Chitosan nanoparticles enhance the antibacterial activity of the native polymer against bovine mastitis pathogens

•Chitosan nanoparticles showed better antimicrobial activity than native chitosan.•Chitosan nanoparticles inhibit biofilm formation of mastitis pathogens.•The antibiofilm efficiency of nanosized Chitosan was dose-dependent.•Chitosan nanoparticles do not damage the cells of the host organism.•Chitosan nanoparticles represent an effective antimicrobial treatment for mastitis. Staphylococcus is the most commonly isolated genus from animals with intramammary infections, and mastitis is the most prevalent disease that affects dairy cows in many countries. These pathogens can live in biofilms, a self-produced matrix, which allow them evade the innate immune system and the antibiotic therapy, thereby producing persistent infections. The aim of this study was to explore the antimicrobial potential of chitosan nanoparticles (Ch-NPs) obtained by the reverse micellar method. We found that the nanoformulation developed presents antimicrobial activity against mastitis pathogens in a dose-dependent manner. Moreover, different experiments corroborated that the antimicrobial effectiveness of Ch-NP was greater than that shown by the native polymer used in the preparation of these nanocomposites. Ch-NPs caused membrane damage to bacterial cells and inhibited bacterial biofilm formation, without affecting the viability of bovine cells. These findings show the great potential of Ch-NPs as therapeutic agent for bovine mastitis treatment.