Comparison of Inhibitory Effects of Nisin, Glycine, Poly-L-lysine, Magnesium Oxide Nanoparticles and Peganum harmala Extract on Standard and Multidrug-Resistant Pseudomonas aeruginosa

Background and Aims: Pseudomonas aeruginosa is one of the most important common causes of nosocomial infections that its standard and antibiotic-resistant strains can infect critical body organs such as the lungs and the urinary tract. In this study, inhibitory effects of nisin, glycine, poly-L-lysine, magnesium oxide nanoparticles and hydroalcoholic extract of Peganum harmala were assessed against standard and multidrug-resistant strains of P. aeruginosa. Materials and Methods: MgO nanoparticles with sizes of around 30-50 nm were synthesized via wet chemical method. Their structure were characterized using X-ray diffraction (XRD) analysis and scanning electron microscope (SEM). P. harmala seed extract was prepared by soaking in water-ethanol 1:1. Solutions of glycine, poly-L-lysine and nisin were prepared, and sterilized using 0.22 μm filter. Inhibitory effects of all compounds as inhibition zone diameter (IZD), the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) values were determined according to CLSI guidelines using disk diffusion and broth microdilution methods. Results and Conclusions: No significant inhibitory effects against P. aeruginosa were observed at the highest used concentrations of glycine, poly-L-lysine, MgO nanoparticles and plant extract. Inhibitory effects against both standard and resistant strains were only recorded for nisin with inhibition zone diameter of 10.36, 13.08 mm, MIC of 64, 128 μg/mL and MBC of 256, 512 μg/mL. Nisin as a natural food preservative can be used alone or in combination with current antibiotics to treat diseases caused by P. aeruginosa