Reducing the size of particles results in different physical and chemical properties, especially if the size is reduced below 1 μm. Reducing the size of particles below 1 μm opens up the possibility of finding new biologically active compounds. One of such biologically active compunds are nanoparticles of metals and metalic oxides (MNP), and therefore it is the cause of this paper to explore antimicrobial properties of MNP in colloid form. Colloid MNP show minimal bactericidal (MBC) and inhibitory (MIC) concentrations in ranges of 0,01 to 100 ppm. Lowest MIC and MBC values belong to colloid NP of ZnO, while highest values belong to colloid TiO2, however, colloid nanoparticles of ZrO2 demonstrate bacteriostatic effect in the entire range of tested concentrations, while bactericidal effect is absent. It has also been shown that antimicrobial efficacy of colloid Ag can be reduced by complex mediums, such as serum and protein solutions. Although MNP act through unspecific pathways, such as generations of reactive oxygen species (ROS) and penetration of cell membrane and wall, there are significant differences between methicillin-resistent (MRSA) and methicillin-sensitive (MSSA) strains of Staphyloccocus aureus. Synergism of nanoparticles was tested through fractionary bactericidal (FBCI) and inhibitory (FICI) concentration index, and combinations of colloid Ag, ZnO, and TiO2 show synergystic effect on MRSA, and antagonistic effect on MSSA. In the effort to test practical usage of MNP, a fabric of 1cm2 was impregnated with a layer of mixture of colloid MNP, and had its antimicrobial efficacy in time tested using „time-kill“ assay. Complete reduction of viable bacteria of strains MSSA and MRSA was achieved after 18 hours, with the fact that reduction of MRSA strain was faster than MSSA strain.