Antimicrobial effects of magnesium oxide nanoparticles and ε-poly-L-lysine against Escherichia coli O157:H7 and Listeria monocytogenes

Microbial food contamination is of great threat to human health. Nanotechnology is considered as a promising solution to produce and develop such novel antimicrobial substances. The potential effects of nanostructured metal oxides on the reduction of such contaminants are well established. The present study was aimed to investigate the antimicrobial activities of magnesium oxide (MgO) nanoparticles and ε-poly-L-lysine against two major food borne bacteria, Escherichia coli O157:H7 and Listeria monocytogenes.
The minimum inhibitory concentration (MIC) values of the antimicrobial compounds, as single and in combination uses, against E. coli O157:H7 and L. monocytogenes were determined by resazurin reduction and micro-dilution methods, in order to calculate the fractional inhibitory concentration (FIC) index.
The growing of both microorganisms was inhibited by nano MgO at the concentration of 4.10 mg/ml and at the concentrations of 2.05 and 0.13 mg/ml, ε-poly-L-lysine was effective against E. coli and L. monocytogenes, respectively. The FIC indices of 0.52 and 0.75 against E. coli and L. monocytogenes, were respectively confirmed, when the combination of both antimicrobial agents was employed.
The current study was revealed the inhibitory effects of both substances against E. coli and L. monocytogenes. Furthermore, a limited synergy (0.5-0.75) was noticed in using them, in combination.