MARIOARA NICOLETA FILIMON, ROXANA POPESCU3, ADRIAN SINITEAN, PAULA MANIU, GABI DUMITRESCU, DOINA VERDES, CRISTIAN SEBASTIAN VLAD THE ASSESSMENT OF CHITOSAN SOLUTIONS EFFECTS ON BACTERIAL STRAINS The interest in the antimicrobial actions of chitosan is due to its multiple properties and effects. The aim of the study was to assess the potential antibacterial effects of chitosan applied on 7 bacterial strains: Escherichia coli, Streptococcus pyogenes, Pseudomonas aeruginosa, Enterococcus faecalis, Clostridium perfringens, Legionella pneumophila and Staphylococcus aureus. Six different concentrations of chitosan were dissolved in 1% acetic acid, following two working protocols (Kirby-Bauer method and testing for bacterial cell viability). The sensitivity of tested bacterial strains following the effect of exposure to chitosan decreased as follows: E. coli> L. pneumophila> S. aureus> S. pyogenes> C. perfringens> P. aeruginosa> E. faecalis. The inhibition rates for the bacterial strains E. faecalis, S. pyogenes and S. aureus highlighted again the strong antibacterial properties of this product. Conclude that the chitosan presents a different antibacterial effect against several bacterial strains of interest directly with the employed concentrations.