Comparison of the photodynamic fungicidal efficacy of methylene blue, toluidine blue, malachite green and low-power laser irradiation alone against Candida albicans

Abstract

This study was to evaluate specific effects of photodynamic therapy (energy density 15.8 J/cm(2), 26.3 J/cm(2) and 39.5 J/cm(2)) using methylene blue, toluidine blue and malachite green as photosensitizers and low-power laser irradiation on the viability of Candida albicans. Suspensions of C. albicans containing 10(6) cells/ml were standardized in a spectrophotometer. For each dye, 120 assays, divided into four groups according to the following experimental conditions, were carried out: laser irradiation in the presence of the photosensitizer; laser irradiation only; treatment with the photosensitizer only; no exposure to laser light or photosensitizer. Next, serial dilutions were prepared and seeded onto Sabouraud dextrose agar for the determination of the number of colony-forming units per milliliter (CFU/ml). The results were subjected to analysis of variance and the Tukey test (P < 0.05). Photodynamic therapy using the photosensitizers tested was effective in reducing the number of C. albicans.. The number of CFU/ml was reduced by between 0.54 log(10) and 3.07 log(10) and depended on the laser energy density used. Toluidine blue, methylene blue and malachite green were effective photosensitizers in antimicrobial photodynamic therapy against C. albicans, as was low-power laser irradiation alone.

Photoinactivation of Candida albicans using methylene blue as photosensitizer

“…The studies of Dai et al 1 , Kato et al 4 , Teichert et al 6 , Pereira et al 7 , Souza et al 8 , Queiroga et al 9 , Munin et al 10 , Silva Martins et al 17 , Giroldo et al 22 and Souza et al 23 , investigated the effects of photodynamic therapy on the viability of Candida albicans using methylene blue as a photosensitizer. The results of these studies proved the antifungal effect of this treatment modality.…”

“…This methodology has been widely used in researches that assessed the antimicrobial effect of PDT on microorganism in plankton form from a cell suspension 9,10,23 .…”

Mixed biofilms formed by C. albicans and non-albicans species: a study of microbial interactions

“…7 A major attribute of the Candida genus virulence is its ability to form surface-attached microbial communities known as biofilms. 8,9 In general, biofilm development evolves according to four sequential steps: first, adhesion of microorganisms to a surface; second, discrete colony formation and organization of cells; third, secretion of extracellular polysaccharides (EPS) and maturation into a three-dimensional structure; and, fourth, dissemination of progeny biofilm cells. 10 The extracellular matrix of the biofilm can protect the cells from phagocytosis, maintain the integrity of the biofilm, and limit the diffusion of substances.…”

“…3 Bacteria are commonly associated with Candida in the polymicrobial biofilms found in medical devices. 8 Harriot and Noverr 17 studied the interactions in polymicrobial biofilms formed by C. albicans and Staphylococcus aureus in an in vitro model, and observed a synergistic relationship between the two species. On the other hand, Tampakakis et al 18 analyzed an in vivo interaction between the species C. albicans and the Gram-negative Salmonella typhimurium.…”

Comparison of the hemolytic activity between C. albicans and non-albicans Candida species

“…Candida albicans is the most pathogenic Candida species and is frequently identified in candidiasis lesions in humans. 1 Twenty years ago, C. albicans represented 80% of the Candida species recovered from patients with oral and systemic candidiasis. Although C. albicans continues to be the most frequently isolated species, the number of infections caused by non-albicans species has increased significantly over the last two decades.…”