Photodynamic therapy of microbial infections: state of the art and perspectives

Area of Science:

• Biomedical Sciences
• Photochemistry
• Antimicrobial Therapies

Background:

• Antibiotic resistance is a growing global health crisis, necessitating novel therapeutic strategies.
• Photodynamic therapy (PDT) is emerging as a promising alternative to conventional antimicrobial treatments.
• Specific photosensitizers, like porphyrins and phthalocyanines, show broad-spectrum antimicrobial activity.

Purpose of the Study:

• To evaluate the efficacy of photodynamic therapy (PDT) as an alternative treatment for microbial infections.
• To highlight the advantages of using red light-absorbing photosensitizers in antimicrobial PDT.
• To demonstrate the potential of PDT against antibiotic-resistant microbial strains.

Main Methods:

• Utilizing phenothiazines, porphyrins, and phthalocyanines as photodynamic antimicrobial agents.
• Employing mild irradiation conditions and a single phototherapeutic protocol for broad-spectrum inactivation.
• Investigating the mechanism of microbial cell death via membrane photodamage.
• Demonstrating phthalocyanine-sensitized photoinactivation of methicillin-resistant Staphylococcus aureus (MRSA).

Main Results:

• Selected photosensitizers exhibit broad-spectrum antimicrobial action against Gram-positive and Gram-negative bacteria, fungi, mycoplasma, and parasites.
• Photosensitizers show no significant dark toxicity at photochemically active doses.
• The multitarget photodamage mechanism minimizes mutagenic processes and the selection of photoresistant cells.
• PDT demonstrates equal efficacy against wild-type and antibiotic-resistant strains, with no observed photoresistance selection.

Conclusions:

• Antimicrobial PDT is a viable and efficient alternative for combating microbial infections, especially those caused by resistant strains.
• The low risk of resistance development and broad applicability make PDT a valuable therapeutic option.
• PDT is particularly suitable for treating localized infections like oral candidosis, periodontitis, and chronic wounds.