In their studies with gramnegative, E. coli, and gram-positive, S. aureus, Kim et al. reported greater biocidal efficiency of silver nanoparticles for E. coli, and attributed it to difference in cell wall structure between gram
negative and gram positive microorganisms. However, currently there is insufficient evidence to support such conclusions since most research on bactericidal effect of nanoparticles has been conducted with one or a very limited number of microbial strains