Treatment of oral candidiasis with methylene blue-mediated photodynamic therapy in an immunodeficient murine model

Treatment of oral fungal infections using antimicrobial photodynamic therapy: a systematic review of currently available evidence

The aim was to review the efficacy of antimicrobial photodynamic therapy (PDT) in the treatment of oral fungal infections. To address the focused question "Should PDT be considered a possible treatment regimen for oral fungal infections?" PubMed/Medline and Google-Scholar databases were searched from 1997 up to March 2014 using various combinations of the following key words: "Candida albicans"; "Candidiasis"; "Candidosis"; "denture stomatitis"; "oral" and "photodynamic therapy". Original studies, experimental studies and articles published solely in English language were sought. Letters to the editor, historic reviews and unpublished data were excluded. Pattern of the present literature review was customized to mainly summarize the pertinent information. Fifteen studies (3 clinical and 12 experimental) were included. All studies reported antimicrobial PDT to be an effective antifungal treatment strategy. One study reported PDT and azole therapy to be equally effective in the treatment of oral fungal infections. Methylene blue, toluidine blue and porphyrin derivative were the most commonly used photosensitizers. The laser wavelengths and power output ranged between ∼455 nm-660 nm and 30 mW-400 mW. The energy fluence ranged between 26-245 J cm(-2) and the duration or irradiation ranged between 10 seconds and 26 minutes. Clinical effectiveness of antimicrobial PDT as a potent therapeutic strategy for oral fungal infections requires further investigations.

Antimicrobial photodynamic therapy: an effective alternative approach to control fungal infections

Skin mycoses are caused mainly by dermatophytes, which are fungal species that primarily infect areas rich in keratin such as hair, nails, and skin. Significantly, there are increasing rates of antimicrobial resistance among dermatophytes, especially for Trichophyton rubrum, the most frequent etiologic agent worldwide. Hence, investigators have been developing new therapeutic approaches, including photodynamic treatment. Photodynamic therapy (PDT) utilizes a photosensitive substance activated by a light source of a specific wavelength. The photoactivation induces cascades of photochemicals and photobiological events that cause irreversible changes in the exposed cells. Although photodynamic approaches are well established experimentally for the treatment of certain cutaneous infections, there is limited information about its mechanism of action for specific pathogens as well as the risks to healthy tissues. In this work, we have conducted a comprehensive review of the current knowledge of PDT as it specifically applies to fungal diseases. The data to date suggests that photodynamic treatment approaches hold great promise for combating certain fungal pathogens, particularly dermatophytes.

Clinical, biochemical and histological study of the effect of antimicrobial photodynamic therapy on oral mucositis induced by 5-fluorouracil in hamsters

Oral mucositis (OM) is a debilitating side effect of chemotherapy, which can be relieved by phototherapy. Antimicrobial photodynamic therapy (aPDT) may be used for the treatment of OM, when infection is present. However, there are no studies showing that aPDT affects tissue repair process when used in the treatment of lesions caused by OM. This work aims to evaluate the effect of aPDT in healing OM induced by 5-Fluorouracil (5-FU). Two hundred forty-five hamsters were divided into two groups, control (C) and experimental, which were subdivided into 4 subgroups (Ch, ChP, ChL, aPDT). C group received only the vehicle of chemotherapy and anesthesia, whereas all animals of the experimental groups received anesthesia and chemotherapy agent 5-FU to induce OM. Ch group received no OM treatment; ChP group received an application of methylene blue (MB) 0.01%; ChL received irradiation with low-power-laser (LPL-660 nm/120 J /cm(2)/40 mW/4.4 J per point); and aPDT received MB and LPL irradiation. OM Clinical severity were daily assessed by a blinded examiner. The animals were sacrificed after 5, 7 and 10 days of experiment and their oral mucosa were removed for biochemical (enzymatic activity of SOD and catalase) and histological analyzes (light microscopy). After statistical analysis was performed, results showed that aPDT reduced the severity of OM on the tenth day of the experiment, when compared to the initial OM score (p < 0.05), as well as increased keratinization with organized collagen deposition in the lamina propria. In conclusion, aPDT can be safely used in animals with infected OM because it does not affect lesion-repairing processes.

In vivo evaluation of photodynamic inactivation using Photodithazine® against Candida albicans

The use of animal models for PDI evaluation is an important step to prove the in vivo effectiveness of a treatment and may provide outcomes that are close to clinical situations, in comparison with in vitro studies.

Novel strategies to fight Candida species infection

In recent years, there has been a significant increase in the incidence of human fungal infections. The increase in cases of infection caused by Candida species, and the consequent excessive use of antimicrobials, has favored the emergence of resistance to conventional antifungal agents over the past decades. Consequently, Candida infections morbidity and mortality are also increasing. Therefore, new approaches are needed to improve the outcome of patients suffering from Candida infections, because it seems unlikely that the established standard treatments will drastically lower the morbidity of mucocutaneous Candida infections and the high mortality associated with invasive candidiasis. This review aims to present the last advances in the traditional antifungal therapy, and present an overview of novel strategies that are being explored for the treatment of Candida infections, with a special focus on combined antifungal agents, antifungal therapies with alternative compounds (plant extracts and essential oils), adjuvant immunotherapy, photodynamic therapy and laser therapy.

In vitro combination therapy using low dose clotrimazole and photodynamic therapy leads to enhanced killing of the dermatophyte Trichophyton rubrum

Background

Superficial infections of the skin and mucous membranes caused by dermatophyte fungi are amongst the most common and challenging infections to treat. Previously we demonstrated the phototoxic effects of photodynamic therapy (PDT) towards Trichophyton rubrum, using a green laser to photoactivate Rose Bengal (RB). The aim of this study was to evaluate whether we could; (1) achieve a similar effect using an inexpensive light-emitting diode (LED) to photoactivate RB and (2) to evaluate whether our PDT regime could be combined with standard antifungal drug therapy and increase its effectiveness.

Methods

We designed and built our own inexpensive green (530 nm) LED source and tested its efficacy as part our RB-PDT regime in vitro against T. rubrum. We also examined the potential benefits of incorporating PDT as part of combination therapy and whether the order in which this was done had an impact. First we subjected spore suspensions to sub-inhibitory concentrations of a number of antifungal agents (CLT, MCZ and TRB) for 72 hours followed by RB-PDT. Secondly we subjected spore suspensions to sub-inhibitory PDT followed by drug treatment and evaluated if there were any changes to the minimum inhibitory concentrations (MICs) of the drugs tested.

Results

The optimal conditions for photoinactivation of T. rubrum using RB-PDT alone were 140 μM of RB and 24 J/cm² of LED (equating to a 30-minute exposure). These parameters also caused a 100% reduction in the viability of the pathogenic yeast Candida albicans and the model fungus Saccharomyces cerevisiae. By combining our RB-PDT regime as an adjunct to antifungal drugs we were able to dramatically reduce the exposure times. Treatment of spore suspensions using a sub-inhibitory dose of clotrimazole (CLT) followed by RB-PDT, this order was critical, significantly reduced the exposure times required to achieve 100% inhibition of T. rubrum to 15 minutes as compared to RB-PDT alone.

Conclusions

The combination of antifungal drug and RB-PDT represents an attractive alternative to the current antifungal therapies used to treat superficial fungal diseases. Our approach has the potential to reduce treatment times and drug dosages which can also reduce drug toxicity and improve patient compliance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-014-0261-z) contains supplementary material, which is available to authorized users.

Photodynamic therapy has antifungal effect and reduces inflammatory signals in Candida albicans-induced murine vaginitis

BACKGROUND

Vaginal candidiasis (VC) is a disease that affects thousands of women of childbearing age, mainly caused by Candida albicans fungus. Photodynamic therapy (PDT) uses photosensitizing substances that are nontoxic in the dark, but able to produce reactive oxygen species when they are subjected to a light source. In this work our purpose was to investigate PDT effects on fungal burden and inflammatory cells in a murine model of C. albicans-induced vaginal candidiasis.

METHODS

Female BALB/c mice 6-10 weeks were estrogenized and maintained in this state during all experiment. After 72h, mices were inoculated intravaginally (IV) with 20μL of 2×10(5)C. albicans cells suspension. Mice were separated into 5 groups after five days: H (healthy), PBS (control), laser, MB (methylene blue) and PDT. PDT and MB groups received IV 20μL solution with 1mM of MB, others received PBS. PDT and laser groups were irradiated with a red laser (100mW, 660nm) in one (36J, 6min) or two sessions (18J, 3min). After the end of treatment, mice were submitted to microbiological and histomorphometric analysis with ImageJ software. Data were plotted by mean values and standard deviations of CFU/mL and percentage of inflammatory cells area. ANOVA and Bonferroni post-test were used and data were considered significant when p<0.05.

RESULTS

PDT significantly reduced C. albicans after the two tested protocols, however, percentage area of inflammatory cells was significantly reduced just with two sessions of PDT.

CONCLUSIONS

PDT with MB and red laser is a promising therapy for VC. It is able to reduce fungal infection in biofilm and inflammatory signals associated with VC in a murine model of vaginitis.

Photosensitization of in vitro biofilms formed on denture base resin

STATEMENT OF PROBLEM

Proper sterilization or disinfection of removable prostheses and surgical guides has been problematic in dental practice because of the absence of simple and low-cost techniques that do not cause damage to acrylic resins.

PURPOSE

The purpose of this study was to study the effect of photodynamic therapy against Streptococcus mutans, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans biofilms formed on acrylic resin specimens.

MATERIAL AND METHODS

The specimens were sterilized in ethylene oxide gas and submitted to in vitro biofilm growth. The photodynamic therapy consisted of the application of 0.05% methylene blue (P+) conjugated to irradiation with a light-emitting-diode of 630 nm and 150 mW (L+). The specimens were randomly divided into groups (n=5): negative control (P-L-); stained and irradiated at 10 J/cm(2) (P+L+ 10); stained and irradiated at 30 J/cm(2) (P+L+ 30); stained and not irradiated (P+L-); not stained and irradiated at 10 J/cm(2) (P-L+ 10); not stained and irradiated at 30 J/cm(2) (P-L+ 30); and gold standard (GS), sterilized. Afterward, the specimens were submitted to contact with culture medium agar for 10 minutes in petri plates, which were incubated for 48 hours at 37°C. The number of colony-forming units was obtained, and the data were expressed according to scores (1=0; 2=1-10; 3=11-100; 4=101-1000) and analyzed by the Friedman and Dunn tests (α=.05).

RESULTS

Streptococcus mutans was sensitized by (P+L-); P aeruginosa and C albicans were also sensitized by the dye but showed a slight microbial reduction with (P+L+ 30), as did S aureus (P>.05); E coli presented an initial score of 3 and achieved a bacterial reduction to score 2 with (P+L+ 30) (P=.039).

CONCLUSIONS

Photodynamic therapy was effective in reducing E coli counts on biofilms formed on acrylic resin specimens. The inhibition of microorganism growth tended to be directly proportional to the amount of energy provided by the light-emitting diode.

The potential of photodynamic therapy to treat esophageal candidiasis coexisting with esophageal cancer

BACKGROUND

Photodynamic therapy (PDT) has been used in recent years to deal with fungal infections because of the prevalence of fungi resistance to drugs. However, PDT for gastrointestinal fungal infection has not been reported. This study was conducted to assess the potential of PDT to deal with esophageal candidiasis.

METHODS

Two male patients with histological evidence of esophageal candidiasis coexisting with esophageal cancer were included in this retrospective study. Both patients were treated with PDT. This treatment was repeated at least 1month after the initial PDT if the patient still had residual cancer or esophageal candidiasis. Short-term efficacy was evaluated on the basis of endoscopy and histology findings. Further follow-up data were obtained from endoscopy results or telephone conversation.

RESULTS

The esophageal candidiasis located 21-24cm and 25-28cm from the incisors of case 1 reached complete remission after one and two PDT sessions, respectively. The esophageal cancer coexisting with esophageal candidiasis located 21-24cm from the incisors reached complete remission after two PDT sessions. No recurrence was found at a 14-month follow-up. The esophageal cancer located 30-35cm from the incisors reached partial response after three PDT sessions. Both of the esophageal candidiasis and the coexisting esophageal cancer at 23-26cm from the incisors of case 2 reached complete remission and the esophageal cancer at 34-37cm from the incisors reached complete remission after one PDT session. No recurrence was found at a 24-month follow-up. There were no serious adverse events found in either of the two cases.

CONCLUSION

Results of this preliminary study indicate that PDT may be a potential method to deal with esophageal candidiasis.

Fluconazole assists berberine to kill fluconazole-resistant Candida albicans

It was found in our previous study that berberine (BBR) and fluconazole (FLC) used concomitantly exhibited a synergism against FLC-resistant Candida albicans in vitro. The aim of the present study was to clarify how BBR and FLC worked synergistically and the underlying mechanism. Antifungal time-kill curves indicated that the synergistic effect of the two drugs was BBR dose dependent rather than FLC dose dependent. In addition, we found that BBR accumulated in C. albicans cells, especially in the nucleus, and resulted in cell cycle arrest and significant change in the transcription of cell cycle-related genes. Besides BBR, other DNA intercalators, including methylene blue, sanguinarine, and acridine orange, were all found to synergize with FLC against FLC-resistant C. albicans. Detection of intracellular BBR accumulation by fluorescence measurement showed that FLC played a role in increasing intracellular BBR concentration, probably due to its effect in disrupting the fungal cell membrane. Similar to the case with FLC, other antifungal agents acting on the cell membrane were able to synergize with BBR. Interestingly, we found that the efflux of intracellular BBR was FLC independent but strongly glucose dependent and associated with the drug efflux pump Cdr2p. These results suggest that BBR plays a major antifungal role in the synergism of FLC and BBR, while FLC plays a role in increasing the intracellular BBR concentration.

Light based anti-infectives: ultraviolet C irradiation, photodynamic therapy, blue light, and beyond

Owing to the worldwide increase in antibiotic resistance, researchers are investigating alternative anti-infective strategies to which it is supposed microorganisms will be unable to develop resistance. Prominent among these strategies, is a group of approaches which rely on light to deliver the killing blow. As is well known, ultraviolet light, particularly UVC (200-280 nm), is germicidal, but it has not been much developed as an anti-infective approach until recently, when it was realized that the possible adverse effects to host tissue were relatively minor compared to its high activity in killing pathogens. Photodynamic therapy is the combination of non-toxic photosensitizing dyes with harmless visible light that together produce abundant destructive reactive oxygen species (ROS). Certain cationic dyes or photosensitizers have good specificity for binding to microbial cells while sparing host mammalian cells and can be used for treating many localized infections, both superficial and even deep-seated by using fiber optic delivered light. Many microbial cells are highly sensitive to killing by blue light (400-470 nm) due to accumulation of naturally occurring photosensitizers such as porphyrins and flavins. Near infrared light has also been shown to have antimicrobial effects against certain species. Clinical applications of these technologies include skin, dental, wound, stomach, nasal, toenail and other infections which are amenable to effective light delivery.

Photodynamic fungicidal efficacy of hypericin and dimethyl methylene blue against azole-resistant Candida albicans strains

Antimicrobial photodynamic therapy (aPDT) is an emerging alternative to treat infections based on the use of photosensitisers (PSs) and visible light. To investigate the fungicidal effect of PDT against azole-resistant Candida albicans strains using two PSs with a different mechanism of action, hypericin (HYP) and 1,9-dimethyl methylene blue (DMMB), comparing their efficacy and the reactive oxygen species (ROS) species involved in their cytotoxicity. Azole-resistant and the azole-susceptible C. albicans strains were used. Solutions of 0.5 and 4 McFarland inoculum of each Candida strain were treated with different concentrations of each PS, and exposed to two light-emitting diode light fluences (18 and 37 J cm⁻²). Mechanistic insight was gained using several ROS quenchers. The minimal fungicidal concentration of HYP for ≥3 log₁₀ CFU reduction (0.5 McFarland) was 0.62 μmol l⁻¹ for most strains, whereas for DMMB it ranged between 1.25 and 2.5 μmol l⁻¹. Increasing the fluence to 37 J cm⁻² allowed to reduce the DMMB concentration. Higher concentrations of both PSs were required to reach a 6 log₁₀ reduction (4 McFarland). H₂O₂ was the main phototoxic species involved in the fungicidal effect of HYP-aPDT whereas ¹O₂ was more important for DMMB-based treatments. aPDT with either HYP or DMMB is effective in killing of C. albicans strains independent of their azole resistance pattern. HYP was more efficient at low fungal concentration and DMMB at higher concentrations.

Recent mouse and rat methods for the study of experimental oral candidiasis

The Candida genus expresses virulence factors that, when combined with immunosuppression and other risk factors, can cause different manifestations of oral candidiasis. The treatment of mucosal infections caused by Candida and the elucidation of the disease process have proven challenging. Therefore, the study of experimentally induced oral candidiasis in rats and mice is useful to clarify the etiopathology of this condition, improve diagnosis, and search for new therapeutic options because the disease process in these animals is similar to that of human candidiasis lesions. Here, we describe and discuss new studies involving rat and mouse models of oral candidiasis with respect to methods for inducing experimental infection, methods for evaluating the development of experimental candidiasis, and new treatment strategies for oral candidiasis.

Photodynamic potential of curcumin and blue LED against Streptococcus mutans in a planktonic culture

BACKGROUND

The photodynamic therapy (PDT) involves the use of light of specific wavelength to activate a nontoxic photosensitizing agent or dye in the presence of oxygen for eradication of target cells. In dentistry, this therapy is used to suppress the growth of microorganisms involved directly with dental decay and periodontitis process. There are evidences that curcumin dye is able to control microbial activity when illuminated with specific wavelength. The purpose of this study was to evaluate the in vitro efficacy of PDT using curcumin dye (Cur-C) in combination with a blue LED (L) device on a planktonic model of Streptococcus mutans (S. mutans).

METHODS

Suspensions (0.5 mL) containing S. mutans at 1×10(7)CFU mL(-1) were prepared and divided into 4 groups: Group C-L- (control: no treatment and 1 experimental condition), Group C+L- (curcumin at 3 different concentrations: 2000; 4000 and 8000 μM and 3 experimental conditions), Group C-L+ (LED at 3 different dosages: 24, 48 and 72 Jcm(-2) and 3 experimental conditions), and Group C+L+ (PDT group: curcumin at respective concentrations combined to LED dosages and 9 experimental conditions). Samples of each experimental condition were cultured in Petri dishes of BHI agar. Incubation in micro-aerophilia at 37°C for 48 h was performed for subsequent visual counting of CFU/mL. Data were transformed into log10 and analyzed by two-way ANOVA and Tukey's test at p<0.05.

RESULTS

Group C+L+, in specific experimental conditions, demonstrated a log bacterial reduction 70% higher than Group C-L-. Both groups C-L+ and C+L- presented a slight decrease in log bacterial counting.

CONCLUSION

This in vitro method was able to reduce the number of S. mutans in a planktonic suspension.

Imidazoacridinone derivatives as efficient sensitizers in photoantimicrobial chemotherapy

The objective of this study was to investigate a new potential photosensitizer (PS) in the photodynamic inactivation (PDI) of microorganisms in vitro (11 reference strains and 13 clinical isolates, representing common Gram-positive and Gram-negative human pathogens), with special emphasis on Candida albicans. We studied the light-induced cytotoxicity of the imidazoacridinone derivative C1330 toward fungal cells grown in planktonic form. We examined the influence of various parameters (time of incubation, PDI quencher effect, and C1330 accumulation in C. albicans cells) on the efficacy of light-dependent cytotoxicity. Additionally, we checked for the potential cyto- and phototoxic activity of C1330 against human dermal keratinocytes. In our research, we used a broadband incoherent blue light source (380 to 470 nm) with an output power of 100 mW/cm(2). In vitro studies showed that the C1330 action against C. albicans was a light-dependent process. C1330 was an efficient photosensitizer in the photodynamic inactivation of C. albicans, which reduced the growth of planktonic cells by 6.1 log10 units. Efficient accumulation of PS in the nucleus and vacuoles was observed after 30 min of incubation, which correlated with the highest photokilling efficacy. Significant changes in intracellular structure were observed upon illumination of C1330-incubated C. albicans cells. In the case of the human HaCaT cell line, approximately 40% of cells survived the treatment, which indicates the potential benefit of further study of the application of C1330 in photoantimicrobial chemotherapy. These data suggest that PDI may be a viable approach for the treatment of localized C. albicans infections.

Shining light on materials--a self-sterilising revolution

This review focuses on the development of light activated antimicrobial surfaces. These surfaces kill microbes by the action of light and have potential applications in domestic and healthcare settings. The inspiration for the new self-cleaning surfaces originates from photodynamic therapy where light is used to locate and destroy tumours. The first generation photosensitiser molecules, based on a porphyrin ring structure, could be considered as bioinspired and chemically related to chlorophyll. The review looks at developments of both soft polymeric surfaces with either surface bound or impregnated photosensitiser molecules; and hard inorganic surfaces such as modified titanium dioxide. The bacterial kill mechanisms are looked into with both surface types showing primary microbial kill through a radical induced pathway. The hard inorganic surfaces also show low bacterial adherence by means of a light activated photo-wetting of the surfaces meaning that they are "Easy Clean" and wash off microbes uniformly.

Photodynamic therapy induces an immune response against a bacterial pathogen

Photodynamic therapy (PDT) employs the triple combination of photosensitizers, visible light and ambient oxygen. When PDT is used for cancer, it has been observed that both arms of the host immune system (innate and adaptive) are activated. When PDT is used for infectious disease, however, it has been assumed that the direct antimicrobial PDT effect dominates. Murine arthritis caused by methicillin-resistant Staphylococcus aureus in the knee failed to respond to PDT with intravenously injected Photofrin(®). PDT with intra-articular Photofrin produced a biphasic dose response that killed bacteria without destroying host neutrophils. Methylene blue was the optimum photosensitizer to kill bacteria while preserving neutrophils. We used bioluminescence imaging to noninvasively monitor murine bacterial arthritis and found that PDT with intra-articular methylene blue was not only effective, but when used before infection, could protect the mice against a subsequent bacterial challenge. The data emphasize the importance of considering the host immune response in PDT for infectious disease.

In vitro photodynamic inactivation of Candida species and mouse fibroblasts with phenothiazinium photosensitisers and red light

In the present study, the in vitro susceptibilities of five Candida spp. to photodynamic antimicrobial chemotherapy (PACT) with four phenothiazinium derivatives, methylene blue (MB), new methylene blue N (NMBN), toluidine blue O (TBO) and the novel pentacyclic phenothiazinium photosensitiser S137, in combination with red light were investigated. The efficacy of each PS was determined, initially, based on its minimal inhibitory concentration (MIC). Additionally, we evaluated the effect of the photodynamic treatment with NMBN and S137 on Candida survival and on the mouse fibroblast cell line L929. MICs varied both among PS and species and decreased with light dose increase. For most treatments (species and fluences) NMBN and S137 showed the lowest MICs. MICs for NMBN and S137 were <2.5 μM for all the Candida species when a fluence of 25 J cm⁻² was used. PACT with NMBN (fluence of 15 J cm⁻²) resulted in reductions in survival from 0.3 log (Candida krusei) to 3 logs (C. parapsilosis). PACT with S137 was more effective than with NMBN. Fluence of 15 J cm⁻² resulted in reductions in survival from 1 log (C. krusei) to 3 logs (C. parapsilosis) and fluence of 25 J cm⁻² resulted in a reduction of approximately 2 logs (C. krusei) and between 3 and 4 logs in survival of the other 4 species of Candida. In vitro relative toxicities of the phenothiazinium PS to mammalian cells exhibited a similar trend to the antifungal data, i.e. greater toxicity and phototoxicity with NMBN and S137 compared to the established PS.

Curcumin-mediated photodynamic inactivation of Candida albicans in a murine model of oral candidiasis

In vitro investigations of curcumin-mediated photodynamic therapy (PDT) are encouraging, but there is a lack of reliable in vivo evidence of its efficacy. This study describes the photoinactivation of Candida albicans in a murine model of oral candidiasis, using curcumin as a photosensitizer. Forty immunosuppressed mice were orally inoculated with C. albicans and after five days, they received topical curcumin (20, 40 and 80 μM) and illumination with LED light. The use of curcumin or light alone were also investigated. Positive control animals did not receive any treatment and negative control animals were not inoculated with C. albicans. The number of surviving yeast cells was determined and analyzed by ANOVA and Tukey's post-hoc test (α = 0.05). Histological evaluation of the presence of yeast and inflammatory reaction was also conducted. All exposures to curcumin with LED light caused a significant reduction in C. albicans viability after PDT, but the use of 80 μM curcumin associated with light was able to induce the highest log10 reduction in colony counts (4 logs). It was concluded that curcumin-mediated PDT proved to be effective for in vivo inactivation of C. albicans without harming the host tissue of mice.

Effect of erythrosine- and LED-mediated photodynamic therapy on buccal candidiasis infection of immunosuppressed mice and Candida albicans adherence to buccal epithelial cells

OBJECTIVE

This study evaluated the effects of photodynamic therapy (PDT) on buccal candidiasis in mice and on the adherence of yeast to buccal epithelial cells (BECs) in vitro.

STUDY DESIGN

A total of 56 immunosuppressed mice with buccal candidiasis were subjected to PDT, consisting of treatment with erythrosine (400 μmol/L) followed by exposure to a green LED (14.34 J cm(-2)). After treatment, the yeasts recovered from the mice were quantified (CFU/mL) and analyzed for the effects of PDT on their adherence to BECs. The data were analyzed using ANOVA, the Tukey test, Kruskal-Wallis test and Student t test.

RESULTS

PDT significantly reduced the amount of yeast present in the lesions by 0.73 log(10) (P = .018) and reduced C. albicans adherence to BECs by 35% without damaging adjacent tissues (P = .045).

CONCLUSIONS

Photodynamic therapy exhibited antifungal effects against C. albicans biofilms formed in vivo and reduced the capacity of C. albicans to adhere to BECs in vitro.

Concepts and principles of photodynamic therapy as an alternative antifungal discovery platform

Opportunistic fungal pathogens may cause superficial or serious invasive infections, especially in immunocompromised and debilitated patients. Invasive mycoses represent an exponentially growing threat for human health due to a combination of slow diagnosis and the existence of relatively few classes of available and effective antifungal drugs. Therefore systemic fungal infections result in high attributable mortality. There is an urgent need to pursue and deploy novel and effective alternative antifungal countermeasures. Photodynamic therapy (PDT) was established as a successful modality for malignancies and age-related macular degeneration but photodynamic inactivation has only recently been intensively investigated as an alternative antimicrobial discovery and development platform. The concept of photodynamic inactivation requires microbial exposure to either exogenous or endogenous photosensitizer molecules, followed by visible light energy, typically wavelengths in the red/near infrared region that cause the excitation of the photosensitizers resulting in the production of singlet oxygen and other reactive oxygen species that react with intracellular components, and consequently produce cell inactivation and death. Antifungal PDT is an area of increasing interest, as research is advancing (i) to identify the photochemical and photophysical mechanisms involved in photoinactivation; (ii) to develop potent and clinically compatible photosensitizers; (iii) to understand how photoinactivation is affected by key microbial phenotypic elements multidrug resistance and efflux, virulence and pathogenesis determinants, and formation of biofilms; (iv) to explore novel photosensitizer delivery platforms; and (v) to identify photoinactivation applications beyond the clinical setting such as environmental disinfectants.

Photodynamic antifungal chemotherapy

The growing resistance against antifungal drugs has renewed the search for alternative treatment modalities, and antimicrobial photodynamic therapy (PDT) seems to be a potential candidate. Preliminary findings have demonstrated that dermatophytes and yeasts can be effectively sensitized in vitro and in vivo by administering photosensitizers (PSs) belonging to four chemical groups: phenothiazine dyes, porphyrins and phthalocyanines, as well as aminolevulinic acid, which, while not a PS in itself, is effectively metabolized into protoporphyrin IX. Besides efficacy, PDT has shown other benefits. First, the sensitizers used are highly selective, i.e., fungi can be killed at combinations of drug and light doses much lower than that needed for a similar effect on keratinocytes. Second, all investigated PSs lack genotoxic and mutagenic activity. Finally, the hazard of selection of drug resistant fungal strains has been rarely reported. We review the studies published to date on antifungal applications of PDT, with special focus on yeast, and aim to raise awareness of this area of research, which has the potential to make a significant impact in future treatment of fungal infections.

Substituted zinc phthalocyanine as an antimicrobial photosensitizer for periodontitis treatment

In the last decades the worldwide rise in antibiotic resistance has intensified the development of new antimicrobial agents. Photodynamic antimicrobial chemotherapy (PACT) has been used successfully to inactivate bacteria. We herein report a new zinc phthalocyanine based photosensitizer conjugated with polylysine moiety ( ZnPc-PL ). This photosensitizer significantly inactivated Porphyromonas gingivalis, the primary pathogenic bacteria responsible for periodontitis. No obvious phototoxicity was found to either mammalian bone marrow stromal cells (BMSC) or human periodontal ligament cells (HPDLC), indicating the high selectivity of ZnPc -PL toward bacteria. Furthermore, we established an experimental periodontitis model on beagle dogs to test the antimicrobial efficacy in vivo. The amount of gingival crevicular fluid (GCF) and the activity of crevicular fluid aspartate aminotransferase (AST) were monitored and were found to reduce significantly in the ZnPc-PL treated group compared to the controls (laser only and no treatment). In addition, PACT with ZnPc -PL caused a reduction in the bacterial burden by 100-fold compared to controls. Taken together, these findings suggest ZnPc-PL is a promising antimicrobial photosensitizer for the treatment of periodontal diseases.

Miconazole induces fungistasis and increases killing of Candida albicans subjected to photodynamic therapy

Cutaneous and mucocutaneous Candida infections are considered to be important targets for antimicrobial photodynamic therapy (PDT). Clinical application of antimicrobial PDT will require strategies that enhance microbial killing while minimizing damage to host tissue. Increasing the sensitivity of infectious agents to PDT will help achieve this goal. Our previous studies demonstrated that raising the level of oxidative stress in Candida by interfering with fungal respiration increased the efficiency of PDT. Therefore, we sought to identify compounds in clinical use that would augment the oxidative stress caused by PDT by contributing to reactive oxygen species (ROS) formation themselves. Based on the ability of the antifungal miconazole to induce ROS in Candida, we tested several azole antifungals for their ability to augment PDT in vitro. Although miconazole and ketoconazole both stimulated ROS production in Candida albicans, only miconazole enhanced the killing of C. albicans and induced prolonged fungistasis in organisms that survived PDT using the porphyrin TMP-1363 and the phenothiazine methylene blue as photosensitizers. The data suggest that miconazole could be used to increase the efficacy of PDT against C. albicans, and its mechanism of action is likely to be multifactorial.

Denture stomatitis treated with photodynamic therapy: five cases

OBJECTIVE

Photodynamic therapy (PDT) is an effective method for Candida spp. inactivation in vitro and in vivo, but as yet, no clinical trial has been conducted. This report describes 5 cases of denture stomatitis (DS) treated with PDT.

STUDY DESIGN

Five subjects with clinical and microbiologic diagnosis of DS were submitted to 6 sessions of PDT 3 times a week for 15 days. In each session, patients' dentures and palates were sprayed with 500 mg/L Photogem, and, after 30 minutes of incubation, irradiated by light-emitting diode light source at 455 nm (37.5 and 122 J/cm(2), respectively). Cultures of Candida spp. from dentures and palates and standard photographs of the palates were taken at baseline (day 0), at the end of the treatment (day 15), and at follow-up time intervals (days 30 and 60).

RESULTS

Four patients showed clinical resolution of DS (no inflammation) after PDT sessions, and only 1 subject demonstrated reduction in palatal inflammation. Recurrence of DS was observed in 2 patients during the follow-up period.

CONCLUSIONS

PDT appears to be an alternative treatment for DS.

Antimicrobial photodynamic therapy treatment of chronic recurrent sinusitis biofilms

BACKGROUND

Chronic recurrent sinusitis (CRS) is an inflammatory disease of the facial sinuses and nasal passages that is defined as lasting longer than 12 weeks or occurring more than 4 times per year with symptoms usually lasting more than 20 days. The National Institute for Health Statistics estimates that CRS is one of the most common chronic conditions in the United States, affecting an estimated 37 million Americans. The potential etiologies of CRS include bacteria, viruses, allergies, fungi, superantigens, and microbial biofilms. In clinical practice there is a significant subpopulation of patients with CRS who remain resistant to cure despite rigorous treatment regimens including surgery, allergy therapy, and prolonged antibiotic therapy. The reason for treatment failure is thought to be related to the destruction of the sinus mucociliary defense by the chronic sinus infection resulting in the development of secondary antibiotic-resistant microbial colonization of the sinuses and biofilm formation. Antimicrobial photodynamic therapy (aPDT) is a nonantibiotic broad-spectrum antimicrobial treatment that has been demonstrated to eradicate antibiotic-resistant bacteria and biofilms. The objective of this study was to demonstrate the effectiveness of a noninvasive aPDT treatment method of eradicating antibiotic resistant biofilms/microorganisms known to cause CRS in an in vitro model.

METHODS

Antibiotic-resistant planktonic bacteria and fungi and polymicrobial biofilms of Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) were grown on silastic sheets and treated with a methylene blue photosensitizer and 670 nm non-thermal-activating light. Cultures of the planktonic microorganisms and biofilms were obtained before and after light treatment to determine efficacy of planktonic bacteria and biofilm reduction.

RESULTS

The in vitro CRS planktonic microorganism and biofilm study demonstrated that aPDT reduced the CRS polymicrobial biofilm by >99.9% after a single treatment.

CONCLUSION

aPDT can effectively treat CRS polymicrobial antibiotic-resistant bacteria, fungi, and biofilms in vivo. Human clinical studies are currently planned to assess the safety and efficacy of this treatment for CRS.

Fungicidal effect of photodynamic therapy against fluconazole-resistant Candida albicans and Candida glabrata

Although photodynamic therapy (PDT) has shown great promise for the inactivation of Candida species, its effectiveness against azole-resistant pathogens remains poorly documented. This in vitro study describes the association of Photogem® (Photogem, Moscow, Russia) with LED (light emitting diode) light for the photoinactivation of fluconazole-resistant (FR) and American Type Culture Collection (ATCC) strains of Candida albicans and Candida glabrata. Suspensions of each Candida strain were treated with five Photogem® concentrations and exposed to four LED light fluences (14, 24, 34 or 50 min of illumination). After incubation (48 h at 37 °C), colonies were counted (CFU ml(-1)). Single-species biofilms were generated on cellulose membrane filters, treated with 25.0 mg l(-1) of Photogem® and illuminated at 37.5 J cm(-2). The biofilms were then disrupted and the viable yeast cells present were determined. Planktonic suspensions of FR strains were effectively killed after PDT. It was observed that the fungicidal effect of PDT was strain-dependent. Significant decreases in biofilm viability were observed for three strains of C. albicans and for two strains of C. glabrata. The results of this investigation demonstrated that although PDT was effective against Candida species, fluconazole-resistant strains showed reduced sensitivity to PDT. Moreover, single-species biofilms were less susceptible to PDT than their planktonic counterparts.

Evaluation of the effect of photoactivated disinfection with Radachlorin(®) against Streptococcus mutans (an in vitro study)

BACKGROUND

The use of photoactivated disinfection has had a significant medical and technological effect in bacterial inactivation, as an alternative to conventional antimicrobial methods. The main goal of this study was to investigate the effect of photoactivated disinfection on Streptococcus mutans, when Radachlorin(®) was used as a photosensitizer.

METHODS

Streptococcus mutans samples of two different initial concentrations were treated with Radachlorin(®) gel (0.1%), irradiated by the light of a He-Ne laser (633nm), with energy density of 6J/cm(2), and cell viability was evaluated after culturing.

RESULTS

It was observed that the combination of Radachlorin(®) and laser was more effective than Radachlorin(®) or laser alone (p<0.05), in reduction of S. mutans and Radachlorin(®) was cytotoxic, in the dark, only for the lower concentration of bacteria. Lower concentration of S. mutans resulted in higher amount of killing, in the case of using Radachlorin(®) with or without laser.

CONCLUSIONS

The photoactivation of Radachlorin(®) using a He-Ne laser could inactivate S. mutans to a significant level. In addition Radachlorin(®) might be cytotoxic in the dark, for the lower concentration of bacteria.

Effective photosensitization and selectivity in vivo of Candida Albicans by meso-tetra (N-methyl-4-pyridyl) porphine tetra tosylate

BACKGROUND AND OBJECTIVE

The fungus Candida albicans commonly causes mucosal and cutaneous infections in patients with impaired immunity. We investigated the effectiveness of the photosensitizer meso-tetra (N-methyl-4-pyridyl) porphine tetra tosylate (TMP-1363) in the photodynamic treatment (PDT) of C. albicans infection in vitro and its selectivity in an animal model.

MATERIALS AND METHODS

The efficacy of TMP-1363 in PDT of C. albicans in vitro was compared to that of methylene blue (MB) using a colony forming unit (CFU) assay. In vivo infection in the mouse was established by inoculation of C. albicans yeast in the intradermal space of the ear pinna. Two days post-infection, 0.3 mg ml(-1) TMP-1363 was administered topically. Thirty minutes after TMP-1363 application, the ears were irradiated at 514 nm using a fluence of 90 J cm(-2) delivered at an irradiance of 50 mW cm(-2) . The ears were excised 2 hours post-irradiation, homogenized, and the organism burden was determined by a CFU assay. In vivo wide field and confocal fluorescence imaging assessed the localization of the photosensitizer in relationship to C. albicans.

RESULTS

Photosensitization with TMP-1363 resulted in a greater than three-log increase in killing of C. albicans in vitro compared to MB. In vivo fluorescence imaging demonstrated a high degree of selective labeling of C. albicans by TMP-1363. PDT of infection using TMP-1363 resulted in a significant reduction in CFU/ear relative to untreated controls. Infected ears subjected to PDT displayed complete healing over time with no observable damage to the pinna.

CONCLUSION

Our in vitro and in vivo findings support TMP-1363-mediated PDT as a viable therapeutic approach for the PDT of candidiasis.

Cryptococcus gattii: in vitro susceptibility to photodynamic inactivation

Cryptococus gattii is an emergent primary human pathogen that causes meningismus, papilledema, high intracranial pressure and focal involvement of the central nervous system in immunocompetent hosts. Prolonged antifungal therapy is the conventional treatment, but it is highly toxic, selects for resistant strains, contributes to therapy failure and has a poor prognosis. Photodynamic inactivation (PDI) offers a promising possibility for the alternative treatment of cryptococcosis. The aim of this study was to test the effectiveness of toluidine blue O (TBO) and light-emitting diode (LED) against C. gattii strains with distinct susceptibility profile to antifungal drugs (amphotericin B: 0.015-1.0 μg mL(-1); itraconazole: 0.015-2 μg mL(-1); fluconazole: 4-64 μg mL(-1)). Using 25 μM (6.76 μg mL(-1)) TBO and LED energy density of 54 J cm(-2) these fungal isolates presented variable susceptibility to PDI. The production of reactive oxygen species (ROS)/peroxynitrite was determined, and the catalase and peroxidase activities were measured. After PDI, high amounts of ROS/peroxynitrite are produced and higher catalase and peroxidase activities could be correlated with a lower susceptibility of C. gattii isolates to PDI. These results indicate that PDI could be an alternative to C. gattii growth inhibition, even of isolates less susceptible to classical antifungal drugs, also pointing to mechanisms related to their variable susceptibility behavior.

Photodynamic inactivation of Acinetobacter baumannii using phenothiazinium dyes: in vitro and in vivo studies

BACKGROUND AND OBJECTIVE

Phenothiazinium dyes have been reported to be effective photosensitizers inactivating a wide range of microorganisms in vitro after illumination with red light. However, their application in vivo has not extensively been explored. This study evaluates the bactericidal activity of phenothiazinium dyes against multidrug-resistant Acinetobacter baumannii both in vitro and in vivo.

STUDY DESIGN/MATERIALS AND METHODS

We report the investigation of toluidine blue O, methylene blue, 1,9-dimethylmethylene blue, and new methylene blue for photodynamic inactivation of multidrug-resistant A. baumannii in vitro. The most effective dye was selected to carry out in vivo studies using third-degree mouse burns infected with a bioluminescent A. baumannii strain, upon irradiation with a 652 nm noncoherent light source. The mice were imaged daily for 2 weeks to observe differences in the bioluminescence-time curve between the photodynamic therapy (PDT)-treated mice in comparison with untreated burns.

RESULTS

All the dyes were effective in vitro against A. baumannii after 30 J/cm(2) irradiation of 635 or 652 nm red light had been delivered, with more effective killing when the dye remained in solution. New methylene blue was the most effective of the four dyes, achieving a 3.2-log reduction of the bacterial luminescence during PDT in vivo after 360 J/cm(2) and an 800 microM dye dose. Moreover, a statistically significant reduction of the area under the bioluminescence-time curve of PDT-treated mice was observed showing that the infection did not recur after PDT.

CONCLUSIONS

Phenothiazinium dyes, and especially new methylene blue, are potential photosensitizers for PDT to treat burns infected with multidrug-resistant A. baumannii in vivo.