Photodynamic Therapy With Propolis: Antibacterial Effects on Staphylococcus aureus, Streptococcus mutans and Escherichia coli Analysed by Atomic Force Microscopy

• Published in: Journal of lasers in medical sciences Vol. 11; no. Suppl 1; pp. S107 - S112
• Main Authors: Fonseca, Alice de Morais Veras, Sampaio, Guilherme Herbet Leite, Araujo, Wládia Pontes, da Silva, Raí Emanuel, Ribeiro, Fábio de Oliveira Silva, Brito, Manoel da Paixão, Sousa, Francisca Beatriz de Melo, Torres, Amanda Azevedo, Araújo, Alyne Rodrigues, Pinto, Antonione Santos Bezerra
• Format: Journal Article
• Language: English
• Published: Iran Laser Application in Medical Sciences Research Center 2020
• Subjects: Original; Antimicrobial activity; Propolis; Photodynamic therapy
• ISSN: 2008-9783; 2228-6721
• DOI: 10.34172/JLMS.2020.S17

Photodynamic therapy (PDT) is a process that uses a light source (e.g. laser), oxygen molecules and a photosensitizing agent. PDT aims to act against pathogens, including those resistant to antimicrobials. The association of PDT with natural drugs, such as Propolis, has not been widely studied.
Therefore, this study aimed to evaluate the antimicrobial effect of PDT in vitro by using Propolis as a photosensitizing agent. For this purpose, the dry Propolis extract was used as a photosensitizer and a low-power laser (Photon Laser III model) was irradiated onto the microwells for 90 seconds. Gram-positive and Gram-negative bacterial strains were used in the tests at a concentration of 5 × 10
CFU/mL. Initially, the antibacterial activity of the photosensitizers without laser action was determined by using a serial microdilution method before the experiment with a laser. After the incubation of the plates in a bacteriological oven, resazurin (0.1%) was added and the minimum inhibitory concentration (MIC) was determined. Alterations in the morphology of the bacteria were analysed by using atomic force microscopy (AFM).
Bacteria were sensitive to Propolis with MICs ranging from 13.75 to 0.85 mg/mL, but no susceptibility was observed for methylene blue without laser application. A change was observed for MIC values of Propolis against
after irradiation, which decreased from 1.71 mg/mL to 0.85 mg/mL. However, this behaviour was not observed in
, the only gram-negative strain used. In addition, AFM images revealed alterations in the size of one of the bacteria tested.
The Propolis is more active against gram-positive bacteria and PDT improved its activity against one of the strains tested.