Study of photodynamic therapy in the control of isolated microorganisms from infected wounds—an in vitro study

Abstract

The effective treatment of infected wounds continues to be a serious challenge, mainly due to the rise of antibiotic-resistant bacteria. Photodynamic therapy (PDT) refers to the topical or systemic administration of a non-toxic, photosensitizing agent (PS), followed by irradiation with visible light of a suitable wavelength. The possibility of applying the PDT locally is what makes it so favorable to the treatment of infected wounds. The goal of this study was to evaluate the action of the PDT in the inactivation in vitro of microorganisms coming from infected wounds, using methylene blue (MB) and photodithazine (PDZ) as the PS and comparing the efficacy of these two compounds for PDT on bacteria. For the application of PDT, isolated microorganisms identified from material collected from wounds were suspended in a saline solution containing 10(6) viable cells/ml. Each isolated microorganism was submitted to PDT with MB and with PDZ in accordance with the following treatment groups: N/T--no treatment; T1--PDT with PDZ; T2--PDT with MB; T3--irradiation without PS; T4--treatment with PDZ without light; and T5--treatment with MB without light. As a light source, an LED-based device was used (Biopdi/Irrad-Lead 660), composed of 54 LEDs, each with 70 mW of power in the 660 nm region of the electromagnetic spectrum. Each tray of 96 wells was irradiated with an intensity of 25 mW/cm(2) and a dose of light of 50 J/cm(3) for 33 min. All the tests were made in duplicate. It was then concluded that the PDT with PDZ was capable of inhibiting the growth of gram-positive bacteria samples, however it did not have the same effect on gram-negative bacteria, which showed growth greater than 100,000 CFU; the PDT with MB showed an effectiveness on gram-positive as well as gram-negative bacteria, for it was able to inhibit bacterial growth in both cases.

The role of the light source in antimicrobial photodynamic therapy

“…The tested microorganisms were mostly obtained from American Type Culture Collection but in some cases pathogens, especially S. aureus , were isolants or clinical strains (Table 1). 60,195,210,211,251,363,421,461 Several studies focused on APDT of oral microflora, in particular, bacteria found in dentin, usually isolated from patients with deep caries lesions 153,216,257,263,282,284,362,385…”

“…The tested microorganisms were mostly obtained from American Type Culture Collection but in some cases pathogens, especially S. aureus, were isolants or clinical strains (Table 1). 60,195,210,211,251,363,421,461 Several studies focused on APDT of oral microflora, in particular, bacteria found in dentin, usually isolated from patients with deep caries lesions 153,216,257,263,282,284,362,385 Some studies also investigated MB-APDT targeted towards viruses, including vesicular stomatitis virus (VSV), bovine viral diarrhea virus (BVDV), dengue virus, West Nile virus (WNV), hepatitis C virus (HCV), herpes simplex virus type 1 (HSV-1) and SARS-CoV2. 215,297,299,300,311,314,321,331,403,408,409,411 Anti-parasitic photodynamic therapy investigations were dominated by Leishmania spp.…”

Utilização de terapia fotodinâmica e óleos essenciais no controle In Vitro de <em>Acinetobacter Baumannii</em> e <em>Pseudomonas Aeruginosa</em>

“…Além da própria resistência intrínseca de cepas bacterianas a formação de espécies reativas de oxigênio, o comprimento de onda, intensidade de luz e fotossensibilizador utilizado, interferem ativamente em tal processo. [17][18][19] Por fim, foi possível notar que caso a quantidade de FS não seja suficiente para interação completa das bactérias existente no meio, a exposição isolada à fonte de energia pode causar efeito contrário e estimular a formação de novas colônias. Tal fato, quando avaliado isoladamente, pode causar desestimulo a sua utilização.…”

Improving the Management and Treatment of Diabetic Foot Infection: Challenges and Research Opportunities

“…As PSs can potentially bind to many sites in the bacteria cell, the lethal oxidative damage caused by PDT is non-specific. This is important for activity against AMR pathogens and greatly reduces the likelihood of developing resistance, as confirmed by several laboratory experiments [ 93 , 94 , 95 ]. In addition, anionic or neutral PS also damage DNA strands, lowering thymidine incorporation during DNA synthesis [ 96 ].…”