Evaluation of bacterial reduction and resistance after multiple cycles of photodynamic therapy.

Author(s)

Lucas Henrique de Paula Zago

• Document type: Doctoral Thesis
• Press: Araraquara. 2019-02-25.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Farmacêuticas. Araraquara
• Defense date: 2018-12-17
• Advisor: Carla Raquel Fontana

Abstract

Periodontal disease is an infectious-inflammatory pathological process, which can cause eventual loss of the dental element. The main treatment is scaling and root planing (RAR), which, although effective, has as a limiting factor the technical difficulty of intervening in biofilms of difficult access areas. Associations with antibiotics can cause side effects and in resistant bacteria they may be ineffective. In this way, antimicrobial photodynamic therapy (aPDT) appears as an adjuvant option for the treatment of periodontal diseases. This study investigated, in vitro, the potential for reduction and development of bacterial resistance in a clinical pool, resistant to metronidazole, against multiple cycles of aPDT in planktonic phase and biofilm using methylene blue, chlorine-e6 and curcumin as photosensitizers (PS). For resistance induction cycles, it was necessary to find the sub optimal conditions of the aPDT, by quantifying the colonies formed per milliliter of sample (CFU/mL). The following parameters were found in the planktonic phase: 50 μg/mL methylene blue and light dose of 120 J/cm2 with a reduction of 1.67 log10, chlorine-e6 and curcumina obtained reductions of 1.91 log10 and 1.76 log10, respectively, with light dose of 25 J/cm2 and 100 μg/mL PS. Subsequently, the pool of bacteria was subjected to multiple exposures of aPDT, followed by a recovery period, in which surviving bacterial cells were resuspended in the same treatment, and so on until resistance development was observed or up to the limit of 15 cycles. For methylene blue and chlorine-e6, the microorganisms were completely eliminated at the end of the 5th cycle and for curcumin at the end of the third cycle. In biofilm, the sub optimal dose of methylene blue aPDT was 150 μg/mL + 150 J/cm2 with a reduction of 2.53 log10. For chlorine-e6 and curcumin the sub optimal dose was 150 J/cm2 associated with 100 μg/mL of each PS, with respective reductions: 1.47 log10; 1.88 log10. Fifteen cycles of aPDT were applied, which although not completely reducing the microbial load, were able to promote a significant increase in bacterial death. The results indicate that aPDT may be a promising adjuvant approach in the treatment of periodontal disease. (AU)

• FAPESP's process: 16/10310-5 - Bacterial reduction and resistance after multiple cycles of photodynamic therapy
• Grantee: Lucas Henrique de Paula Zago
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)