Inhibitory Effects of Honokiol and Magnolol on Biofilm Formation by Acinetobacter baumannii

Acinetobacter baumannii is a nosocomial pathogen that can survive unfavorable conditions, such as, desiccation, nutrient starvation, and antimicrobial treatment, and this is primarily due to its ability to form biofilms on biotic and abiotic surfaces like tissues and medical devices. In this study, honokiol and magnolol were investigated for antibiofilm activity against A. baumannii ATCC 17978. Both were found to inhibit biofilm formation dose-dependently and to disperse matured biofilms. Honokiol and magnolol were found to inhibit biofilm formation by five and four of eight additional clinical A. baumannii isolates, respectively. Furthermore, honokiol and magnolol effectively suppressed pellicle formation and the surface motilities of the A. baumannii and prolonged the survival of infected nematode Caenorhabditis elegans. These results demonstrate that honokiol and magnolol may be useful for controlling A. baumannii infections.