Photodynamic and antibiotic therapy in combination against bacterial infections: efficacy, determinants, mechanisms, and future perspectives

Antibiotic treatment, the mainstay for the control of bacterial infections, is greatly hampered by the global prevalence of multidrug-resistant (MDR) bacteria. Photodynamic therapy (PDT) is effective against MDR infections, but PDT-induced bacterial inactivation is often incomplete, causing the relapse of infections. Combination of PDT and antibiotics is a promising strategy to overcome the limitation of both antibiotic treatment and PDT, exerting increased disinfection efficacy on MDR bacterial pathogens versus either of the monotherapies alone. In this review, we present an overview of the therapeutic effects of PDT/antibiotic combinations that have been developed. We further summarize the influencing factors and the governing molecular mechanisms of the therapeutic outcomes of PDT/antibiotic combinations. In the end, we provide concluding remarks on the strengths, limitations, and future research directions of PDT/antibiotic combination therapy to guide its appropriate usage and further development.