Global increase of antibiotic-resistant pathogens as well as elevated content of drug residues in the foodstuffs and the environment urgently calls for new biocompatible antimicrobial biomaterials (1). Yeast mannans represent readily available source of biodegradable materials for tailor-made derivatives that could be effective in biomedical applications. Here, antimicrobial properties of quaternized mannans from Candida albicans against clinical multi-resistant strains of Staphylococcus aureus are confronted with possible cytotoxicity against human cells. As expected, both effects increase with increasing degree of quaternization. However, it is possible to define the “window”, at quaternized mannan with DS_Q 0.34 with good anti-microbial effectiveness and low cytotoxicity. This derivative exhibit minimum inhibitory and minimum bactericidal concentration from 62.5 to 250 µg/mL and demonstrate good biofilm inhibition effect. Also acceptable values were obtained in hemagglutination and hemolytic activity assays and also in cytotoxicity tests on human fibroblasts.