Antibiofilm activity of silver nanoparticles against biofilm forming Staphylococcus pseudintermedius isolated from dogs with otitis externa

Background: Silver nanoparticles (AgNPs) are known to possess antimicrobial properties. Although the antibiofilm activity of AgNPs has been demonstrated in humans, this activity has not yet been elucidated in veterinary medicine. Objectives: The purpose of this study was to evaluate the antibiofilm activity of silver nanoparticles against Staphylococcus pseudintermedius. Methods: Ten isolates of S. pseudintermedius obtained from dogs with otitis externa were treated with AgNPs, and the antibiofilm activity was measured using a modified microtiter plate and Congo red agar (CRA) method and scanning electron microscopy. Results: AgNPs displayed a significant dose-dependent antibiofilm activity and reduced biofilm formation at concentrations of 20 and 10 µg/ml (p < 0.05). S. pseudintermedius exposed to 20 µg/ml of AgNPs formed less bacterial slime compared to the controls on CRA plates. Scanning electron micrographs showed that the biofilm had few individually scattered cells along its surface when treated with AgNP concentrations of 20 and 10 µg/ml. Untreated surfaces showed an aggregated biofilm. Conclusions: Our results suggested that AgNP may be a valuable alternative antibiofilm agent for canine otitis externa.