In vitro evaluation of the cis-[Ru(phen)2(pPDIp)]2+⁎⁎ complex for antimicrobial photodynamic therapy against Sporothrix brasiliensis and Candida albicans

BACKGROUND

Photodynamic therapy (PDT) activates a photosensitizer by visible light to generate cytotoxic oxygen species that lead to cell death. With proper illumination, PDT is often used in applications on superficial and sub-surface lesions. Sporotrichosis infection occurs by Sporothrix fungi which causes a skin wound, worsened by Candida albicans infections. This study investigated the photosensitizing efficiency of the Ru(phen)₂(pPDIp)(PF₆)₂ complex, RupPDIp, against S. brasiliensis and C. albicans.

MATERIAL AND METHODS

RupPDIp efficiency against these fungi was tested using 450 nm (blue light and 36 J/cm²) and 525 nm (green light, 25.2 J/cm²) at 0.05-20 μM concentrations. To ensure PDT effectiveness, control groups were tested in the absence and in the presence of RupPDIp under light irradiation and in the dark.

RESULTS

RupPDIp eliminated both fungi at ≤5.0 μM. Green light showed the best results, eliminating S. brasiliensis and C. albicans colonies at RupPDIp 0.5 μM and 0.05 μM, respectively.

CONCLUSION

RupPDIp is a promising photosensitizer in aPDT, eliminating 10⁶ CFU/mL of both fungi at 450 nm and 525 nm, with lower light doses and concentrations when treated with the green light compared to the blue light.

Analyzing efficacy and safety of anti-fungal blue light therapy via kernel-based modeling the reactive oxygen species induced by light

OBJECTIVE

The goal of this study is to investigate the efficacy, safety, and mechanism of ABL for inactivating Candida albicans (C. albicans), and to determine the best wavelength for treating candida infected disease, by experimental measurements and dynamic modeling.

METHODS

The changes in reactive oxygen species (ROS) in C. albicans and human host cells under the irradiation of 385, 405, and 415nm wavelengths light with irradiance of 50mW/cm2 were measured. Moreover, a kernel-based nonlinear dynamic model, i.e., nonlinear autoregressive with exogenous inputs (NARX), was developed and applied to predict the concentration of light-induced ROS, whose kernels were selected by a newly developed algorithm based on particle swarm optimization (PSO).

RESULTS

The ROS concentration was increased respectively about 10-12 times in C. albicans and about 3-6 times in human epithelial cells by the ABL treatment with the same fluence of 90J/cm2. The NARX models were respectively fitted to the data from the experiments on both types of cells. Besides, four different kernel functions, including Gaussian, Laplace, linear and polynomial kernels, were compared in their fitting accuracies. The errors with the Laplace kernel turned out to be only 0.2704 and 0.0593, as respectively fitted to the experimental data of the C. albicans and human host cells.

CONCLUSION

The results demonstrated the effectiveness of the NARX modeling approach, and revealed that the 415nm light was more effective as an anti-fungal treatment with less damage to the host cells than the 405 or 385nm light.

SIGNIFICANCE

The kernel-based NARX model identification algorithm offers opportunities for determining the effective and safe light dosages in treating various fungal infection diseases.

Hybrid UV-C/microfiltration process in membrane photoreactor for wastewater disinfection

A novel hybrid UV-C/microfiltration process for water disinfection is presented, and its application in continuous mode operation to the removal of different pathogen germs (Escherichia coli, Enterococcus faecalis, and Candida albicans) present in urban wastewater. The membrane photoreactor is based on porous stainless steel membranes coated with a TiO₂ layer and illuminated by a UV-C lamp (254 nm). A valve actuator in the outlet of the UV-C stream allows operation of the system under conditions of constant transmembrane pressure (TMP) keeping the UV-C contact time in few seconds, significantly lower than the typical irradiation time employed in TiO₂ photocatalytic processes. An E. coli removal of up to 4-log in the permeate stream and up to 2-log in the UV-C outlet was achieved with a 0.2 μm membrane operating with a TMP of 0.5 bar and a UV-C contact time as low as 8 s. The microbial balance data from the cells recovered from the membrane confirmed that 96-98% of the removed microorganisms died due to the UV-C action over the membrane surface. Modification of the membrane with a TiO₂ layer has been also shown to be a suitable way to improve both the UV-C inactivation and the filtration efficiency. The results reported in this work constitute a proof of concept of the synergy between UV-C and filtration that can be achieved in a hybrid UV-C/microfiltration system, being a good example of process intensification where two products of different quality can be simultaneously obtained.

Amphiphilic tetracationic porphyrins are exceptionally active antimicrobial photosensitizers: In vitro and in vivo studies with the free-base and Pd-chelate

Antimicrobial photodynamic inactivation (aPDI) employs the combination of nontoxic photosensitizing dyes and visible light to kill pathogenic microorganisms regardless of drug-resistance, and can be used to treat localized infections. A meso-substituted tetra-methylpyridinium porphyrin with one methyl group replaced by a C12 alkyl chain (FS111) and its Pd-derivative (FS111-Pd) were synthesized and tested as broad-spectrum antimicrobial photosensitizers when excited by blue light (5 or 10 J/cm² ). Both compounds showed unprecedented activity, with the superior FS111-Pd giving 3 logs of killing at 1 nM, and eradication at 10 nM for Gram-positive methicillin-resistant Staphylococcus aureus. For the Gram-negative Escherichia coli, both compounds produced eradication at 100 nM, while against the fungal yeast Candida albicans, both compounds produced eradication at 500 nM. Both compounds could be categorized as generators of singlet oxygen (Φ_Δ = 0.62 for FS111 and 0.71 for FS111-Pd). An in vivo study was carried out using a mouse model of localized infection in a partial thickness skin abrasion caused by bioluminescent Gram-negative uropathogenic E. coli. Both compounds were effective in reducing bioluminescent signal in a dose-dependent manner when excited by blue light (405 nm), but aPDI with FS111-Pd was somewhat superior both during light and in preventing recurrence during the 6 days following PDT.

Photodynamic Inactivation Potentiates the Susceptibility of Antifungal Agents against the Planktonic and Biofilm Cells of Candida albicans

Photodynamic inactivation (PDI) has been shown to be a potential treatment modality against Candida infection. However, limited light penetration might leave some cells alive and undergoing regrowth. In this study, we explored the possibility of combining PDI and antifungal agents to enhance the therapeutic efficacy of Candida albicans and drug-resistant clinical isolates. We found that planktonic cells that had survived toluidine blue O (TBO)-mediated PDI were significantly susceptible to fluconazole within the first 2 h post PDI. Following PDI, the killing efficacy of antifungal agents relates to the PDI dose in wild-type and drug-resistant clinical isolates. However, only a 3-log reduction was found in the biofilm cells, suggesting limited therapeutic efficacy under the combined treatment of PDI and azole antifungal drugs. Using confocal microscopic analysis, we showed that TBO-mediated PDI could partially remove the extracellular polymeric substance (EPS) of biofilm. Finally, we showed that a combination of PDI with caspofungin could result in the complete killing of biofilms compared to those treated with caspofungin or PDI alone. These results clearly indicate that the combination of PDI and antifungal agents could be a promising treatment against C. albicans infections.

An in Vitro Study on the Effect of Combined Treatment with Photodynamic and Chemical Therapies on Candida albicans

Candida albicans is the most commonly encountered human fungal pathogen, and it is traditionally treated with antimicrobial chemical agents. The antimicrobial effect of these agents is largely weakened by drug resistance and biofilm-associated virulence. Enhancement of the antimicrobial activity of existing agents is needed for effective candidiasis treatment. Our aim was to develop a therapy that combined biofilm disruption with existing antimicrobial agents. Photodynamic therapy (PDT) utilizing curcumin and blue light was tested as an independent therapy and in combination with fluconazole treatment. Viability assays and morphology analysis were used to assess the effectiveness of C. albicans treatment. Results showed that fluconazole treatment decreased the viability of planktonic C. albicans, but the decrease was not as pronounced in adherent C. albicans because its biofilm form was markedly more resistant to the antimicrobiotic. PDT effectively eradicated C. albicans biofilms, and when combined with fluconazole, PDT significantly inhibited C. albicans to a greater extent. This study suggests that the addition of PDT to fluconazole to treat C. albicans infection enhances its effectiveness and can potentially be used clinically.

Light-driven photosensitizer uptake increases Candida albicans photodynamic inactivation

Photodynamic Inactivation (PDI) is based on the use of a photosensitizer (PS) and light that results mainly in the production of reactive oxygen species, aiming to produce microorganism cell death. PS incubation time and light dose are key protocol parameters that influence PDI response; the correct choice of them can increase the efficiency of inactivation. The results of this study show that a minor change in the PDI protocol, namely light-driven incubation leads to a higher photosensitizer and more uniform cell uptake inside the irradiated zone. Furthermore, as the uptake increases, the damage caused by PDI also increases. The proposed light-driven incubation prior to the inactivation illumination dose has advantages when compared to the traditional PDI treatments since it can be more selective and effective. Using a violet light as pre-illumination (light-driven incubation) source and a red-light system as PDI source, it was possible to demonstrate that when compared to the traditional protocol of dark incubation, the pre-illuminated cell culture showed an inactivation increase of 7 log units. These in vitro results performed in Candida albicans cells may result in the introduction of a new protocol for PDI.

Properties of halogenated and sulfonated porphyrins relevant for the selection of photosensitizers in anticancer and antimicrobial therapies

The impact of substituents on the photochemical and biological properties of tetraphenylporphyrin-based photosensitizers for photodynamic therapy of cancer (PDT) as well as photodynamic inactivation of microorganisms (PDI) was examined. Spectroscopic and physicochemical properties were related with therapeutic efficacy in PDT of cancer and PDI of microbial cells in vitro. Less polar halogenated, sulfonamide porphyrins were most readily taken up by cells compared to hydrophilic and anionic porphyrins. The uptake and PDT of a hydrophilic porphyrin was significantly enhanced with incorporation in polymeric micelles (Pluronic L121). Photodynamic inactivation studies were performed against Gram-positive (S. aureus, E. faecalis), Gram-negative bacteria (E. coli, P. aeruginosa, S. marcescens) and fungal yeast (C. albicans). We observed a 6 logs reduction of S. aureus after irradiation (10 J/cm²) in the presence of 20 μM of hydrophilic porphyrin, but this was not improved with incorporation in Pluronic L121. A 2–3 logs reduction was obtained for E. coli using similar doses, and a decrease of 3–4 logs was achieved for C. albicans. Rational substitution of tetraphenylporphyrins improves their photodynamic properties and informs on strategies to obtain photosensitizers for efficient PDT and PDI. However, the design of the photosensitizers must be accompanied by the development of tailored drug formulations.

Microwave radiation is effective at disinfecting dental stone surfaces without changing their physical properties

The aims of this study were to evaluate the effectiveness of different microwave radiation regimens for disinfection of type IV dental stone surfaces and to assess the influence of these regimens on surface roughness and dimensional change following disinfection. Three hundred cylindrical (20 × 2-mm) test specimens were made in type IV stone and divided into subgroups of 20 according to the microorganisms tested (Staphylococcus aureus, Escherichia coli, or Candida albicans) and the 900-W microwave radiation protocol (cycles of 3, 5, or 7 minutes; a positive control; or a negative control). To test physical changes, 80 test specimens were made with the same dimensions except that they had 2 parallel and symmetrical indentations measuring 8 × 4 mm. These specimens were divided into 4 subgroups of 20 each (a subgroup for each radiation time and a negative control). The mean dimensional change and roughness data were analyzed by mixed models for repeated measures and Tukey-Kramer tests. Disinfection was analyzed with descriptive statistics. For E coli and C albicans, all radiation times proved effective at sterilizing the test specimens. For S aureus, sterilization was achieved with 5 and 7 minutes of exposure; however, colonies were observed in 10 Petri dishes (50%) exposed to 3 minutes of microwave radiation. No statistically significant difference in dimensional change or surface roughness was observed for any radiation regimen (P > 0.05).

Comparison of Riboflavin and Toluidine Blue O as Photosensitizers for Photoactivated Disinfection on Endodontic and Periodontal Pathogens In Vitro

Photoactivated disinfection has a strong local antimicrobial effect. In the field of dentistry it is an emerging adjunct to mechanical debridement during endodontic and periodontal treatment. In the present study, we investigate the effect of photoactivated disinfection using riboflavin as a photosensitizer and blue LED light for activation, and compare it to photoactivated disinfection with the widely used combination of toluidine blue O and red light. Riboflavin is highly biocompatible and can be activated with LED lamps at hand in the dental office. To date, no reports are available on the antimicrobial effect of photoactivated disinfection using riboflavin/blue light on oral microorganisms. Planktonic cultures of eight organisms frequently isolated from periodontal and/or endodontic lesions (Aggregatibacter actinomycetemcomitans, Candida albicans, Enterococcus faecalis, Escherischia coli, Lactobacillus paracasei, Porphyromonas gingivalis, Prevotella intermedia and Propionibacterium acnes) were subjected to photoactivated disinfection with riboflavin/blue light and toluidine blue O/red light, and survival rates were determined by CFU counts. Within the limited irradiation time of one minute, photoactivated disinfection with riboflavin/blue light only resulted in minor reductions in CFU counts, whereas full kills were achieved for all organisms when using toluidine blue O/red light. The black pigmented anaerobes P. gingivalis and P. intermedia were eradicated completely by riboflavin/blue light, but also by blue light treatment alone, suggesting that endogenous chromophores acted as photosensitizers in these bacteria. On the basis of our results, riboflavin cannot be recommended as a photosensitizer used for photoactivated disinfection of periodontal or endodontic infections.

Photodynamic Inactivation of Candida albicans with Imidazoacridinones: Influence of Irradiance, Photosensitizer Uptake and Reactive Oxygen Species Generation

The increasing applicability of antifungal treatments, the limited range of available drug classes and the emergence of drug resistance in Candida spp. suggest the need for new treatment options. To explore the applicability of C. albicans photoinactivation, we examined nine structurally different imidazoacridinone derivatives as photosensitizing agents. The most effective derivatives showed a >10(4)-fold reduction of viable cell numbers. The fungicidal action of the three most active compounds was compared at different radiant powers (3.5 to 63 mW/cm2), and this analysis indicated that 7 mW/cm2 was the most efficient. The intracellular accumulation of these compounds in fungal cells correlated with the fungicidal activity of all 9 derivatives. The lack of effect of verapamil, an inhibitor targeting Candida ABC efflux pumps, suggests that these imidazoacridinones are not substrates for ABC transporters. Thus, unlike azoles, a major class of antifungals used against Candida, ABC transporter-mediated resistance is unlikely. Electron paramagnetic resonance (EPR)-spin trapping data suggested that the fungicidal light-induced action of these derivatives might depend on the production of superoxide anion. The highest generation rate of superoxide anion was observed for 1330H, 1610H, and 1611. Singlet oxygen production was also detected upon the irradiation of imidazoacridinone derivatives with UV laser light, with a low to moderate yield, depending on the type of compound. Thus, imidazoacridinone derivatives examined in the present study might act via mixed type I/type II photodynamic mechanism. The presented data indicate lack of direct correlation between the structures of studied imidazoacridinones, cell killing ability, and ROS production. However, we showed for the first time that for imidazoacridinones not only intracellular accumulation is necessary prerequisite of lethal photosensitization of C. albicans, but also localization within particular cellular structures. Our findings present IA derivatives as efficient antifungal photosensitizers with a potential to be used in local treatment of Candida infection.

Irreversible electropermeabilization of the human pathogen Candida albicans: an in-vitro experimental study

Pathogenic fungi cause many life-threatening infections, especially among individuals with immune system dysfunction. The antifungal drugs commonly used to suppress fungal pathogens can result in long-lasting and toxic therapy. In this work, irreversible electropermeabilization was used to investigate the dynamics of the decrease in Candida albicans colony vitality after application of a pulsed electric field (PEF) and use of antifungal drugs. The fungi were subjected to single 250-µs to 2-ms (0.5-2.5 kV/cm) pulses or repeated short 5-µs pulses, and efficacy was compared. It was shown that electropermeabilization combined with antifungal agents results in rapid and more effective treatment, eliminating more than 90% of C. albicans colony-forming units in a single procedure, which is advantageous in biomedicine. It was also observed that, because of application of PEF and use of the antifungal agents, the Candida cells form cell aggregates and average live cell size is reduced by as much as 53%.

Real-time evaluation of two light delivery systems for photodynamic disinfection of Candida albicans biofilm in curved root canals

Antimicrobial photodynamic therapy (APDT) combined with endodontic treatment has been recognized as an alternative approach to complement conventional root canal disinfection methods on bacterial biofilms. We developed an in  vitro model of bioluminescent Candida albicans biofilm inside curved dental root canals and investigated the microbial reduction produced when different light delivery methods are employed. Each light delivery method was evaluated in respect to the light distribution provided inside curved root canals. After conventional endodontic preparation, teeth were sterilized before canals were contaminated by a bioluminescent strain of C. albicans (CEC789). Methylene blue (90 μM) was introduced into the canals and then irradiated (λ = 660 nm, P = 100 mW, beam diameter = 2 mm) with laser tip either in contact with pulp chamber or within the canal using an optical diffuser fiber. Light distribution was evaluated by CCD camera, and microbial reduction was monitored through bioluminescence imaging. Our findings demonstrated that the bioluminescent C. albicans biofilm model had good reproducibility and uniformity. Light distribution in dental tissue was markedly dependent on the light delivery system, and this strategy was directly related to microbial destruction. Both light delivery systems performed significant fungal inactivation. However, when irradiation was performed with optical diffuser fiber, microbial burden reduction was nearly 100 times more effective. Bioluminescence is an interesting real-time analysis to endodontic C. albicans biofilm inactivation. APDT showed to be an effective way to inactivate C. albicans biofilms. Diffuser fibers provided optimized light distribution inside curved root canals and significantly increased APDT efficiency.

Photophysicochemical behavior and antimicrobial activity of dihydroxosilicon tris(diaquaplatinum)octacarboxyphthalocyanine

Platination of dihydroxosilicon octacarboxyphthalocyanine (OH)2SiOCPc was successfully carried out to give dihydroxosilicon tris(diaquaplatinum)octacarboxyphthalocyanine (OH)2SiOCPc(Pt)3 conjugate. Slight blue shifting of the absorption spectrum of (OH)2SiOCPc(Pt)3 was observed on conjugation with platinum. Comparative photophysicochemical behavior and antimicrobial photo-activities of (OH)2SiOCPc(Pt)3 conjugate with (OH)2SiOCPc or Pt nanoparticles revealed that the heavy atom, Pt on the periphery of the phthalocyanine significantly enhanced its singlet oxygen generation with a quantum yield of 0.56 obtained for the (OH)2SiOCPc(Pt)3 conjugate. The (OH)2SiOCPc(Pt)3 conjugate showed highest antimicrobial activity towards Candida albicans and Escherichia coli compared to (OH)2SiOCPc and Pt nanoparticles alone under illumination.

Antimicrobial photodynamic inactivation inhibits Candida albicans virulence factors and reduces in vivo pathogenicity

The objective of this study was to evaluate whether Candida albicans exhibits altered pathogenicity characteristics following sublethal antimicrobial photodynamic inactivation (APDI) and if such alterations are maintained in the daughter cells. C. albicans was exposed to sublethal APDI by using methylene blue (MB) as a photosensitizer (0.05 mM) combined with a GaAlAs diode laser (λ 660 nm, 75 mW/cm(2), 9 to 27 J/cm(2)). In vitro, we evaluated APDI effects on C. albicans growth, germ tube formation, sensitivity to oxidative and osmotic stress, cell wall integrity, and fluconazole susceptibility. In vivo, we evaluated C. albicans pathogenicity with a mouse model of systemic infection. Animal survival was evaluated daily. Sublethal MB-mediated APDI reduced the growth rate and the ability of C. albicans to form germ tubes compared to untreated cells (P < 0.05). Survival of mice systemically infected with C. albicans pretreated with APDI was significantly increased compared to mice infected with untreated yeast (P < 0.05). APDI increased C. albicans sensitivity to sodium dodecyl sulfate, caffeine, and hydrogen peroxide. The MIC for fluconazole for C. albicans was also reduced following sublethal MB-mediated APDI. However, none of those pathogenic parameters was altered in daughter cells of C. albicans submitted to APDI. These data suggest that APDI may inhibit virulence factors and reduce in vivo pathogenicity of C. albicans. The absence of alterations in daughter cells indicates that APDI effects are transitory. The MIC reduction for fluconazole following APDI suggests that this antifungal could be combined with APDI to treat C. albicans infections.

Microwave irradiation as an alternative method for disinfection of denture base acrylic resins

AIM

This study evaluated the effect of microwave irradiation as an alternative method for disinfection of different types of denture base acrylic resins.

METHODS

Twenty-four samples for each conventional, microwaved and characterized heat-cured acrylic resin were made and subjected to sterilization with ethylene oxide for the groups: 1) irradiated samples; 2) non-irradiated samples; and 3) samples without yeast. Each group was subdivided according to inoculation with C. albicans, C. dubliniensis and C. tropicalis. The samples were inoculated with 100 µL of inoculum of each species of Candida and later placed in an incubator at 37 °C for 1 hr to perform the first adhesion. After this time, each well was supplemented with sterile media and the plate was once again taken to a stove for incubation at 37 °C for 6 hr. The samples were immersed in 100 mL of sterile water and irradiated with microwave at 650 W for 3 min. Control samples were considered as the non-irradiated group. After incubation for 48 hr, irradiated and non-irradiated samples were subjected to a digital colony counter.

RESULTS

Control group (non-irradiated) showed microbial growth for resins and the means of ufc/mL were without statistically significant differences. Microwave irradiated samples (experimental group) promoted no viable colonies for all Candida species and types of acrylic resins. The means of ufc/mL were without statistically significant differences.

CONCLUSION

Microwave irradiation was an effective method for disinfection of the acrylic resins inoculated with C. albicans, C. dubliniensis and C. tropicalis.

Calcofluor white combination antifungal treatments for Trichophyton rubrum and Candida albicans

Superficial mycoses caused by dermatophyte fungi are among the most common infections worldwide, yet treatment is restricted by limited effective drugs available, drug toxicity, and emergence of drug resistance. The stilbene fluorescent brightener calcofluor white (CFW) inhibits fungi by binding chitin in the cell wall, disrupting cell wall integrity, and thus entails a different mechanism of inhibition than currently available antifungal drugs. To identify novel therapeutic options for the treatment of skin infections, we compared the sensitivity of representative strains of the dermatophyte Trichophyton rubrum and Candida albicans to CFW and a panel of fluorescent brighteners and phytoalexin compounds. We identified the structurally related stilbene fluorescent brighteners 71, 85, 113 and 134 as fungicidal to both T. rubrum and C. albicans to a similar degree as CFW, and the stilbene phytoalexins pinosylvan monomethyl ether and pterostilbene inhibited to a lesser degree, allowing us to develop a structure-activity relationship for fungal inhibition. Given the abilities of CFW to absorb UV(365 nm) and bind specifically to fungal cell walls, we tested whether CFW combined with UV(365 nm) irradiation would be synergistic to fungi and provide a novel photodynamic treatment option. However, while both treatments individually were cytocidal, UV(365 nm) irradiation reduced sensitivity to CFW, which we attribute to CFW photoinactivation. We also tested combination treatments of CFW with other fungal inhibitors and identified synergistic interactions between CFW and some ergosterol biosynthesis inhibitors in C. albicans. Therefore, our studies identify novel fungal inhibitors and drug interactions, offering promise for combination topical treatment regimes for superficial mycoses.

Evaluation of UVB light efficacy for inducing apoptosis in Candida albicans cultures

BACKGROUND

Candida albicans is known as part of human's skin normal flora; but simultaneously, is the most common opportunistic fungal pathogen of human which can cause a variety of infections including cutaneous candidiasis. Because of the importance of superficial infections like cutaneous candidiasis, we tried to use Ultraviolet B light as a method of phototherapy for inducing apoptosis in irradiated colonies of Candida albicans.

MATERIALS AND METHODS

The Ultraviolet B with the wavelength of 302 nanometer was used for irradiating the colonies of Candida albicans. For detecting the eventual apoptotic reactions, the DNA of irradiated colonies as well as control colonies were extracted and then were run in 1% agarose gel electrophoresis containing ethidium bromide to observe luminescent DNA bands.

RESULTS

Despite irradiating of Ultraviolet B to yeast cells, no abnormalities including DNA laddering bands or smears were detected in bands formed by total genomic DNA.

DISCUSSION

The applied irradiation protocol in this investigation was not successful to induce apoptotic reactions in Ultraviolet-exposed colonies. Maybe, Heat shock proteins as the important part of fungal protein pool, inhibit the inducing pathway of apoptosis in irradiated colonies of Candida albicans.

Photodynamic therapy with Pc 4 induces apoptosis of Candida albicans

The high prevalence of drug resistance necessitates the development of novel antifungal agents against infections caused by opportunistic fungal pathogens, such as Candida albicans. Elucidation of apoptosis in yeast-like fungi may provide a basis for future therapies. In mammalian cells, photodynamic therapy (PDT) has been demonstrated to generate reactive oxygen species, leading to immediate oxidative modifications of biological molecules and resulting in apoptotic cell death. In this report, we assess the in vitro cytotoxicity and mechanism of PDT, using the photosensitizer Pc 4, in planktonic C. albicans. Confocal image analysis confirmed that Pc 4 localizes to cytosolic organelles, including mitochondria. A colony formation assay showed that 1.0 μM Pc 4 followed by light at 2.0 J cm(-2) reduced cell survival by 4 logs. XTT (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxyanilide) assay revealed that Pc 4-PDT impaired fungal metabolic activity, which was confirmed using the FUN-1 (2-chloro-4-[2,3-dihydro-3-methyl-(benzo-1,3-thiazol-2-yl)-methylidene]-1-phenylquinolinium iodide) fluorescence probe. Furthermore, we observed changes in nuclear morphology characteristic of apoptosis, which were substantiated by increased externalization of phosphatidylserine and DNA fragmentation following Pc 4-PDT. These data indicate that Pc 4-PDT can induce apoptosis in C. albicans. Therefore, a better understanding of the process will be helpful, as PDT may become a useful treatment option for candidiasis.

Susceptibility of Candida albicans to photodynamic therapy using methylene blue and toluidine blue as photosensitizing dyes

The increased resistance of Candida albicans to antibiotic therapy indicates the need for alternative treatments for oral candidiasis. Photodynamic therapy (PDT) has been researched as an alternative tool to inactivate pathogenic microorganisms. It uses a combination of a photosensitizer and a visible light source. This study evaluated the susceptibility of C. albicans to PDT and compared the efficacy of 100 microg/mL methylene blue (MB) and toluidine blue (TB) as photosensitizers. The light source was Indium-Gallium-Aluminum Phosphide (InGaAIP) laser at 53 J/cm2. Suspensions of 108 cells/mL of C. albicans were subject to PDT for 5 minutes in 96-well plates, then decimal dilutions were plated on Sabouraud Dextrose agar After 48h incubation at 37 degreesC, the number of CFU/mL were obtained and submitted to statistical analysis using Kolmogorov-Smirnov, ANOVA (p<0.0001) and Tukey tests. The results showed that MB or laser irradiation alone did not have statistically significant antifungal activity compared to the positive control group (p> 0. 05). Conversely, the number of viable C. albicans cells was reduced significantly after PDT using MB or mainly TB associated to diode laser irradiation. The data proved the efficacy of PDT against C. albicans cells, regardless of the photosensitizer used.

Role of the homologous recombination genes RAD51 and RAD59 in the resistance of Candida albicans to UV light, radiomimetic and anti-tumor compounds and oxidizing agents

We have cloned and characterized the RAD51 and RAD59 orthologs of the pathogenic fungus Candida albicans. CaRad51 exhibited more than 50% identity with several other eukaryotes and the conserved the catalytic domain of a bacterial RecA. As compared to the parental strain, null strains of rad51 exhibited a filamentous morphology, had a decreased grow rate and exhibited a moderate sensitivity to UV light, oxidizing agents, and compounds that cause double-strand breaks (DSB), indicating a role in DNA repair. By comparison, the rad52 null had a higher percentage of filaments, a more severe growth defect and a greater sensitivity to DNA-damaging compounds. Null strains of rad59 showed a UV-sensitive phenotype but behaved similarly to the parental strain in the rest of the assays. As compared to Saccharomyces cerevisiae, C. albicans was much more resistant to bleomycin and the same was true for their respective homologous recombination (HR) mutants. These results indicate that, as described in S. cerevisiae, RAD52 plays a more prominent role than RAD51 in the repair of DSBs in C. albicans and suggest the existence of at least two Rad52-dependent HR pathways, one dependent and one independent of Rad51.

Evaluation of the phototoxic potential of plants used in oriental medicine

AIM OF THE STUDY

Phototoxicity can be either harmful or beneficial. Yet the phototoxicity of oriental medicinal plants is an understudied area. The purpose of this study is to fill in this gap.

MATERIALS AND METHODS

The phototoxic potential of oriental medicinal plants was examined in vitro using photohemolysis and the Candida albicans test. Seventeen medicinal plants [Acorus gramineus (ACG), Panax ginseng C.A. (PAG), Platycodon grandiflorum (PLG), Aractylodes japonica (ATJ), Xanthium strumarium (XAS), Dioscorea batatas (DIB), Anemarrhena asphodeloides (ANA), Polygonatum sibiricum Red (PSR), Cocculus trilobus (COT), Ficus carica (FIC), Chelidonium majus var. asiaticum (CMA), Pulsatilla koreana (PUK), Agrimonia pilosa (AGP), Zanthoxylum schinifolium (ZAS), Angelica gigas (ANG), Ledebouriella seseloides (LES), and Cnidium officinale (CNO)] were selected because they showed strong fluorescence in one of our previous studies of 62 plants. We further evaluated in vivo phototoxicity in mice. 0.75 mL/kg of seed oil for Xanthium strumarium (XAS, ), or 1.25 mL/kg of extracted solutions of Atractylodes japonica (ATJ, ), Chelidonium majus var. asiaticum (CMA, ), Zanthoxylum schinifolium (ZAS, ), and Ledebouriella seseloides (LES, ) were given once, and evaluated for sunburn edema, formation of sunburn cell, decrease of epidermal Langerhans cells and local suppression of contact hypersensitivity by UVA irradiation.

RESULTS

Sixteen out of the 17 plants tested except COT showed significant photohemolysis, and 5 of those exhibited phototoxic killing of Candida albicans. The phototoxicity of oriental medicines using those 5 plants was then studied in mice. The 5 plants increased sunburn edema and formation of sunburn cell, and suppressed immune responses locally by decreasing epidermal Langerhans cells and contact hypersensitivity by UVA irradiation.

CONCLUSIONS

More than a quarter of oriental medicinal plants can be phototoxic, and strong fluorescence measured by absorption and fluorescence spectra can be an easier way to screen for phototoxicity. On the other hand, the phototoxicity of the plants may also be used therapeutically. Further studies regarding the phototoxicity of active components extracted from both live and dried oriental medicinal plants are necessary.

In vitro photodynamic properties of methylene blue in a combination with laser illumination at 630 nm concerning Candida albicans

The study had to define influence of combined applications of laser radiation and methylene blue (MB) on pathogenic culture of Candida albicans in vitro. The experimental study was done at standard techniques of method of cultivations in a broth. The laser irradiation of cultures was done at once after addition of MB in concentration 0.05%, 0.1% and 0.2%. During studying action of MB in dark, influence of MB to the growth of test-shtam without laser radiation, were prepared fluid Gissa's broth with glucose without Andrede's indicator. Activation of MB was done by laser with wave length 630 nm during 3 or 5 min. All experiments were passed in 4 parallels and 3 repeats. Maximal suppression of growth of microorganisms was noted in group with using 0.1% MB with laser radiation 3 minutes without centrifugation after 24 hours. Maximal suppression of growth was noted in group after centrifugation with 0.05% MB with exposure of laser 3 min. after 48 hours. Sensitivity of pathogenic culture of Candida albicans to application of B and laser raises accordingly to increase of concentration of MB.

Photodynamic effect of light-emitting diode light on cell growth inhibition induced by methylene blue

The aim of this study was to propose the use of red light-emitting diode (LED) as an alternative light source for methylene blue (MB) photosensitizing effect in photodynamic therapy (PDT). Its effectiveness was tested against Staphylococcus aureus (ATCC 26923), Escherichia coli (ATCC 26922), Candida albicans (ATCC 90028) and Artemia salina. The maximum absorption of the LED lamps was at a wavelength of 663 nm, at intensities of 2,4,6 and 12 J.cm-2 for 10, 20, 30 and 60 min of exposure, respectively. Assays with and without LED exposure were carried out in plates containing MB at concentrations of 7 to 140.8 (micro) M for microorganisms and 13.35 to 668.5 (micro) M for microorganisms or microcrustaceans. The LED exposure induced more than 93.05%, 93.7% and 93.33% of growth inhibition for concentrations of 42.2 (micro)M for S.aureus (D-value=12.05 min) and 35.2 (micro)M for E.coli (D-value=11.51 min) and C.albicans (D-value=12.18 min), respectively after 20 min of exposure. LED exposure for 1 h increased the cytotoxic effect of MB against A.salina from 27% to 75%. Red LED is a promising light device for PDT that can effectively inhibit bacteria, yeast and microcrustacean growth.

Study of germ tube formation by Candida albicans after photodynamic antimicrobial chemotherapy (PACT)

Due to the augmented number of immunocompromised patients, the infections associated to the pathogen of the genus Candida have increased dramatically in the recent years. In order to proliferate, Candida albicans can produce a germ tube formation extending from the cells. The germ tube formation is a transition state from budding to hyphal cells, and represents an essential stage for virulence. In this work we studied the effect of the photodynamic antimicrobial chemotherapy (PACT), a potential antimicrobial treatment on the germ tube formation by C. albicans. Germ tube formation was induced by goat serum after different treatments with Methylene blue (MB) and Laser (683nm). Our results demonstrated that photodynamic therapy using MB, as a photosensitizing drug; inhibits both the growth and the germ tube formation by C. albicans. Thus, our results suggest the possibility that Methylene blue, combined with light in a specific wavelength, can be used as a promising novel antifungal agent.

Photodynamic activity of water-soluble phthalocyanine zinc(II) complexes against pathogenic microorganisms

Photodynamic activity of tetrakis-(3-methylpyridyloxy)- and tetrakis-(4-sulfophenoxy)-phthalocyanine zinc(II) toward the gram-positive Staphylococcus aureus, the gram-negative Pseudomonas aeruginosa, and the fungi Candida albicans was studied. The drug uptake dependency with an inverse behavior to the cell density was observed. The cationic photosensitizer completely inactivated S. aureus and C. albicans, and with 4 log10 P. aeruginosa. The photoinactivation at mild experimental conditions, such as drug dose of 1.5 microM and fluence of 50 mW cm(-2) for 10 min irradiation time, was shown.

Candida albicans inactivation and cell membrane integrity damage by microwave irradiation

In indicating the microwave irradiation for disinfecting dentures it is necessary to see how this procedure influences Candida albicans integrity and viability. The aim of this study was to evaluate the ability of microwaves to inactivate C. albicans and damage cell membrane integrity. Two 200-ml C. albicans (ATCC 10231) suspensions were obtained. A sterile denture was placed in a beaker containing the Experimental (ES) or the Control suspension (CS). ES was microwaved at 650 W for 6 min. Suspensions were optically counted using methylene blue dye uptake as indicative of membrane-damaged cells; spread on Agar Sabouraud dextrose (ASD) for viability assay; or spectrophotometrically measured at 550 nm. Cell-free solutions were submitted to content analyses of protein (Bradford and Pyrogallol red methods); Ca++ (Cresolftaleine complexone method); DNA (spectrophotometer measurements at 260 nm) and K+ (selective electrode technique). Data were analysed by Student's t- or Wilcoxon z-tests (alpha = 0.05). All ES cells demonstrated cell membrane damage. Viable cells were non-existent in the ES ASD plates. No significant difference in optical density between ES and CS was observed (P=0.272). ES cells released significantly high protein (P<0.001, Bradford; P=0.005, Pyrogallol red), K+ (P<0.001), Ca++ (P=0.012) and DNA (P=0.046) contents. Microwaves inactivated C. albicans and damaged cell membrane integrity.

Phenotypic switching and its influence on expression of virulence factors by Candida albicans causing candidiasis in human immunodeficiency virus-infected patients

PURPOSE

The purpose of the present study was to determine the degree of expression of virulence factors such as adherence, cell surface hydrophobicity (CSH) and production of proteinase by different morphological forms of Candida albicans causing oral candidiasis in human immunodeficiency virus (HIV)-infected individuals.

METHODS

C. albicans 3153A and two strains isolated from oral thrush in HIV infected individuals were induced to undergo phenotypic switching by exposure to UV light and the degree of expression of virulence factors by the different morphological forms was studied.

RESULTS

Three different morphological forms of C. albicans were obtained namely, star (S), wrinkled (W) and ring (R) types from the original smooth (O) variety. It was found that proteinase production was greatest with the W type followed by the R type and O type. The S type produced the least proteinase. Expression of cell surface hydrophobicity and adherence was greatest in the O type followed by the R and then the W type and finally the S type.

CONCLUSIONS

The differential expression of virulence factors occurs with different phenotypic forms of C. albicans and this may provide a particular morphological type with a distinct advantage over other types in causing candidiasis.

Critical role of DNA checkpoints in mediating genotoxic-stress-induced filamentous growth in Candida albicans

The polymorphic fungus Candida albicans switches from yeast to filamentous growth in response to a range of genotoxic insults, including inhibition of DNA synthesis by hydroxyurea (HU) or aphidicolin (AC), depletion of the ribonucleotide-reductase subunit Rnr2p, and DNA damage induced by methylmethane sulfonate (MMS) or UV light (UV). Deleting RAD53, which encodes a downstream effector kinase for both the DNA-replication and DNA-damage checkpoint pathways, completely abolished the filamentous growth caused by all the genotoxins tested. Deleting RAD9, which encodes a signal transducer of the DNA-damage checkpoint, specifically blocked the filamentous growth induced by MMS or UV but not that induced by HU or AC. Deleting MRC1, the counterpart of RAD9 in the DNA-replication checkpoint, impaired DNA synthesis and caused cell elongation even in the absence of external genotoxic insults. Together, the results indicate that the DNA-replication/damage checkpoints are critically required for the induction of filamentous growth by genotoxic stress. In addition, either of two mutations in the FHA1 domain of Rad53p, G65A, and N104A, nearly completely blocked the filamentous-growth response but had no significant deleterious effect on cell-cycle arrest. These results suggest that the FHA domain, known for its ability to bind phosphopeptides, has an important role in mediating genotoxic-stress-induced filamentous growth and that such growth is a specific, Rad53p-regulated cellular response in C. albicans.

Pityriacitrin--a potent UV filter produced by Malassezia furfur and its effect on human skin microflora

In Malassezia furfur, tryptophan as the main nitrogen source induces production of the potent ultraviolet-absorbing indole compound pityriacitrin. An in vitro study about the effects of pityriacitrin on other human skin microorganisms is presented, with special focus on Candida albicans and staphylococci in which its toxicity and UV-protective capacity were investigated. Candida albicans was irradiated with UVB light either in the presence or in the absence of pityriacitrin (11 mmol) and the growth rate was determined. A UVB dose of 1 J cm(-2) caused death of the fungi without pityriacitrin, whereas those in the presence of pityriacitrin showed almost unaffected growth. A diffusion test in staphylococci revealed no antibiotic effects of pityriacitrin. For testing of an ultraviolet-protective effect, staphylococci were either inoculated and irradiated in a plate model for visual assessment of growth or inoculated and irradiated in square quartz cylinders for quantitative measurement of cell density, each time in the absence or presence of pityriacitrin. Cell density of the bacterial suspensions exhibited nearly no influence of pityriacitrin on growth rates, while again a UV-protective effect was observed. In summary, pityriacitrin has an ultraviolet-protective effect on Candida albicans and staphylococci with no toxicity in the range tested.

Effects of UV intensity and water turbidity on microbial indicator inactivation

The effects of UV intensity and turbidity on selected microbial indicator inactivation were investigated. Results showed that UV disinfection was effective in killing all the selected microbial indicators, the resistance order of the microorganisms was as follows: MS-2 coliphage > Bacillus subtilis > E. coli > Staphylococcus aureus and Candida albicans. UV intensity had influence on the inactivation of all the microorganisms, high UV disinfection efficency was obtained with higher UV intensity. Turbidity had impact on the bacteria inactivation rate, but there was no evidence that turbidity had any negative contribution to MS-2 coliphage. Under the same UV dosage, higher UV intensity could overcome the negative influence of turbidity on UV performance, enhanced microorganism inactivation effect in turbidity water.

Disinfection of Root Canals Using Er:YAG Laser at Different Frequencies

OBJECTIVE

This study evaluated, in vitro, the degree of disinfection of the Er:YAG laser in root canals contaminated with Bacillus subtilis, Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, and Candida albicans, for 28 days.

METHODS

Forty-six single-rooted human teeth were divided into five groups of eight teeth each; three teeth were used as negative controls and three as positive controls. After contamination, the root canals were prepared mechanically. Three groups were irradiated with Er:YAG laser at 100 mJ, varying the frequency (7, 10, and 16 Hz). Two groups were irrigated with 1.0% and 2.5% NaOCl solution. After treatment, two sterilized paper cones were placed in the root canals for 5 min. One cone was transferred to 2.0 mL of Letheen broth culture medium, incubated at 37 degrees C for 48 h, and then 0.1 mL of that solution was placed in 2.0 mL of brain heart infusion for 48 h to determine microbial growth. The other cone was transferred to a test pipette with peptone and water for serial dilution and spread in Müeller Hinton medium. After 24 h of incubation, the colony-forming units (CFUs) were counted.

RESULTS

There was a microbial reduction of 85.33% for the group irradiated with Er:YAG laser at 100 mJ/7 Hz, 74.58% at 100 mJ/10 Hz, and 89.50% at 100 mJ/16 Hz. For the groups irrigated with 1.0% and 2.5% NaOCl solution, 83.15% and 84.46% values of microbial reduction were obtained respectively.

CONCLUSION

All the groups showed statistically similar results (p > 0.05%). No method totally eliminated microorganisms.

Effectiveness of microwave irradiation on the disinfection of complete dentures

PURPOSE

The purpose of this study was to evaluate the effectiveness of microwave irradiation on the disinfection of simulated complete dentures.

MATERIALS AND METHODS

Eighty dentures were fabricated in a standardized procedure and subjected to ethylene oxide sterilization. The dentures were individually inoculated (10(7) cfu/mL) with tryptic soy broth (TSB) media containing one of the tested microorganisms (Candida albicans, Streptoccus aureus, Bacillus subtilis, and Pseudomonas aeruginosa). After 48 hours of incubation at 37 degrees C, 40 dentures were individually immersed in 200 mL of water and submitted to microwave irradiation at 650 W for 6 minutes. Forty nonirradiated dentures were used as positive controls. Replicate aliquots (25 microL) of suspensions were plated at dilutions of 10(-3) to 10(-6) on plates of selective media appropriate for each organism. All plates were incubated at 37 degrees C for 48 hours. TSB beakers with the microwaved dentures were incubated at 37 degrees C for 7 more days. After incubation, the number of colony-forming units was counted and the data were statistically analyzed by Kruskal-Wallis test (alpha = .05).

RESULTS

No evidence of growth was observed at 48 hours for S. aureus, B. subtilis, and C. albicans. Dentures contaminated with P. aeruginosa showed small growth on 2 plates. After 7 days incubation at 37 degrees C, no growth was visible in the TSB beakers of S. aureus and C. albicans. Turbidity was observed in 3 broth beakers, 2 from P. aeruginosa and 1 from B. subtilis.

CONCLUSION

Microwave irradiation for 6 minutes at 650 W produced sterilization of complete dentures contaminated with S. aureus and C. albicans and disinfection of those contaminated with P. aeruginosa and B. subtilis.

Photosensitization of different Candida species by low power laser light

The aim of this study was to evaluate the effects of the laser radiation (685 nm) associated with photosensitizers on viability of different species of Candida genus. Suspensions of Candida albicans, Candida dubliniensis, Candida krusei and Candida tropicalis, containing 10(6) viable cells per milliliter were obtained with the aid of a Neubauer's chamber. From each species, 10 samples of the cell suspension were irradiated with diode laser (685 nm) with 28 J/cm2 in the presence of methylene blue (0.1 mg/ml), 10 samples were only treated with methylene blue, 10 samples were irradiated with laser in the absence of the dye, 10 samples were treated with the dye and irradiated with laser light and 10 samples were exposed to neither the laser light nor to the methylene blue dye. From each sample, serial dilutions of 10(-2) and 10(-3) were obtained and aliquots of 0.1 ml of each dilution were plated in duplicate on Sabouraud dextrose agar. After incubation at 37 degrees C for 48 h, the number of colony-forming units (CFU/ml) was obtained and data were submitted to ANOVA and Tukey's test (p<0.05). Laser radiation in the presence of methylene blue reduced the number of CFU/ml in 88.6% for C. albicans, 84.8% for C. dubliniensis, 91.6% for C. krusei and 82.3% for C. tropicalis. Despite this, only laser radiation or methylene blue did not reduce significantly the number of CFU/ml of Candida samples, except for C. tropicalis. It could be concluded that the photo activation of methylene blue by the red laser radiation at 685 nm presented fungicide effect on all Candida species studied.

Effects of repeated low-dose UVB irradiation on the hyphal growth of Candida albicans

Ultraviolet B light (UVB) can have negative phototropic effects on fungi. Candida albicans is often found on human skin exposed to UVB. Therefore, it is of medical interest to know whether a negative phototropic response to UVB irradiation can support an invasive growth of this potentially dangerous agent. In our study we investigated how repeated irradiation with low doses of UVB can influence the hyphal growth of C. albicans. Six randomly chosen strains of C. albicans were tested. Formation of hyphae was induced and maintained within transparent agar plates. The fungi were exposed to UVB three times daily for 7 days from either the observe or the reverse side during incubation. The wavelength spectrum was in the range of 310-315 nm, single doses were between 0.0018 and 0.432 J cm(-2). After 7 days the morphology and growth direction of C. albicans cells were determined microscopically. All six strains showed a common and dose-dependent response to UVB irradiation: the progression of hyphal growth was inhibited, no phototropic effects were seen and as a new finding an increased formation of blastospores was observed. We conclude that an irradiation of human skin colonized by C. albicans with doses of UVB that can occur under natural or artificial conditions is unlikely to trigger skin invasion by C. albicans.

Sensitivity of Candida albicans germ tubes and biofilms to photofrin-mediated phototoxicity

Treatment of mucocutaneous and cutaneous Candida albicans infections with photosensitizing agents and light, termed photodynamic therapy (PDT), offers an alternative to conventional treatments. Initial studies using the clinically approved photosensitizer Photofrin demonstrated the susceptibility of C. albicans to its photodynamic effects. In the present study, we have further refined parameters for Photofrin-mediated photodynamic action against C. albicans and examined whether mechanisms commonly used by microorganisms to subvert either antimicrobial oxidative defenses or antimicrobial therapy, including biofilm formation, were operative. In buffer and defined medium, germ tubes preloaded with Photofrin retained their photosensitivity for up to 2 hours, indicating the absence of degradation or export of Photofrin by the organism. The addition of serum resulted in a gradual loss of photosensitivity over 2 hours. In contrast to an adaptive response by germ tubes to oxidative stress by hydrogen peroxide, there was no adaptive response to singlet oxygen-mediated stress by photodynamic action. C. albicans biofilms were sensitive to Photofrin-mediated phototoxicity in a dose-dependent manner. Finally, the metabolic activity of C. albicans biofilms following photodynamic insult was significantly lower than that of biofilms treated with amphotericin B for the same time period. These results demonstrate that several of the mechanisms microorganisms use to subvert either antimicrobial oxidative defenses or antimicrobial therapy are apparently not operative during Photofrin-mediated photodynamic treatment of C. albicans. These observations provide support and rationale for the continued investigation of PDT as an adjunctive, or possibly alternative, mode of therapy against cutaneous and mucocutaneous candidiasis.

Antifungal effects of a tissue conditioner coating agent with TiO2 photocatalyst

Tissue conditioners are susceptible to colonization by microorganisms. Therefore, the prevention of biofilm formation are important for oral hygiene. However, mechanical and chemical cleaning methods may cause clinical problems such as deformation or surface degradation of tissue conditioners. The objective of this study is to evaluate the antifungal effects of coating agents with a TiO2 photocatalyst. Photocatalytic antifungal effects on C. albicans biofilms and photodegradation effects of adsorbed protein were measured by colorimetric assays. Scanning electron microscopy was used to examine morphological changes in C. albicans. Viscosities of coating agents increased with incorporation of TiO2. However, both of coating agents with TiO2 were acceptable to the application by brush. The antifungal and protein degradation effects increased with the concentration of TiO2 in the coating agents. These effects also increased with radiation time. After 90 min radiation, the viability of C. albicans was reduced to 16.2+/-3.3 %. Scanning electron microscopy observation showed C. albicans remained on the coated surfaces even after 90 min radiation. These results suggest that coating agents with TiO2 photocatalyst can be effective for the maintenance of tissue conditioners when dentures are removed; during sleep.

Effect of low-level laser therapy on Candida albicans growth in patients with denture stomatitis

OBJECTIVE

The purpose of our report is to present the effect of low-level laser therapy on Candida albicans growth and palatal inflammation in two patients with denture stomatitis.

BACKGROUND DATA

The most common oral mucosal disorder in denture wearers is denture stomatitis, a condition that is usually associated with the presence of the yeast Candida albicans. Different treatment methods have been suggested to treat this symptom, none of which is proven to be absolutely effective.

METHODS

Two denture-wearing patients, both with palatal inflammation diagnosed as Newton type II denture stomatitis were treated with low-power semiconductor diode laser (BTL-2000, Prague, Czech Republic) at different wavelengths (685 and 830 nm) for 5 d consecutively. In both patients, palatal mucosa and acrylic denture base were irradiated in noncontact mode (probe distance of 0.5 cm from irradiated area) with different exposure times-5 min (830 nm, 3.0 J/cm2, 60 mW) and 10 min (685 nm, 3.0 J/cm2, 30 mW). The effect of laser light on fungal growth in vivo was evaluated after the final treatment using the swab method and semiquantitative estimation of Candida albicans colonies growth on agar plates. The severity of inflammation was evaluated using clinical criteria.

RESULTS

After lowlevel laser treatment, the reduction of yeast colonies on the agar plates was observed and palatal inflammation was diminished.

CONCLUSION

LLLT is effective in the treatment of denture stomatitis. Further placebo controlled studies are in progress.

Mechanistic study of the photodynamic inactivation of Candida albicans by a cationic porphyrin

The growing resistance against antifungal agents has renewed the search for alternative treatment modalities, and antimicrobial photodynamic inactivation (PDI) is a potential candidate. The cationic porphyrin 5-phenyl-10,15,20-Tris(N-methyl-4-pyridyl)porphyrin chloride (TriP[4]) is a photosensitizer that in combination with light can inactivate bacteria, fungi, and viruses. For future improvement of the efficacy of PDI of clinically relevant fungi such as Candida albicans, we sought to understand the working mechanism by following the response of C. albicans exposed to PDI using fluorescence confocal microscopy and freeze-fracture electron microscopy. The following events were observed under dark conditions: TriP[4] binds to the cell envelope of C. albicans, and none or very little TriP[4] enters the cell. Upon illumination the cell membrane is damaged and eventually becomes permeable for TriP[4]. After lethal membrane damage, a massive influx of TriP[4] into the cell occurs. Only the vacuole membrane is resistant to PDI-induced damage once TriP[4] passes the plasma membrane. Increasing the incubation time of C. albicans with TriP[4] prior to illumination did not increase the influx of TriP[4] into the cell or the efficacy of PDI. After the replacement of 100% phosphate-buffered saline (PBS) by 10% PBS as the medium, C. albicans became permeable for TriP[4] during dark incubation and the efficacy of PDI increased dramatically. In conclusion, C. albicans can be successfully inactivated by the cationic porphyrin TriP[4], and the cytoplasmic membrane is the target organelle. TriP[4] influx occurred only after cell death.

Bioadhesive patch-based delivery of 5-aminolevulinic acid to the nail for photodynamic therapy of onychomycosis

The in vitro penetration of 5-aminolevulinic acid (ALA) across human nail and into neonate porcine hoof when released from a novel bioadhesive patch containing 50 mg cm(-2) ALA is described. ALA is a naturally occurring precursor of the photosensitiser protoporphyrin IX (PpIX). Topical application of excess ALA bypasses negative feedback inhibition and yields photosensitising concentrations of PpIX at the application site. ALA-based photodynamic therapy (PDT) has been extensively investigated in the topical treatment of various skin neoplasias. Recently, its use has been extended to the microbiological field. If sufficient concentrations of ALA could be achieved within the nail matrix, and at the nail bed, PDT may prove to be a useful treatment for onychomycosis. Patch application for 24 h allowed an ALA concentration of 2.8 mM to be achieved on the ventral side of excised human nail. Application for 48 h induced a concentration of 6.9 mM. Application time had no significant effect on the ALA concentration at mean depths of 2.375 mm in neonate porcine, with application times of 24, 48 and 72 h all producing concentrations of 0.1 mM. Incubation of Candida albicans and Trichophyton interdigitale with ALA concentrations of 10.0 mM for 30 min and 6 h, respectively, caused reductions in viability of 87% and 42%, respectively, following irradiation with red light. Incubation with 0.1 mM ALA for 30 min and 6 h, respectively, caused reductions in viability of 32% for Candida albicans and 6% for Trichophyton interdigitale, following irradiation. Drug penetration across nail may be improved using penetration enhancers, or by filing of the impenetrable dorsal surface of the nail. Moreover, iron chelators can be used to increase PpIX production for a given ALA dose. Therefore, with suitable modifications, ALA-PDT may prove to be a viable alternative in the treatment of onychomycosis.

Effect of albumin on the photodynamic inactivation of microorganisms by a cationic porphyrin

BACKGROUND

Photodynamic inactivation (PDI) employs visible light and a photosensitizer to inactivate cells. The technique is currently clinically used for the treatment of several malignancies. However, the PDI of microorganisms still remains in the research phase.

PURPOSE

To study the effect of human blood plasma and human serum albumin (HSA) on the PDI of Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans.

METHODS

PDI experiments were performed using white light (30 mW cm-2) and the cationic 5-phenyl-10,15,20-tris(N-methyl-4-pyridyl)porphyrin chloride (TriP[4]) as photosensitizer.

RESULTS

The microorganisms could be successfully photoinactivated by TriP[4] when suspended in phosphate buffered saline (PBS). In this medium, P. aeruginosa was the most resistant microorganism. Changing the suspending medium from PBS to human blood plasma reduced the PDI of all three microorganisms. In human blood plasma C. albicans was the most resistant microorganism. The same results were obtained with 4.5% and 7% HSA/PBS suspensions.

CONCLUSIONS

Albumin inhibits the PDI of S. aureus, P. aeruginosa and C. albicans in a dose dependent manner. However, our results are encouraging towards the potential future application of PDI for the treatment of superficial wound infections caused by S. aureus, P. aeruginosa and C. albicans.

Evaluation Of The Antimicrobial Effect Of Er:YAG Laser Irradiation Versus 1% Sodium Hypochlorite Irrigation For Root Canal Disinfection

This laboratory study evaluated Er:YAG laser antibacterial action in infected root canals. Forty-eight maxillary central incisors were used. After canal preparation, the teeth were autoclaved and divided into four groups: (1) non-treated teeth (control group); (2) teeth treated with NaOCl; (3) teeth irradiated with Er:YAG laser (7 Hz, 100 mJ, 80 pulses/canal, 11 sec) to the working length; (4) teeth irradiated similarly to, but 3 mm short, of the apex. The root canals from Groups 2, 3 and 4 were inoculated with 4 bacteria: Bacillus subtillus, Enterococcus faecalis, Pseudomonas aeruginosa, and Staphylococcus aureus, together with Candida albicans, and maintained for 24 h at 37 degrees C. All suspensions were adjusted to tube 2 of the MacFarland scale. The intracanal material was then collected with sterile paper points, which were placed in the canals for 5 min and then immersed in 5 ml of BHI medium. This was then seeded onto agar and stained by Gram's method. The NaOCl solutions and the Er:YAG laser irradiation to working length were effective against all five micro-organisms; however, 70% of the specimens irradiated 3 mm short of the apex remained infected.

In vitro effect of 5-aminolaevulinic acid plus visible light on Candida albicans

Photodynamic therapy, currently used as an alternative technique for the treatment of superficial non-melanoma skin cancers, has been employed in vitro to kill different species of microorganisms. Here the development of Candida albicans colonies has been measured after application of 5-aminolaevulinic acid (ALA) plus visible light (VIS) irradiation. C. albicans suspensions (10 colony forming units microl(-1)) have been prepared. For the experiment 30 microl of suspension have been incubated in the dark for 3 h, with increasing concentrations of ALA (125, 250, 300, 350, 400, 450, 500, 550, 600, 750, 1000 mg ml(-1)) and then irradiated with a fixed dose (40 J cm(-2)) of VIS. Immediately after the irradiative session, the C. albicans suspensions were disseminated on dishes containing a Sabouraud agar + CAF medium and cultured in the dark at 27 degree C; after 48 h colony development has been measured. In the same way four controls have been prepared: (i)C. albicans suspensions not treated with ALA-PDT; (ii)C. albicans suspensions incubated with increasing ALA concentrations without VIS; (iii)C. albicans suspensions irradiated with 40 J cm(-2) of VIS without ALA; (iv)C. albicans suspensions irradiated immediately after the addition of increasing concentrations of ALA without the 3 h incubation. Colonies treated with ALA-PDT have been studied with electron microscopy (E.M.). It was found that: (i) none of the controls prepared modified the development of C. albicans colonies; (ii) ALA plus VIS inhibited C. albicans growth in a concentration-dependent way: up to 250 mg ml of ALA concentrations did not affect C. albicans cells, 300 mg ml(-1) induced a 50% reduction in the number of colonies, a complete inhibition started from concentrations of 600 mg ml(-1); (iii) after ALA-PDT E.M. showed modifications of the cell membranes. From the results it is concluded ALA plus VIS light is able to kill C. albicans colonies, at least in vitro. Although other pharmacological approaches are available, further studies could show that PDT is a potential treatment for candidosis.

Effectiveness of microwave sterilization on three hard chairside reline resins

PURPOSE

The aim of this study was to evaluate the effectiveness of microwave irradiation sterilization on hard chairside reline resins.

MATERIALS AND METHODS

Specimens of three reline resins (Kooliner, Tokuso Rebase, and Ufi Gel Hard) were fabricated and subjected to ethylene oxide sterilization. The specimens were then individually inoculated (10(7) cfu/mL) with Tryptic Soy Broth media containing one of the tested microorganisms (C albicans, S aureus, B subtilis, and P aeruginosa). After 48 hours at 37 degrees C, the samples were vortexed for 1 minute and allowed to stand for 9 minutes, followed by a short vortex to resuspend any organisms present. After inoculation, 40 specimens of each material were immersed in 200 mL of water and subjected to microwave irradiation at 650 W for 6 minutes. Forty non-irradiated specimens were used as positive controls. Replicate specimens (25 microL) of suspension were plated at dilutions of 10(-3) to 10(-6) on plates of selective media appropriate for each organism. All plates were incubated at 37 degrees C for 48 hours. After incubation, colonies were counted, and the data were statistically analyzed by the Kruskal-Wallis test. Twelve specimens of each material were prepared for SEM.

RESULTS

All immersed specimens showed consistent sterilization of all the individual organisms after microwave irradiation. SEM examination indicated an alteration in cell morphology after microwave irradiation.

CONCLUSION

Microwave sterilization for 6 minutes at 650 W proved to be effective for the sterilization of hard chairside reline resins.

Factors affecting the antibacterial effects of Nd:YAG laser in vivo

BACKGROUND AND OBJECTIVES

One of the main advantages of laser surgery is it's bactericidal effect which reduces the risk of postoperative infections. Several study designs have been set to investigate this effect. Aim of this study was to research if the bactericidal effect of laser tool was affected from several factors in vitro studies.

STUDY DESIGN/MATERIALS AND METHODS

To determinate and investigate the bactericidal effect of laser in an original model, alpha-hemolytic streptococcus, Bacterioides fragilis, Neisseria, Streptococcus salivarius, Staphylococcus aureus, and Candida albicans were prepared in 10(4), 10(6) and 10(8) inoculum and placed in Mueller-Hinton Broth which have five different proportions of sheep blood. Samples which exposed with various energy levels of Nd:YAG laser were spread on agar plates, and at the end of an incubation time the colonization counted comparatively. The lowest energy level without colonization was accepted as minimal bactericidal energy level.

RESULTS

Highest minimum bactericidal energy level is used for alpha-hemolytic streptococcus and lowest values for neisseria. Bactericidal effect decreased on suspensions, of which population of microorganisms are high and hemoglobin concentration was high in the broth.

CONCLUSIONS

These findings suggest that the Nd:YAG laser has a higher bactericidal effect when sheep blood is added to the media. Factors like population and type of bacteria in the irradiated suspension affect minimum bactericidal energy level.

The photobleaching of disulfonated aluminium phthalocyanine in microbial systems

Front-face illumination spectroscopic techniques were used to study photobleaching of disulfonated aluminium phthalocyanine (AlPcS2) in the bacteria and yeast cells Escherichia coil, Porphyromonas gingivalis (Gram-negative bacteria), Streptococcus mutans (a Gram-positive bacterium), and the yeast Candida albicans. The photobleaching of AlPcS2 with the microbes studied is complex, involving reactive species generated by type I and type II processes with the rate dependent on the relative contributions of the different photobleaching mechanisms. The average rate of photobleaching of the AlPcS2 monomer in the presence of both E. coli and C. albicans increases as the fluence of the illumination source decreases. The effects of oxygen and sensitiser concentration on the rate of AlPcS2 photobleaching in these systems are also investigated.

Ultraviolet disinfection with a novel microwave-powered device

AIMS

To evaluate the antimicrobial efficacy of a novel u.v. beaker, powered in a domestic microwave oven.

METHODS AND RESULTS

Three beakers were compared, with most rapid killing obtained in the Neutra Plasma 50. Ultraviolet light generated within the beakers efficiently killed planktonic and surface-associated Streptococcus mutans, Pseudomonas aeruginosa, vegetative Bacillus stearothermophilus, herpes simplex and polio viruses. Candida albicans and Mycobacterium phleii were less rapidly killed, and only 70% inactivation of B. stearothermophilus endospores was achieved. Irradiation for 45 s reduced viable bacterial counts in saliva by > 99%.

CONCLUSIONS

The u.v.-generating beakers efficiently reduced viable counts of bacteria, yeast and viruses. Kinetics of killing varied, reflecting the fact that lethal mechanisms are complex, and probably depend on interplay between u.v. and heat.

SIGNIFICANCE AND IMPACT OF THE STUDY

This novel method of generating u.v., using a cheap and widely available power source, provides a rapid, inexpensive and non-toxic method of disinfection with a wide range of applications in hospitals, clinics and the home.

How to improve instrument disinfection by ultrasound

Ultrasound technologies have a wide range of hospital and dental applications which include cleaning and disinfection of surgical and dental instruments. We measured the germicidal efficacy of sonication, with or without chemical disinfectants, in an ultrasonic bath delivering a frequency of 35 kHz and an intensity of 0.66 W/cm2. Cultures of Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans were exposed to ultrasound and to an amine-based disinfectant in non-bactericidal concentrations. Ultrasonication for 60 min alone did not cause a significant killing of the bacteria and yeast. However, we were able to show that sonication can act as a powerful synergistic agent to increase the cidal efficacy of the disinfectant against S. aureus and P. aeruginosa. C. albicans was more resistant to the combination of ultrasound and chemical disinfection. The key role in the action of ultrasound in cleaning of instruments and perhaps in enhanced disinfection is played by cavitation phenomena. The distribution of cavitations in an ultrasonic bath is not homogenous. We found a similar synergistic effect of ultrasound and disinfectant in positions with low cavitation. The synergistic effect was not reduced inside rubber tubes. Before ultrasound can be accepted as an integral part of the cleaning and disinfection process of medical instruments, the influence of intensity and frequency of sonication and the effects of cavitation must be clarified.

Increase of Candida cell virulence by anticancer drugs and irradiation

The influence of anticancer drugs and irradiation on Candida cell proliferation, adherence to HeLa cells and susceptibility to antifungal drugs (amphotericin B and miconazole) and neutrophils were examined using two Candida albicans strains. After treatment with 5-fluorouracil (25 microg/ml to 250 microg/ml), cis-diammine-dichloroplatinum (10 microg/ml to 100 microg/ml), peplomycin (0.5 microg/ml to 5 microg/ml) or 137Cs (20 Gy to 40 Gy) for 3 days or more, surviving Candida cells proliferated more rapidly than did untreated control cells. Anticancer agent-pretreated Candida cells revealed an increased adhesion to HeLa cells corresponding to an increase of binding to the lectins. The concentration of half limited colony formation (IC50) of amphotericin B and miconazole was increased to near two-fold that of the control by pretreatment of Candida cells with the anticancer agents, except peplomycin, which only weakly increased IC50. In addition, the enolase and Candida acid proteinase activities in the culture supernatants were increased by pretreatment with the drugs and irradiation. Correspondingly, surviving Candida cells after these treatments were resistant to neutrophils, with a reduction to half of the killing. These results indicate that anti-cancer drugs and irradiation potentiate the virulence of Candida cells, or they eliminate Candida cells with low virulence, thereby enhancing the risk of oral and systemic candidiasis.

Killing of cutaneous microbial species by photodynamic therapy

BACKGROUND

Photodynamic therapy (PDT) utilizes photosensitizers and light. Whereas PDT use in cancer treatment has been widely accepted, antimicrobial PDT (APDT) is still in its early stages of development.

OBJECTIVES

To study microbial killing in vitro using APDT.

METHODS

We used a combination of methylene blue and visible light, and a range of microbial species representative of those encountered on the skin in health and disease. Using standard light intensity conditions (slide projector, 25 cm distance from target, 42 mW cm(-2)) and methylene blue dye at 100 microg mL(-1), kill rates and subsequent D-values were determined against Staphylococcus aureus, S. epidermidis, Streptococcus pyogenes, Corynebacterium minutissimum, Propionibacterium acnes and Candida albicans.

RESULTS

D-values for these species were 72, 66, 48, 120, 30 and 660 s, respectively. The effects of light intensity on the killing of S. epidermidis showed the kill rate to be proportional to the light intensity. A high rate of cell kill was also obtained using natural sunlight.

CONCLUSIONS

Overall, these results indicate that APDT of the skin may represent a useful alternative to conventional antimicrobial treatment.