Molecular weight and pH aspects of the efficacy of oligochitosan against methicillin-resistant Staphylococcus aureus (MRSA)

► Oligochitosan samples varying in molecular weight (0.73-20.0 kDa) were prepared. ► Oligochitosans form supramolecular aggregates in dilute solutions below the critical pH value 6.5. ► Bactericidal activity towards MRSA was determined at pH values 5.5-8.0. ► The aggregation does not prevent oligochitosan from demonstrating the antibacterial activity. ► The samples having Mw 3-5 kDa show high activity even at basic pH values.