, and stability. In this study, the antibacterial effects and mechanisms of Magnesium Oxide Nanoparticles (MgO NPs, with an average size of 20 nm), against several important food-borne pathogens were investigated. Materials: The viability of Campylobacter jejuni, E. coli O157:H7, and Salmonella Enteritidis when exposed to varying concentrations of MgO NPs was measured using Resazurin, a redox sensitive dye. The time course required for complete killing of cells at 109 CFU/ml was determined by 6x6 drop plating. Ethidium monoazide-quantitative PCR (EMA-qPCR) and scanning electron microscopy (SEM) were used to evaluate membrane permissibility and cell morphology after exposure to MgO NPs. The molecular basis of the action of MgO NPs on bacterial cells was studied by monitoring the expression of genes involved in stress response using reverse transcription-qPCR. Quantification of hydrogen peroxide generated by MgO NP suspensions was carried out using the red hydrogen peroxide assay kit. Results: The minimal inhibitory concentrations (MIC) of MgO NPs were 0.5, 1, and 2 mg/mL for 104 CFU/ml of C. jejuni, E. coli O157:H7, and S. Enteriditis, respectively, after 18 hours incubation. At a concentration of 2 mg/ml MgO NPs, C. jejuni cells were completely killed within 2 hours, whereas E. coli O157:H7 and S. Enteriditis required 6-8 hours with 2-4 mg/ml MgO NPs. After exposure to the nanoparticles, all of the cells displayed notable morphological changes and membrane leakage by SEM and EMA-qPCR analyses, respectively. Furthermore, MgO NPs produced H2O2 in suspension and significantly induced the expression of oxidative stress genes in C. jejuni, suggesting that the antimicrobial mechanism of MgO nanoparticles is likely due to the induction of oxidative stress. Conclusion: The demonstrated antimicrobial activity of MgO NPs on major food-borne pathogens suggest that they could potentially be used as food additives or incorporated into packaging materials to control the pathogens. The understanding of the molecular basis of MgO NP action on bacteria will lead to the development of more effective antimicrobial agents for food safety applications.