|INGUDAM, SHAKUTALA - INDIAN COUNCIL OF AGRICULTURAL RESEARCH (ICAR)|
Submitted to: Journal of Nanobiotechnology (Biomed Central Open Access)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2016
Publication Date: 6/27/2016
Publication URL: http://handle.nal.usda.gov/10113/5852144
Citation: He, Y., Ingudam, S., Reed, S.A., Gehring, A.G., Strobaugh Jr, T.P., Irwin, P.L. 2016. Study on the mechanism of antibacterial action of magnesium oxide nanoparticles against foodborne pathogens. Journal of Nanobiotechnology (Biomed Central Open Access). DOI:10.1186/s12951-016-0202-0.
Interpretive Summary: Methods to inactivate harmful bacteria in food are needed to prevent foodborne illness. The antibacterial activity of magnesium oxide (MgO) nanoparticles was investigated against three major foodborne pathogens (Campylobacter, Salmonella, and E. coli O157:H7). Our results showed the nanoparticles are effective both on inhibiting bacteria growth and completely killing cells. Investigation of the mechanism of nanoparticles against microbial pathogens showed that nanoparticles altered cell shape and membrane integrity. Moreover, these nanoparticles produced hydrogen peroxide and induced oxidative stress in bacteria to cause cell death. The understanding of the mechanism of the antibacterial effect of MgO nanoparticles on foodborne pathogens will provide us guidelines for the rational design and synthesis of effective antimicrobial agents that can be used during food processing.
Technical Abstract: Magnesium oxide nanoparticles (MgO nanoparticles, with average size of 20 nm) have strong antibacterial activities against several important foodborne pathogens. Resazurin (a redox sensitive dye) microplate assay was used for measuring growth inhibition of bacteria treated with MgO nanoparticles. The minimal inhibitory concentrations (MIC) of MgO nanoparticles to 104 CFU/ml of C. jejuni, E. coli O157:H7, and S. Enteritidis were determined to be 1, 2, and 0.5 mg/ml, respectively. To completely inactivate 10**8-9 CFU/ml bacterial cells in 4 hrs, a minimal concentration of 2 mg/ml MgO nanoparticles was required for C. jejuni whereas E. coli O157:H7 and S. Enteritidis required at least 8 mg/ml nanoparticles. Scanning electron microscopy examination revealed clear morphological changes and membrane structural damage in the cells treated with MgO nanoparticles. Ethidium monoazide (EMA)-qPCR analysis confirmed cell membrane permeability was increased after exposure to nanoparticles. In a cell free assay, a low level (1.1 micro M) of H2O2 was detected in the nanoparticle suspensions. Consistently, MgO nanoparticles greatly induced the expression of anti-oxidative stress genes in C. jejuni. All together, these results suggested that the interaction of nanoparticles with bacterial cells causes cell membrane leakage, induces oxidative stress, and ultimately leads to cell death.