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Efficiency of Antimicrobial Photodynamic Therapy with Photodithazine® on MSSA and MRSA Strains
Beatriz Müller Nunes Souza1, Juliana Guerra Pinto1, André Henrique Correia Pereira1
1Laboratory of Photobiology Applied to Health, Research and Development Institute, University of Vale do Paraíba, Urbanova 2911, Brazil.
Abstract:
Staphylococccus aureus is a ubiquitous and opportunistic bacteria associated with high mortality rates. Antimicrobial photodynamic therapy (aPDT) is based on the application of a light source and a photosensitizer that can interact with molecular oxygen, forming Reactive Oxygen Species (ROS) that result in bacterial inactivation. This study aimed to analyze, in vitro, the action of aPDT with Photodithazine® (PDZ) in methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) strains. The strains were incubated with PDZ at 25, 50, 75, and 100 mg/L for 15 min and irradiated with fluences of 25, 50, and 100 J/cm2. The internalization of PDZ was evaluated by confocal microscopy, the bacterial growth by counting the number of colony-forming units, as well as the bacterial metabolic activity post-aPDT and the production of ROS. In both strains, the photosensitizer was internalized; the production of ROS increased when the aPDT was applied; there was a bacterial reduction compared to the control at all the evaluated fluences and concentrations; and, in most parameters, it was obtained complete inactivation with significant difference (p < 0.05). The implementation of aPDT with PDZ in clinical strains of S. aureus has resulted in its complete inactivation, including the MRSA strains.
Insights
Antimicrobial photodynamic therapy (aPDT) with Photodithazine effectively inactivates both methicillin-sensitive and resistant *Staphylococcus aureus* strains. This innovative approach shows significant bacterial reduction and complete inactivation, offering a promising alternative for treating *S. aureus* infections.
Area of Science:
- Microbiology
- Photomedicine
- Antimicrobial Therapy
Background:
- *Staphylococcus aureus* is a common pathogen causing severe infections.
- Antimicrobial photodynamic therapy (aPDT) uses photosensitizers and light to generate reactive oxygen species (ROS) for bacterial inactivation.
- Photodithazine (PDZ) is a photosensitizer investigated for its antimicrobial properties.
Purpose of the Study:
- To evaluate the in vitro efficacy of aPDT using Photodithazine against methicillin-sensitive *Staphylococcus aureus* (MSSA) and methicillin-resistant *Staphylococcus aureus* (MRSA).
- To assess PDZ internalization, ROS production, bacterial growth, and metabolic activity post-aPDT.
Main Methods:
- MSSA and MRSA strains were incubated with varying concentrations of PDZ (25-100 mg/L) for 15 minutes.
- Bacterial cultures were irradiated with different light fluences (25-100 J/cm²).
- PDZ internalization, ROS generation, colony-forming units (CFUs), and metabolic activity were measured.
Main Results:
- PDZ was successfully internalized by both MSSA and MRSA strains.
- aPDT application significantly increased ROS production.
- A notable reduction in bacterial counts was observed across all tested PDZ concentrations and light fluences.
- Complete bacterial inactivation was achieved in most experimental conditions, with statistically significant differences (p < 0.05).
Conclusions:
- aPDT with Photodithazine demonstrates potent antimicrobial activity against *Staphylococcus aureus*, including MRSA strains.
- This therapy offers a viable strategy for the complete inactivation of *S. aureus* in vitro.
- The findings support the potential clinical application of aPDT with PDZ for treating *S. aureus* infections.
