Intracellular Antimicrobial Photodynamic Therapy: A Novel Technique for Efficient Eradication of Pathogenic Bacteria

Abstract

The increasing resistance of bacteria to antibiotics is a serious problem, caused in part by excessive and improper use of these drugs. One alternative to traditional antibiotic therapy is photodynamic antimicrobial chemotherapy (PACT) which is based on the use of a photosensitizer (PS), activated by illumination with visible light. The poor penetration of visible light through the skin limits the application of PACT to the treatment of skin infections or the use of invasive procedures. To overcome this problem we report the exploitation of light emitted as a result of the chemiluminescent reaction of luminol to excite the PS and we call this process chemiluminescent photodynamic antimicrobial therapy (CPAT). We studied the effect of free and liposome-encapsulated PS (methylene blue or toluidine blue) on bacteria under excitation by either white external light or chemiluminescence emitted by free or liposome-enclosed luminol. PACT showed slightly better performance that CPAT for free and encapsulated PS for both types of bacteria. CPAT resulted in a three log suppression of Staphylococcus aureus and two log suppression of Escherichia coli growth. The use of CPAT may prove to be a novel and more effective form of antimicrobial therapy, particularly for internal infections not easily accessible to traditional PACT.

Olive Oil-Based Delivery of Photosensitizers for Bacterial Eradication

“…These results were explained by differences in photosensitizer chemistry which may influence their association with liposomal components, lipid fluidity and localization in liposome vesicles (Ferro et al, 2006;2007). We have previously shown that Methylene Blue encapsulated in liposomes composed of DPPC or EPC effectively deactivated several Gram-positive and Gram-negative bacteria, including S. lutea, E. coli, S. flexneri, S. aureus and MRSA, and that liposomal Rose Bengal also eradicated P. aeruginosa Nakonechny et al, 2010;.…”

Study of Methylene Blue Ototoxicity in the Guinea Pig

“…In fact, it has been shown to significantly eradicate Staphylococcus sp [14, 23, 24], Pseudomonas sp 6 , or Candida sp [25]. Many studies have also shown the efficacy of PDT using in vivo models.…”

“…This method is more widely used for oral pathologies [10], but its application in the otologic field remains to be defined. Many studies have demonstrated the efficacy of photodynamic antimicrobial chemotherapy using methylene blue as a photosensitizer [11-13] including effectiveness against most common pathogens found in chronic otitis, such as Staphylococcus aureus or Pseudomonas aeruginosa [9, 14-16]. …”

Application of an active attachment model as a high-throughput demineralization biofilm model

“…When activated by light, it transfers energy to molecular oxygen, resulting in production of reactive oxygen species including singlet oxygen, superoxide ions, hydroxyls, and other free radicals that lead to direct damage of cellular components. 18,19 The advantages of PACT were discussed in a recent review 20 : it is equally effective against antibioticresistant and antibiotic-susceptible bacteria. The development of resistance to PACT appears to be unlikely, since, in microbial cells, singlet oxygen and free radicals interact with several cell structures and different metabolic pathways.…”