Author/Authors :
de Morais Veras da Fonseca, Alice Exact and Health Sciences of Piauí of the Institute of Higher Education of Vale do Parnaíba, Parnaíba, PI, Brazil , Herbet Leite Sampaio, Guilherme Exact and Health Sciences of Piauí of the Institute of Higher Education of Vale do Parnaíba, Parnaíba, PI, Brazil , Pontes Araujo, Wládia Exact and Health Sciences of Piauí of the Institute of Higher Education of Vale do Parnaíba, Parnaíba, PI, Brazil , Emanuel da Silva, Raí Biodiversity and Biotechnology Research Center (BIOTEC) - Federal University of Piauí, Parnaíba, PI, Brazil , de Oliveira Silva Ribeiro, Fábio Biodiversity and Biotechnology Research Center (BIOTEC) - Federal University of Piauí, Parnaíba, PI, Brazil , da Paixão Brito, Manoel Biodiversity and Biotechnology Research Center (BIOTEC) - Federal University of Piauí, Parnaíba, PI, Brazil , Beatriz de Melo Sousa,Francisca Biodiversity and Biotechnology Research Center (BIOTEC) - Federal University of Piauí, Parnaíba, PI, Brazil , Azevedo Torres, Amanda University of Piauí, Parnaíba, PI, Brazil , Rodrigues de Araújo, Alyne Biodiversity and Biotechnology Research Center (BIOTEC) - Federal University of Piauí, Parnaíba, PI, Brazil , Santos Bezerra Pinto, Antonione Medical Professor at the Faculty of Human - Exact and Health Sciences of Piauí of the Institute of Higher Education of Vale do Parnaíba, Parnaíba, PI, Brazil
Abstract :
Introduction: 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.
Methods: 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 × 105
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).
Results: 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 Staphylococcus aureus after irradiation, which decreased from
1.71 mg/mL to 0.85 mg/mL. However, this behaviour was not observed in Escherichia coli, the only
gram-negative strain used. In addition, AFM images revealed alterations in the size of one of the
bacteria tested.
Conclusion: The Propolis is more active against gram-positive bacteria and PDT improved its activity
against one of the strains tested.
