Shanghai Medical College of Fudan University 1 article published in JoVE Biology An In Vitro Model to Study the Effect of 5-Aminolevulinic Acid-mediated Photodynamic Therapy on Staphylococcus aureus Biofilm Ke-Qing Zhao*1, Yang Wu*2, Yu-Xi Yi2, Si-Jia Feng2, Ruo-Yan Wei2, Ying Ma3, Chun-Quan Zheng1, Di Qu2 1Department of Otorhinolaryngology-Head and Neck Surgery, Eye & ENT Hospital, Shanghai Key Clinical Disciplines of otorhinolaryngology, Fudan University, 2Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Department of Medical Microbiology and Parasitology, School of Basic Medical Science, Shanghai Medical College of Fudan University, 3Department of Dermatology, Huashan Hospital, Fudan University This manuscript describes a protocol to study the antimicrobial effect of 5-aminolevulinic acid-mediated photodynamic therapy (ALA-PDT) on a Staphylococcus aureus biofilm. This protocol can be used to develop an in vitro model to study the treatment of bacterial biofilms with PDT in the future.