Clinical outcomes of Rose Bengal mediated Photodynamic Antimicrobial Therapy on Fungal Keratitis with their microbiological and pathological correlation

Alternative photosensitizer penetration depth evaluation in ex vivo human eyes for photodynamic antimicrobial therapy

PURPOSE

Fungal keratitis has a poor prognosis given deep penetration into the corneal stroma. While Rose Bengal photodynamic antimicrobial therapy (RB-PDAT) is a promising adjunct treatment for refractory cases, poor penetration limits its effectiveness. This study explores the penetration depth of alternative photosensitizers to address this issue.

METHODS

Thirty-five human corneas were soaked for 30 minutes in 0.0075% solution of Rose Bengal disodium (n = 5), Rose Bengal lactone (n = 5), Erythrosin B disodium (n = 5), Erythrosin B lactone (n = 5), Eosin Y disodium (n = 5), Methylene blue (n = 5), or NaCl (control, n = 5). Confocal microscopy was used to assess penetration depth.

RESULTS

All photosensitizers penetrated greater into the cornea as compared to control. There was no significant difference in penetration between Rose Bengal lactone and Rose Bengal disodium (RB lactone: 106  ± 11 µm vs RB disodium: 99 ± 13 µm, p > 0.05). The penetration depths of the alternative photosensitizers was significantly greater than either Rose Bengal formulation (Erythrosin Blactone: 192 ± 31 µm, Erythrosin B disodium: 163 ± 13 µm, Eosin Y disodium: 249 ± 31 µm, Methylene Blue: 355 ± 151 µm).

CONCLUSIONS

Alternative photosensitizers exhibit superior penetration compared to Rose Bengal. However, antimicrobial efficacy and corneal safety require more robust evaluation before clinical use.

Photodynamic antimicrobial therapy with Erythrosin B, Eosin Y, and Rose Bengal for the inhibition of fungal keratitis isolates: An in vitro study

INTRODUCTION

Fungal keratitis is a leading cause of corneal blindness, with current antifungal treatments having limited efficacy. One promising treatment modality is Rose Bengal (RB) photodynamic antimicrobial therapy (PDAT) that has shown mixed success against fungal keratitis. Therefore, there is a need to explore the antimicrobial efficacy of other green-light activated photosensitizers that have deep penetration in the cornea to combat the deep fungal infections, such as Erythrosin B (EB) and Eosin Y (EY).

OBJECTIVE

This study will explore PDAT inhibitory effects with different photosensitizers, RB, EB, and EY against two common fungal ocular isolates, Aspergillus spp. and Fusarium spp.

METHODS

Twelve fungal isolates (Fusarium spp., n = 6, Aspergillus spp., n = 6) were prepared in suspension for evaluation of growth inhibition to PDAT with three photosensitizers, EB, EY, and RB. Custom green light source (λ = 518 nm, energy density = 5.4 J/cm2) was applied to the experimental groups for 15 min. Fungal growth inhibition was assessed after experimentation by analyzing the area of growth within the irradiated zone on agar plates.

RESULTS

All twelve fungal isolates showed no inhibition to EB, EY, and RB without irradiation. Fusarium spp. were more susceptible to PDAT than Aspergillus spp. In all Fusarium solani strains, all photosensitizers with light showed full inhibition within the 47 mm diameter irradiation zone.

CONCLUSION

EB, EY, and RB PDAT demonstrated comparable antifungal inhibition against six Fusarium ocular isolates; these findings in conjunction with the deeper tissue penetration of EB and EY, are of interest to treat more advanced and deeper cases of fungal keratitis.

The cellular response of lipopolysaccharide-induced inflammation in keratoconus human corneal fibroblasts to RB-PDT: Insights into cytokines, chemokines and related signaling pathways

PURPOSE

Rose Bengal Photodynamic Therapy (RB-PDT) offers dual therapeutic benefits by enhancing corneal stiffness and providing antibacterial activity, presenting significant potential for patients with keratoconus complicated by keratitis. Our purpose was to assess the effect of rose bengal photodynamic therapy (RB-PDT) on the expression of pro-inflammatory cytokines and chemokines, as well as on extracellular matrix (ECM)-related molecules, in lipopolysaccharide (LPS)-induced inflammation of keratoconus human corneal fibroblasts (KC-HCFs). Additionally, the involvement of the mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) signaling pathways which are downstream of the Toll-like receptor 4 (TLR4) pathway were examined.

METHODS

KC-HCFs were stimulated with varying concentrations of LPS (0-10 μg/ml), which was followed by RB-PDT. The expression levels of interleukin-1β (IL-1β), IL-6, IL-8, interferon alpha 2 (IFNA2), IFNB1, intercellular adhesion molecule 1 (ICAM-1), chemokine (C-C motif) ligand 4 (CCL-4), collagen I, collagen V, lysyl oxidase (LOX), transforming growth factor β 1(TGF-β1) were measured using qPCR, ELISA, or western blot. The activation of the NF-κB and MAPK pathways was assessed using qPCR and western blot.

RESULTS

In LPS-induced inflammation of KC-HCFs, the expression of IL-6 was further amplified by the treatment with RB-PDT (p = 0.001). However, the activation of the MAPK and NF-κB pathways did not increase following RB-PDT. Additionally, RB-PDT reduced the transcription of collagen I and collagen V (p≤0.03), while the transcription of LOX and TGF-β1 secretion remained unchanged in KC-HCFs exposed to LPS.

CONCLUSION

In LPS-induced inflammation of KC-HCFs treated with RB-PDT, despite the increased expression of pro-inflammatory cytokines, the activation of the TLR4 signaling pathways is lacking. RB-PDT may have no adverse effects on corneal scar formation of keratoconus corneas in the short term.

Antifungal efficacy of photodynamic therapy on Cryptococcus and Candida species is enhanced by Streptomyces spp. extracts in vitro

The research on actinobacteria isolated from traditional medicinal plants is limited. Here, four new Streptomyces isolates (Ha1, Pp1, UzK and UzM) were obtained from the rhizospheres of Helianthus annuus, Pongamia pinnata and Ziziphus mauritiana, frequently utilized in Indian traditional medicine. The Streptomyces isolates aqueous extracts were studied alone against the growth of the Cryptococcus neoformans H99 reference strain, the fluconazole-tolerant T1-5796 and 89-610 strains, three histone deacetylase (HDAC) genes mutant strains, C. gattii NIH198, Candida albicans, C. glabrata, C. parapsilosis and C. tropicalis to determine minimum inhibitory concentration (MIC). Next, the extracts were employed in combination with aluminium-phthalocyanine chloride nanoemulsion-mediated photodynamic therapy to evaluate a possible interaction. We demonstrated that the C. neoformans T1-5796 fluconazole-tolerant strain was more severely inhibited by the Pp1 isolate extract (MIC: 6 mg mL-1) than H99, which was not inhibited. Growth inhibition of the HDAC null mutants was more prominent for the extract of the UzM isolate, showing inhibition at 2 mg mL-1. The UzM extract was also the most effective in hindering the Candida species proliferation, with MIC values ranging from 10 to 40 mg mL-1. The four Streptomyces extracts, especially UzK and UzM, significantly enhanced the antifungal effect of the photodynamic therapy. Our results indicate these Streptomyces isolates as sources of novel metabolites which could potentiate the effect of photodynamic therapy in controlling yeasts superficial infections.

Overview of Mycotic Keratitis

ABSTRACT

Keratomycosis is a serious corneal infection associated with high ocular morbidity that can lead to severe vision loss. It is estimated to affect more than 1 million patients annually, most commonly occurring in tropical climates, and represents a growing threat to patients worldwide. Despite aggressive medical management, fungal infections have a higher rate of perforation requiring surgical intervention compared with other infectious etiologies. Early diagnosis and appropriate treatment are keys to preserving vision and saving patients' eyes.Timely diagnosis of fungal keratitis helps minimize corneal damage and scarring and increases the likelihood of a favorable outcome. Studies have shown that correct identification of fungal infections is often delayed up to 2 to 3 weeks after initial presentation. This leads to incorrect or ineffective treatment for many patients. Diagnostic techniques explored in this study include corneal scrapings with staining and culture, visualization with in vivo confocal microscopy, molecular diagnostic techniques including polymerase chain reaction, and recently developed omics-based technologies.Treatment of fungal keratitis begins with topical antifungals. Medical management has been proven to be effective, but with limitations including poor drug penetration and low bioavailability. Cases that do not respond to topical therapy require more invasive and novel treatments to control the infection. We review the clinical trials that have shaped current practice patterns, with focus on the efficacy of topical natamycin as the primary therapy for filamentous fungal keratitis. We explore additional management strategies such as localized intrastromal and intracameral injections of antifungal medications, photodynamic therapy, and surgical intervention.

Rose Bengal Photodynamic Therapy (RB-PDT) Modulates the Inflammatory Response in LPS-Stimulated Human Corneal Fibroblasts By Influencing NF-κB and p38 MAPK Signaling Pathways

PURPOSE

To investigate the effect of rose bengal photodynamic therapy on lipopolysaccharide-induced inflammation in human corneal fibroblasts. Furthermore, to analyze potential involvement of the mitogen-activated protein kinase and nuclear factor kappa B signaling pathways in this process.

METHODS

Human corneal fibroblast cultures underwent 0-2.0 µg/mL lipopolysaccharide treatment, and 24 h later rose bengal photodynamic therapy (0.001% RB, 565 nm wavelength illumination, 0.17 J/cm2 fluence). Interleukin-6, interleukin-8, intercellular adhesion molecule-1, interferon regulatory factor-3, interferon α2, and interferon β1 gene expressions were determined by quantitative PCR. Interleukin-6, interleukin-8, and C-C motif chemokine ligand-4 concentrations in the cell culture supernatant were measured by enzyme-linked immunosorbent assays and intercellular adhesion molecule-1 protein level in human corneal fibroblasts by western blot. In addition, the nuclear factor kappa B and mitogen-activated protein kinase signaling pathways were investigated by quantitative PCR and phosphorylation of nuclear factor kappa B p65 and p38 mitogen-activated protein kinase by western blot.

RESULTS

Rose bengal photodynamic therapy in 2.0 µg/mL lipopolysaccharide-stimulated human corneal fibroblasts triggered interleukin-6 and interleukin-8 mRNA (p < .0001) and interleukin-6 protein increase (p < .0001), and downregulated intercellular adhesion molecule-1 expression (p < .001). C-C motif chemokine ligand-4, interferon regulatory factor-3, interferon α2, and interferon β1 expressions remained unchanged (p ≥ .2). Rose bengal photodynamic therapy increased IκB kinase subunit beta, nuclear factor kappa B p65, extracellular signal-regulated kinases-2, c-Jun amino terminal kinase, and p38 transcription (p ≤ .01), and triggered nuclear factor kappa B p65 and p38 mitogen-activated protein kinase phosphorylation (p ≤ .04) in lipopolysaccharide treated human corneal fibroblasts.

CONCLUSION

Rose bengal photodynamic therapy of lipopolysaccharide-stimulated human corneal fibroblasts can modify the inflammatory response by inducing interleukin-6 and interleukin-8 expression, and decreasing intercellular adhesion molecule-1 production. C-C motif chemokine ligand-4, interferon regulatory factor-3, and interferon α and β expressions are not affected by rose bengal photodynamic therapy in these cells. The underlying mechanisms may be associated with nuclear factor kappa B and p38 mitogen-activated protein kinase pathway activation.

Variations in irradiation energy and rose bengal concentration for photodynamic antimicrobial therapy of fungal keratitis isolates

The purpose is to assess the efficacy of rose bengal photodynamic antimicrobial therapy (PDAT) using different irradiation energy levels and photosensitizer concentrations for the inhibition of fungal keratitis isolates. Seven different fungi (Aspergillus fumigatus, Candida albicans, Curvularia lunata, Fusarium keratoplasticum, Fusarium solani, Paecilomyces variotii, and Pseudallescheria boydii) were isolated from patients with confirmed infectious keratitis. Experiments were performed in triplicate with suspensions of each fungus exposed to different PDAT parameters including a control, green light exposure of 5.4 J/cm2, 2.7 J/cm2 (continuous and pulsed), and 1.8 J/cm2 and rose bengal concentrations of 0.1%, 0.05%, and 0.01%. Plates were photographed 72 h after experimentation, and analysis was performed to assess fungal growth inhibition. PDAT using 5.4 J/cm2 of irradiation and 0.1% rose bengal completely inhibited growth of five of the seven fungal species. Candida albicans and Fusarium keratoplasticum were the most susceptible organisms, with growth inhibited with the lowest fluence and minimum rose bengal concentration. Fusarium solani, Pseudallescheria boydii, and Paecilomyces variotii were inhibited by lower light exposures and photosensitizer concentrations. Aspergillus fumigatus and Curvularia lunata were not inhibited by any PDAT parameters tested. Continuous and pulsed irradiation using 2.7 J/cm2 produced similar results. Rose bengal PDAT successfully inhibits the in vitro growth of five fungi known to cause infectious keratitis. Differences in growth inhibition of the various fungi to multiple PDAT parameters suggest that susceptibilities to PDAT are unique among fungal species. These findings support modifying PDAT parameters based on the infectious etiology.