Bactericidal effects of toluidine blue-mediated photodynamic action on Vibrio vulnificus
Tak-Wah Wong1, Yin-Yi Wang, Hamm-Ming Sheu
1Department of Dermatology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Abstract:
Vibrio vulnificus is a gram-negative, highly invasive bacterium responsible for human opportunistic infections. We studied the antibacterial effects of toluidine blue O (TBO)-mediated photodynamic therapy (PDT) for V. vulnificus wound infections in mice. Fifty-three percent (10 of 19) of mice treated with 100 microg of TBO per ml and exposed to broad-spectrum red light (150 J/cm(2) at 80 mW/cm(2)) survived, even though systemic septicemia had been established with a bacterial inoculum 100 times the 50% lethal dose. In vitro, the bacteria were killed after exposure to a lower light dose (100 J/cm(2) at 80 mW/cm(2)) in the presence of low-dose TBO (0.1 microg/ml). PDT severely damaged the cell wall and reduced cell motility and virulence. Cell-killing effects were dependent on the TBO concentration and light doses and were mediated partly through the reactive oxygen species generated during the photodynamic reaction. Our study has demonstrated that PDT can cure mice with otherwise fatal V. vulnificus wound infections. These promising results suggest the potential of this regimen as a possible alternative to antibiotics in future clinical applications.
Insights
Photodynamic therapy (PDT) using toluidine blue O (TBO) effectively treated fatal Vibrio vulnificus wound infections in mice. This novel approach offers a promising alternative to traditional antibiotics for bacterial infections.
Area of Science:
- Microbiology
- Biomedical Engineering
- Photomedicine
Background:
- Vibrio vulnificus is a dangerous gram-negative bacterium causing severe opportunistic infections.
- Antibiotic resistance necessitates alternative treatment strategies for bacterial infections.
Purpose of the Study:
- To evaluate the efficacy of toluidine blue O (TBO)-mediated photodynamic therapy (PDT) against Vibrio vulnificus wound infections in a murine model.
- To investigate the mechanisms underlying PDT's antibacterial effects on V. vulnificus.
Main Methods:
- In vivo study using a mouse model of V. vulnificus wound infection.
- In vitro assessment of TBO-PDT's bactericidal activity.
- Analysis of bacterial cell wall integrity, motility, and virulence factors post-treatment.
- Measurement of reactive oxygen species (ROS) generation.
Main Results:
- PDT with TBO and red light significantly improved survival rates in mice with established V. vulnificus septicemia.
- In vitro, low-dose TBO-PDT eradicated V. vulnificus with reduced light exposure.
- PDT induced severe damage to the bacterial cell wall, reduced motility, and decreased virulence.
- Antibacterial effects were dose-dependent on TBO concentration and light exposure, mediated by ROS.
Conclusions:
- TBO-mediated PDT demonstrates potent antibacterial activity against V. vulnificus, even in severe infections.
- PDT offers a promising alternative to antibiotics for treating V. vulnificus infections.
- Further research into PDT as a clinical application for bacterial wound infections is warranted.
