Antimicrobial Photodynamic Therapy: Photodynamic Antimicrobial Effects of Malachite Green on Staphylococcus, Enterobacteriaceae, and Candida

Objective: This study investigated in vitro the photodynamic antimicrobial effects of the photosensitizer malachite green on clinical strains of Staphylococcus , Enterobacteriaceae, and Candida . Materials and Methods: Thirty-six microbial strains isolated from the oral cavity of patients undergoing prolonged antibiotic therapy, including 12 Staphylococcus , 12 Enterobacteriaceae, and 12 Candida strains, were studied. The number of cells of each microorganism was standardized to 10 6 cells/mL. Twenty-four assays were carried out for each strain according to the following experimental conditions: gallium-aluminum-arsenide laser and photosensitizer ( n = 6, L+P+), laser and physiologic solution ( n = 6, L+P−), photosensitizer ( n = 6, L−P+), and physiologic solution ( n = 6, L−P−). Next, cultures were prepared on brain–heart infusion agar for the growth of Staphylococcus and Enterobacteriaceae, and on Sabouraud dextrose agar for the growth of Candida, and incubated for 48 h at 37°C. The results are reported as the number of colony-forming units (CFU/mL) and were analyzed with analysis of variance and the Tukey test. Results: The Staphylococcus, enterobacterial, and Candida strains were sensitive to photodynamic therapy with malachite green (L+P+). A reduction of ∼7 log 10 for Staphylococcus , 6 log 10 for enterobacteria, and 0.5 log 10 for the genus Candida . Significant statistical differences were observed between the L+P+ groups and the control groups (L−P−). Conclusion: The Staphylococcus , Enterobacteriaceae, and Candida strains studied were sensitive to photodynamic therapy with malachite green.