Effect of different wavelengths and dyes on Candida albicans: In vivo study using Galleria mellonella as an experimental model

In vitro photodynamic therapy of Candida albicans, the cause of vulvovaginal candidiasis, is enhanced by Bacillus and Enterococcus probiotics

BACKGROUND

Candida albicans is the primary cause of vulvovaginal candidiasis, a worldwide health concern for women. The use of supplemental methods, such as antimicrobial photodynamic therapy (aPDT) and probiotics, was promoted by the ineffectiveness of the existing antifungal drugs.

METHODS

This study examines the combined effects of probiotics (Bacillus and Enterococcus isolated from the fermented pickles) and PDT (using red laser (655 nm, 18 J/cm2) as a light source and methylene blue dye (30 mg/mL) as a photosensitizer) on the in vitro virulence activity of C. albicans including growth, biofilm formation, antifungal resistance, biofilm elimination, and biofilm dispersion.

RESULTS

The probiotic strains demonstrated a higher resistance to PDT compared to the fungal cell. Bacillus and Enterococcus enhanced the antifungal effects of PDT on planktonic Candida cells in both pre-PDT and post-PDT interactions. The inhibition of biofilm formation by PDT was improved upon interaction with Bacillus (70 %) and Enterococcus (58 %). The eradication of Candida biofilm using PDT was increased after a combination with Bacillus (67 %) and Enterococcus (46 %). The nystatin resistance of the fungal biofilm following PDT treatment was decreased from (µg/ml) 25 to 6.25 due to the interaction with both probiotic strains. Fungal cell dispersion from the biofilm after PDT treatment diminished by 18 % and 25 % in the presence of Bacillus and Enterococcus strains. Galleria mellonella mortality was significantly changed following the PDT of the fungi/probiotic-injected larvae.

CONCLUSIONS

This synergistic activity suggests the use of probiotics/PDT as a supplemental treatment for vulvovaginal candidiasis.

Efficacy of Curcumin-Mediated Antimicrobial Photodynamic Therapy on Candida spp.-A Systematic Review

Oral candidiasis is a common problem among immunocompetent patients. The frequent resistance of Candida strains to popular antimycotics makes it necessary to look for alternative methods of treatment. The authors conducted a systematic review following the PRISMA 2020 guidelines. The objective of this review was to determine if curcumin-mediated blue light could be considered as an alternative treatment for oral candidiasis. PubMed, Google Scholar, and Cochrane Library databases were searched using a combination of the following keywords: (Candida OR candidiasis oral OR candidiasis oral OR denture stomatitis) AND (curcumin OR photodynamic therapy OR apt OR photodynamic antimicrobial chemotherapy OR PACT OR photodynamic inactivation OR PDI). The review included in vitro laboratory studies with Candida spp., in vivo animal studies, and randomized control trials (RCTs) involving patients with oral candidiasis or prosthetic stomatitis, published only in English. The method of elimination of Candida species in the studies was curcumin-mediated aPDT. A total of 757 studies were identified. Following the analysis of the titles and abstracts of the studies, only 42 studies were selected for in-depth screening, after which 26 were included in this study. All studies evaluated the antifungal efficacy of curcumin-mediated aPDT against C. albicans and non-albicans Candida. In studies conducted with planktonic cells solutions, seven studies demonstrated complete elimination of Candida spp. cells. The remaining studies demonstrated only partial elimination. In all cases, experiments on single-species yeast biofilms demonstrated partial, statistically significant inhibition of cell growth and reduction in biofilm mass. In vivo, curcumin-mediated aPDT has shown good antifungal activity against oral candidiasis also in an animal model. However, its clinical efficacy as a potent therapeutic strategy for oral candidiasis requires few further RCTs.

Photoinactivation Effects of Curcumin, Nano-curcumin, and Erythrosine on Planktonic and Biofilm Cultures of Streptococcus mutans

Introduction: This in vitro study was conducted to assess the phototoxic effects of curcumin, nano-curcumin, and erythrosine on the viability of Streptococcus mutans (S. mutans) in suspension and biofilm forms. Methods: Various concentrations of curcumin (1.5 g/L, 3 g/L), nano-curcumin (3 g/L), and erythrosine (100 μM/L, 250 μM/L) were examined for their impact on planktonic and biofilm cultures of S. mutans, either individually or in conjunction with light irradiation (photodynamic therapy or PDT). A blue light-emitting diode (LED) with a central wavelength of 450 nm served as the light source. The results were compared to 0.12% chlorhexidine digluconate (CHX) as the positive control, and a solution containing neither a photosensitizer (PS) nor a light source as the negative control group. The dependent variable was the number of viable microorganisms per experiment (CFU/mL). Results: Antimicrobial PDT caused a significant reduction in the viability of S. mutans in both planktonic and biofilm forms, compared to the negative control group (P<0.05). The highest cell killing was observed in PDT groups with curcumin 3 g/L or erythrosine 250 μmol/L, although the difference with PDT groups using curcumin 1.5 g/L or erythrosine 100 μmol/L was not significant (P>0.05). Antimicrobial treatments were more effective against planktonic S. mutans than the biofilm form. Conclusion: PDT with either curcumin 1.5 g/L or erythrosine 100 μmol/L may be suggested as an alternative to CHX to inactivate the bacteria in dental plaque or deep cavities. Nano-curcumin, at the selected concentration, exhibited lower efficacy in killing S. mutans compared to Curcumin or erythrosine.

Galleria mellonella-A Model for the Study of aPDT-Prospects and Drawbacks

Galleria mellonella is a promising in vivo model insect used for microbiological, medical, and pharmacological research. It provides a platform for testing the biocompatibility of various compounds and the kinetics of survival after an infection followed by subsequent treatment, and for the evaluation of various parameters during treatment, including the host-pathogen interaction. There are some similarities in the development of pathologies with mammals. However, a limitation is the lack of adaptive immune response. Antimicrobial photodynamic therapy (aPDT) is an alternative approach for combating microbial infections, including biofilm-associated ones. aPDT is effective against Gram-positive and Gram-negative bacteria, viruses, fungi, and parasites, regardless of whether they are resistant to conventional treatment. The main idea of this comprehensive review was to collect information on the use of G. mellonella in aPDT. It provides a collection of references published in the last 10 years from this area of research, complemented by some practical experiences of the authors of this review. Additionally, the review summarizes in brief information on the G. mellonella model, its advantages and methods used in the processing of material from these larvae, as well as basic knowledge of the principles of aPDT.

Photodynamic therapy-a promising treatment of oral mucosal infections

The treatment of oral mucosal infections is increasingly challenging owing to antibiotic resistance. Therefore, alternative antimicrobial strategies are urgently required. Photodynamic therapy (PDT) has attracted attention for the treatment of oral mucosal infections because of its ability to effectively inactivate drug-resistant bacteria, completely heal clinical infectious lesions and usually offers only mild adverse reactions. This review briefly summarizes relevant scientific data and published papers and discusses the potential mechanism and application of PDT in the treatment of oral mucosal infections.

In Vitro and In Vivo Anti-infective Potential of Thymol Against Early Childhood Caries Causing Dual Species Candida albicans and Streptococcus mutans

Early childhood caries (ECC), a severe form of caries due to cross-kingdom interaction of Candida albicans and Streptococcus mutans, is a serious childhood dental disease that affects majority of the children with poor background. The present study investigated the anti-infective potential of thymol against C. albicans and S. mutans dual species for the management of ECC. Thymol, a plant derivative of the monoterpene group, has been well known for its numerous biological activities. Thymol at 300 μg/ml concentration completely arrested growth and proliferation of dual species of C. albicans and S. mutans. Rapid killing efficacy of pathogens, within a span of 2 min, was observed in the time kill assay. In addition, at sub-inhibitory concentrations, thymol effectively diminished the biofilm formation and virulence of both C. albicans and S. mutans such as yeast-to-hyphal transition, hyphal-to-yeast transition, filamentation, and acidogenicity and acidurity, respectively, in single and dual species state. qPCR analysis was consistent with virulence assays. Also, through the invertebrate model system Galleria mellonella, in vivo toxicity and efficacy of the phytocompound was assessed, and it was found that no significant toxic effect was observed. Moreover, thymol was found to be proficient in diminishing the infection under single and dual state in in vivo condition. Overall, the results from the present study illustrate the anti-infective potential of thymol against the ECC-causing dual species, C. albicans and S. mutans, and the applicability of thymol in medicated dentifrice formulation.

Use of Blue and Blue-Violet Lasers in Dentistry: A Narrative Review

Introduction: Blue and blue-violet diode lasers (450 and 405 nm) seem to represent an interesting approach for several clinical treatments today. The aim of this narrative review is to describe and comment on the literature regarding the utilization of blue and blue-violet lasers in dentistry. Methods: A search for "blue laser AND dentistry" was conducted using the PubMed database, and all the papers referring to this topic, ranging from 1990 to April 2020, were analyzed in the review. All the original in vivo and in vitro studies using 450 nm or 405 nm lasers were included in this study. All the articles on the LED light, laser wavelengths other than 405 and 450 nm and using lasers in specialties other than dentistry, as well as case reports, guideline papers and reviews were excluded. Results: From a total of 519 results, 47 articles met the inclusion criteria and were divided into 8 groups based on their fields of application: disinfection (10), photobiomodulation (PBM) (4), bleaching (1), resin curing (20), surgery (7), periodontics (1), endodontics (1) and orthodontics (3). Conclusion: Blue and blue-violet diode lasers may represent new and effective devices to be used in a large number of applications in dentistry, even if further studies will be necessary to fully clarify the potentialities of these laser wavelengths.

pH interferes in photoinhibitory activity of curcumin nanoencapsulated with pluronic® P123 against Staphylococcus aureus

Microbial contamination control is a public health concern and challenge for the food industry. Antimicrobial technologies employing natural agents may be useful in the food industry for these purposes. This work aimed to investigate the effect of photodynamic inactivation using curcumin in Pluronic® P123 nanoparticles (Cur/P123) at different pH and blue LED light against Staphylococcus aureus. Bacterial photoinactivation was conducted using different photosensitizer concentrations and exposure times at pH 5.0, 7.2 and 9.0. A mixture design was applied to evaluate the effects of exposure time (dark and light incubation) on the photoinhibitory effect. S. aureus was completely inactivated at pH 5.0 by combining low concentrations of Cur/P123 (7.80-30.25 μmol/L) and light doses (6.50-37.74 J/cm²). According to the mathematical model, dark incubation had low significance in bacterial inactivation at pH 5.0 and 9.0. No effect in bacterial inactivation was observed at pH 7.2. Cur/P123 with blue LED was effective in inactivating S. aureus. The antimicrobial effect of photodynamic inactivation was also pH-dependent.

Focal Infection and Periodontitis: A Narrative Report and New Possible Approaches

The "focal infection theory" is a historical concept based on the assumption that some infections may cause chronic and acute diseases in different districts of the body. Its great popularity spanned from 1930 to 1950 when, with the aim to remove all the foci of infection, drastic surgical interventions were performed. Periodontitis, a common oral pathology mainly of bacterial origin, is the most evident example of this phenomenon today: in fact, bacteria are able to migrate, develop and cause health problems such as cardiovascular and respiratory diseases, diabetes, and osteoporosis. The aim of this narrative report is to verify the hypothesis of the association between oral infections and systemic diseases by different ways of approach and, at the same time, to propose new kinds of treatment today made possible by technological progress. The analysis of the literature demonstrated a strong relationship between these conditions, which might be explained on the basis of the recent studies on microbiota movement inside the body. Prevention of the oral infections, as well as of the possible systemic implications, may be successfully performed with the help of new technologies, such as probiotics and laser.

Exploring the Galleria mellonella model to study antifungal photodynamic therapy

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) shows antimicrobial activity on yeast of the genus Candida. In aPDT, the depth at which the light penetrates the tissue is extremely important for the elaboration of the treatment. The aim of this study was to evaluate the action of aPDT on experimental candidiasis and the laser impact in the tissue using Galleria mellonella as the infection model.

METHODS

G. mellonella larvae were infected with different Candida albicans strains. After 30 min, they were treated with methylene blue-mediated aPDT and a low intensity laser (660 nm). The larvae were incubated at 37 °C for seven days and monitored daily to determine the survival curve, using the Log-rank test (Mantel Cox). To evaluate the distribution of the laser as well as its depth of action in the larva body, the Interactive 3D surface PLOT of Image J was used. The effects of aPDT on the immune system were also evaluated by the quantification of hemocytes in the hemolymph of G. mellonella after 6 h of Candida infection (ANOVA and Tukey's test).

RESULTS

In both the ATCC 18,804 strain and the C. albicans clinical strain 17, aPDT prolonged the survival of the infected G. mellonella larvae by a lethal fungal dose. There was a statistically significant difference between the aPDT and the control groups in the ATCC strain (P = 0.0056). The depth of laser action in the insect body without the photosensitizer was 2.5 mm and 2.4 mm from the cuticle of the larva with the photosensitizer. In the larvae, a uniform distribution of light occurred along 32% of the body length for the group without the photosensitizer and in 39.5% for the group with the photosensitizer. In the immunological analysis, the infection by C. albicans ATCC 18,804 in G. mellonella led to a reduction in the number of hemocytes in the hemolymph. The aPDT and laser treatment induced a slight increase in the number of hemocytes.

CONCLUSION

Both aPDT and laser treatment positively influenced the treatment of experimental candidiasis. G. mellonella larvae were a useful model for the study of light tissue penetration in antimicrobial photodynamic therapy.

Antimicrobial Photodynamic Therapy Protocols on Streptococcus mutans with Different Combinations of Wavelengths and Photosensitizing Dyes

The aim of the study is to test the application of different laser wavelengths, with and without different photosensitizing dyes on different types of cultures. Laser irradiation was realized on Streptococcus mutans in both solid and liquid culture media in continuous mode at three different fluences (10, 20, and 30 J/cm2) with a red diode (650 nm) with toluidine blue dye, a blue-violet diode (405 nm) with curcumin dye, and a green diode (532 nm) with erythrosine dye. Without a photosensitizer, no growth inhibition was obtained with the red diode at any fluence value. Inhibition rates of 40.7% and 40.2% were obtained with the blue diode and green diode. The blue diode laser used with curcumin obtained results in terms of growth inhibition up to 99.26% at a fluence of 30 J/cm2. The red diode laser used with toluidine blue obtained results in terms of growth inhibition up to 100% at fluences of 20 and 30 J/cm2. The KTP (potassium-titanyl-phosphate) laser used with erythrosine was able to determine a complete growth inhibition (100%) at the different fluence values. The combination of a laser and its proper color may dramatically change the results in terms of bactericidal effect. It will be interesting to confirm these data by further in vivo studies.

Antimicrobial effect on Candida albicans biofilm by application of different wavelengths and dyes and the synthetic killer decapeptide KP

The aim of this study was to test the application in vitro of different laser wavelengths at a low fluence in combination or not with proper photosensitizing dyes on Candida albicans biofilm with or without a synthetic killer decapeptide (KP). Candida albicans SC5314 was grown on Sabouraud dextrose agar plates at 37°C for 24 h. Cells were suspended in RPMI 1640 buffered with MOPS and cultured directly on the flat bottom of 96-wells plates. The previously described killer decapeptide KP was used in this study. Three different combinations of wavelengths and dyes were applied, laser irradiation has been performed at a fluence of 10 J/cm². The effect on C. albicans biofilm was evaluated by the XTT assay. Microscopic observations were realized by fluorescence optic microscopy with calcofluor white and propidium iodide. Compared with control, no inhibition of C. albicans biofilm viability was obtained with application of red, blue and green lasers alone or with any combination of red diode laser, toluidine blue and KP. The combined application of blue diode laser with curcumin and/or KP showed always a very significant inhibition, as curcumin alone and the combination of curcumin and KP did, while combination of blue diode laser and KP gave a less significant inhibition, the same obtained with KP alone. The combined application of green diode laser with erythrosine and/or KP showed always a very significant inhibition, as the combination of erythrosine and KP did, but no difference was observed with respect to the treatment with erythrosine alone. Again, combination of green diode laser and KP gave a significant inhibition, although paradoxically lower than the one obtained with KP alone. Treatment with KP alone, while reducing biofilm viability did not cause C. albicans death in the adopted experimental conditions. On the contrary, combined treatment with blue laser, curcumin and KP, as well as green laser, erythrosine and KP led to death most C. albicans cells. The combination of laser light at a fluence of 10 J/cm² and the appropriate photosensitizing agent, together with the use of KP, proved to exert differential effects on C. albicans biofilm.

In vitro photodynamic inactivation effects of benzylidene cyclopentanone photosensitizers on clinical fluconazole-resistant Candida albicans

BACKGROUND

The incidence of Candida infections has increased for various reasons, including, the more frequent use of immunosuppresants or broad-spectrum antibiotics. Photodynamic inactivation (PDI) is a promising approach for treating localized Candida infections.

METHODS

The PDI efficacies of three benzylidene cyclopentanone-based (BCB) photosensitizers (PSs: P1, P2 and Y1) against three fluconazole-resistant C. albicans (cal-1, cal-2, and cal-3) and one control C. albicans (ATCC 90028), respectively, were evaluated using an established plate dilution method. The binding of PSs to C. albicans was determined by fluorescence spectroscopy. The mechanism of antifungal PDI was investigated using confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM).

RESULTS

Three BCB PSs all bound rapidly to C. albicans. After incubation with PSs for 30 min and irradiation with a 532 nm laser for 10 min (40 mW cm^-2, 24 J cm^-2), the fungicidal activity was achieved as 7.5 μM for P1 and P2, and 25 μM for Y1. CLSM confirmed that P1 and Y1 were located in intracellular components, including mitochondria, while P2 bound to the protoplast exterior and failed to enter the cells. TEM revealed the damage of mitochondria ultrastructures after P1- or Y1-mediated PDI, consistenting with the CLSM results. However, most cells became edematous, enlarged or deformation after P2-mediated PDI.

CONCLUSIONS

The three BCB PSs all have remarkable PDI effects on C. albicans. The best effect is obtained by P1, which has one cationic charge with a proper lipophilicity. The respective subcellular localization of the three PSs led to different PDI mechanisms.