The effect of photodynamic action on two virulence factors of gram-negative bacteria

Effect of nonsurgical periodontal therapy with additional photodynamic therapy on the level of MMP-9 and TIMP-1 in GCF in chronic periodontitis patients-a preliminary pilot study

PURPOSE

Matrix metalloproteinases (MMPs) catalyze degradation of extracellular matrix proteins. The activity of MMPs is controlled by tissue inhibitors of metalloproteinases (TIMPs). An imbalance in the MMP-9/TIMP-1 ratio has been linked with chronic periodontitis (CP). Photodynamic therapy (PDT) uses visible light, photosensitizer and oxygen to eradicate pathogens. The aim of the study was to evaluate the presence of MMP-9 and TIMP-1 in gingival crevicular fluid (GCF) in chronic periodontitis patients before and after nonsurgical periodontal therapy with additional PDT.

METHODS

Nineteen patients, each with CP, were included in the study. After periodontal examination one site with a probing depth (PD) ​≥ ​4 ​mm was selected. The patients received scaling and root planing (SRP) with additional PDT by means of HELBO® diode minilaser. Prior to treatment, and after 3 and 6 months, the following parameters were estimated from the same site: PD, gingival recession (GR), clinical attachment level (CAL), plaque index (PI), bleeding on probing (BOP) and sulcus fluid flow rate (SFFR). The levels of MMP-9 and TIMP-1 in GCF were determined.

RESULTS

Compared to baseline, the levels of MMP-9 and TIMP-1 did not show statistically significant differences after 3 and 6 months. According to Spearman's rank correlations, MMP-9 was positively correlated with SFFR at all time points. PD, CAL and PI showed a statistically significant decrease compared to baseline (p ​< ​0.001). SFFR decreased but not significantly.

CONCLUSION

Nonsurgical periodontal therapy in conjunction with PDT was clinically effective but it had no effect on the levels of MMP-9 and TIMP-1 in GCF.

Adjunctive antimicrobial photodynamic therapy for treating periodontal and peri-implant diseases

BACKGROUND

Periodontitis and peri-implant diseases are chronic inflammatory conditions occurring in the mouth. Left untreated, periodontitis progressively destroys the tooth-supporting apparatus. Peri-implant diseases occur in tissues around dental implants and are characterised by inflammation in the peri-implant mucosa and subsequent progressive loss of supporting bone. Treatment aims to clean the pockets around teeth or dental implants and prevent damage to surrounding soft tissue and bone, including improvement of oral hygiene, risk factor control (e.g. encouraging cessation of smoking) and surgical interventions. The key aspect of standard non-surgical treatment is the removal of the subgingival biofilm using subgingival instrumentation (SI) (also called scaling and root planing). Antimicrobial photodynamic therapy (aPDT) can be used an adjunctive treatment to SI. It uses light energy to kill micro-organisms that have been treated with a light-absorbing photosensitising agent immediately prior to aPDT.

OBJECTIVES

To assess the effects of SI with adjunctive aPDT versus SI alone or with placebo aPDT for periodontitis and peri-implant diseases in adults.

SEARCH METHODS

We searched the Cochrane Oral Health Trials Register, CENTRAL, MEDLINE, Embase, two other databases and two trials registers up to 14 February 2024.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) (both parallel-group and split-mouth design) in participants with a clinical diagnosis of periodontitis, peri-implantitis or peri-implant disease. We compared the adjunctive use of antimicrobial photodynamic therapy (aPDT), in which aPDT was given after subgingival or submucosal instrumentation (SI), versus SI alone or a combination of SI and a placebo aPDT given during the active or supportive phase of therapy.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures, and we used GRADE to assess the certainty of the evidence. We prioritised six outcomes and the measure of change from baseline to six months after treatment: probing pocket depth (PPD), bleeding on probing (BOP), clinical attachment level (CAL), gingival recession (REC), pocket closure and adverse effects related to aPDT. We were also interested in change in bone level (for participants with peri-implantitis), and participant satisfaction and quality of life.

MAIN RESULTS

We included 50 RCTs with 1407 participants. Most studies used a split-mouth study design; only 18 studies used a parallel-group design. Studies were small, ranging from 10 participants to 88. Adjunctive aPDT was given in a single session in 39 studies, in multiple sessions (between two and four sessions) in 11 studies, and one study included both single and multiple sessions. SI was given using hand or power-driven instrumentation (or both), and was carried out prior to adjunctive aPDT. Five studies used placebo aPDT in the control group and we combined these in meta-analyses with studies in which SI alone was used. All studies included high or unclear risks of bias, such as selection bias or performance bias of personnel (when SI was carried out by an operator aware of group allocation). We downgraded the certainty of all the evidence owing to these risks of bias, as well as for unexplained statistical inconsistency in the pooled effect estimates or for imprecision when evidence was derived from very few participants and confidence intervals (CI) indicated possible benefit to both intervention and control groups. Adjunctive aPDT versus SI alone during active treatment of periodontitis (44 studies) We are very uncertain whether adjunctive aPDT during active treatment of periodontitis leads to improvement in any clinical outcomes at six months when compared to SI alone: PPD (mean difference (MD) 0.52 mm, 95% CI 0.31 to 0.74; 15 studies, 452 participants), BOP (MD 5.72%, 95% CI 1.62 to 9.81; 5 studies, 171 studies), CAL (MD 0.44 mm, 95% CI 0.24 to 0.64; 13 studies, 414 participants) and REC (MD 0.00, 95% CI -0.16 to 0.16; 4 studies, 95 participants); very low-certainty evidence. Any apparent differences between adjunctive aPDT and SI alone were not judged to be clinically important. Twenty-four studies (639 participants) observed no adverse effects related to aPDT (moderate-certainty evidence). No studies reported pocket closure at six months, participant satisfaction or quality of life. Adjunctive aPDT versus SI alone during supportive treatment of periodontitis (six studies) We were very uncertain whether adjunctive aPDT during supportive treatment of periodontitis leads to improvement in any clinical outcomes at six months when compared to SI alone: PPD (MD -0.04 mm, 95% CI -0.19 to 0.10; 3 studies, 125 participants), BOP (MD 4.98%, 95% CI -2.51 to 12.46; 3 studies, 127 participants), CAL (MD 0.07 mm, 95% CI -0.26 to 0.40; 2 studies, 85 participants) and REC (MD -0.20 mm, 95% CI -0.48 to 0.08; 1 study, 24 participants); very low-certainty evidence. These findings were all imprecise and included no clinically important benefits for aPDT. Three studies (134 participants) reported adverse effects: a single participant developed an abscess, though it is not evident whether this was related to aPDT, and two studies observed no adverse effects related to aPDT (moderate-certainty evidence). No studies reported pocket closure at six months, participant satisfaction or quality of life.

AUTHORS' CONCLUSIONS

Because the certainty of the evidence is very low, we cannot be sure if adjunctive aPDT leads to improved clinical outcomes during the active or supportive treatment of periodontitis; moreover, results suggest that any improvements may be too small to be clinically important. The certainty of this evidence can only be increased by the inclusion of large, well-conducted RCTs that are appropriately analysed to account for change in outcome over time or within-participant split-mouth study designs (or both). We found no studies including people with peri-implantitis, and only one study including people with peri-implant mucositis, but this very small study reported no data at six months, warranting more evidence for adjunctive aPDT in this population group.

Decrease of ESKAPE virulence with a cationic heme-mimetic gallium porphyrin photosensitizer: The Trojan horse strategy that could help address antimicrobial resistance

INTRODUCTION

Emerging antibiotic resistance among bacterial pathogens has forced an urgent need for alternative non-antibiotic strategies development that could combat drug resistant-associated infections. Suppression of virulence of ESKAPE pathogens' by targeting multiple virulence traits provides a promising approach.

OBJECTIVES

Here we propose an iron-blocking antibacterial therapy based on a cationic heme-mimetic gallium porphyrin (GaCHP), which antibacterial efficacy could be further enhanced by photodynamic inactivation.

METHODS

We used gallium heme mimetic porphyrin (GaCHP) excited with light to significantly reduce microbial viability and suppress both the expression and biological activity of several virulence traits of both Gram-positive and Gram-negative ESKAPE representatives, i.e., S. aureus and P. aeruginosa. Moreover, further improvement of the proposed strategy by combining it with routinely used antimicrobials to resensitize the microbes to antibiotics and provide enhanced bactericidal efficacy was investigated.

RESULTS

The proposed strategy led to substantial inactivation of critical priority pathogens and has been evidenced to suppress the expression and biological activity of multiple virulence factors in S. aureus and P. aeruginosa. Finally, the combination of GaCHP phototreatment and antibiotics resulted in promising strategy to overcome antibiotic resistance of the studied microbes and to enhance disinfection of drug resistant pathogens.

CONCLUSION

Lastly, considering high safety aspects of the proposed treatment toward host cells, i.e., lack of mutagenicity, no dark toxicity and mild phototoxicity, we describe an efficient alternative that simultaneously suppresses the functionality of multiple virulence factors in ESKAPE pathogens.

Application of Different Wavelengths of LED Lights in Antimicrobial Photodynamic Therapy for the Treatment of Periodontal Disease

Therapeutic light has been increasingly used in clinical dentistry for surgical ablation, disinfection, bio-stimulation, reduction in inflammation, and promotion of wound healing. Photodynamic therapy (PDT), a type of phototherapy, has been used to selectively destroy tumor cells. Antimicrobial PDT (a-PDT) is used to inactivate causative bacteria in infectious oral diseases, such as periodontitis. Several studies have reported that this minimally invasive technique has favorable therapeutic outcomes with a low probability of adverse effects. PDT is based on the photochemical reaction between light, a photosensitizer, and oxygen, which affects its efficacy. Low-power lasers have been predominantly used in phototherapy for periodontal treatments, while light-emitting diodes (LEDs) have received considerable attention as a novel light source in recent years. LEDs can emit broad wavelengths of light, from infrared to ultraviolet, and the lower directivity of LED light appears to be suitable for plaque control over large and complex surfaces. In addition, LED devices are small, lightweight, and less expensive than lasers. Although limited evidence exists on LED-based a-PDT for periodontitis, a-PDT using red or blue LED light could be effective in attenuating bacteria associated with periodontal diseases. LEDs have the potential to provide a new direction for light therapy in periodontics.

A modular phage vector platform for targeted photodynamic therapy of Gram-negative bacterial pathogens

Growing antibiotic resistance has encouraged the revival of phage-inspired antimicrobial approaches. On the other hand, photodynamic therapy (PDT) is considered a very promising research domain for the protection against infectious diseases. Yet, very few efforts have been made to combine the advantages of both approaches in a modular, retargetable platform. Here, we foster the M13 bacteriophage as a multifunctional scaffold, enabling the selective photodynamic killing of bacteria. We took advantage of the well-defined molecular biology of M13 to functionalize its capsid with hundreds of photo-activable Rose Bengal sensitizers and contemporarily target this light-triggerable nanobot to specific bacterial species by phage display of peptide targeting moieties fused to the minor coat protein pIII of the phage. Upon light irradiation of the specimen, the targeted killing of diverse Gram(-) pathogens occurred at subnanomolar concentrations of the phage vector. Our findings contribute to the development of antimicrobials based on targeted and triggerable phage-based nanobiotherapeutics.

Therapeutic contact lenses for the treatment of corneal and ocular surface diseases: advances in extended and targeted drug delivery

The eye is one of the most important organs in the human body providing critical information on the environment. Many corneal diseases can lead to vision loss affecting the lives of people around the world. Ophthalmic drug delivery has always been a major challenge in the medical sciences. Since traditional methods are less efficient (∼ 5%) at delivering drugs to ocular tissues, contact lenses have generated growing interest in ocular drug delivery due to their potential to enhance drug bioavailability in ocular tissues. The main techniques used to achieve sustained release are discussed in this review, including soaking in drug solutions, incorporating drug into multilayered contact lenses, use of vitamin E barriers, molecular imprinting, nanoparticles, micelles and liposomes. The most clinically relevant results on different eye pathologies are presented. In addition, this review summarizes the benefits of contact lenses over eye drops, strategies for incorporating drugs into lenses to achieve sustained release, results of in vitro and in vivo studies, and the recent advances in the commercialization of therapeutic contact lenses for allergic conjunctivitis.

Efficacy of the combination of P5 peptide and photodynamic therapy mediated by bixin and chlorin-e6 against Cutibacterium acnes biofilm

In this study, the action of antimicrobial peptide (AMP) P5 and antimicrobial photodynamic therapy (aPDT) mediated by bixin and chlorin-e6 (Ce6) on Cutibacterium acnes (C. acnes) in planktonic phase and biofilm were evaluated both as monotherapies and combined therapies. Microbial viability after treatments were quantified by colony-forming units per milliliter of the sample (CFU/mL) and have demonstrated that all treatments employed exerted bactericidal activity, reducing the microbial load by more than 3 log₁₀ CFU/mL, also demonstrating for the first time in the literature the antimicrobial photodynamic effect of bixin that occurs mostly through type I mechanism which was proved by the quantification of superoxide anion production. Bacterial biofilm was completely eliminated only after its exposure to aPDT mediated by this PS, however, Ce6 proved to be a more efficient PS, considering that most of the photodynamic effect of bixin- aPDT was exerted by excitation of the endogenous C porphyrins of C. acnes with blue light. The combination of P5 with Ce6-aPDT showed a synergistic effect on the bacterial biofilm with a reduction in microbial load by more than 10 log₁₀ CFU/mL, in which the ability of P5 to permeabilize the polymeric extracellular matrix of the biofilm explains the obtained results, with greater internalization of the PS as shown by the Confocal Laser Scanning Microscopy. One-way ANOVA (Analysis of Variance) with Tukey's post-test and two-way ANOVA with Bonferroni's post-test were used to compare the values of continuous variables between the control group and the treatment groups.

New tendencies in non-surgical periodontal therapy

The aim of this review was to update the evidence of new approaches to non-surgical therapy (NSPT) in the treatment of periodontitis. Preclinical and clinical studies addressing the benefits of adjunctive antimicrobial photodynamic therapy, probiotics, prebiotics/synbiotics, statins, pro-resolving mediators, omega-6 and -3, ozone, and epigenetic therapy were scrutinized and discussed. Currently, the outcomes of these nine new approaches, when compared with subgingival debridement alone, did not demonstrate a significant added clinical benefit. However, some of these new alternative interventions may have the potential to improve the outcomes of NSPT alone. Future evidence based on randomized controlled clinical trials would help clinicians and patients in the selection of different adjunctive therapies.

Antimicrobial and antimycotic photodynamic therapy (review of literature)

This review highlights the possibilities of photodynamic therapy (PDT) using drugs based on chlorin e6, aluminum phthalocyanine, methylene blue as photosensitizers for bacterial and fungal pathologies. This method was developed initially to treat tumor diseases, where it had shown its high efficiency and safety. Now photodynamic therapy is actively used in the treatment of cancers of the skin, bronchi, stomach, cervix, larynx, or other regions. However, numerous studies have been carried out for the entire existence of the method, demonstrating new possibilities of its application. This review highlights a number of studies in which the efficacy and safety of antimicrobial and antimycotic PDT were studied in vivo and in vitro. It has been proven to have a positive effect on the reparative processes in the wound. An experimental study was carried out to study the effectiveness of photodynamic therapy in the treatment of peritonitis in mice. Demonstrated anti-inflammatory potential in the treatment of autoimmune diseases.

Microbiologic Profiles of Patients with Dental Prosthetic Treatment and Periodontitis before and after Photoactivation Therapy-Randomized Clinical Trial

Fixed prosthodontic dental restorations can potentially affect the periodontal tissues and vice versa, the periodontium can influence the longevity and esthetic appearance of dental restorations. We proposed an investigation on total bacterial load, specific periodontal pathogens, and periodontal clinical parameters in patients with dental fixed prosthesis and different degrees of periodontal tissue loss that followed photoactivation therapy (PDT) adjunctive to scaling and root planing. The study was conducted on 160 subjects, which were randomly assigned to scaling and root planing (SRP) alone (52 subjects, 256 sites), SRP and chlorhexidine rinsing (58 subjects, 276 sites), and SRP plus PDT (50 subjects, 318 sites). Periodontal parameters (plaque index, bleeding on probing, probing depth, and clinical attachment loss), followed by total bacterial load and specific periodontal pathogens (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola) were examined in each patient at baseline, one and six months after. PDT exerted significant improvements both in clinical and microbiological load after one month, and these results were maintained 6 months after when compared to chlorhexidine rinsing or SRP alone, especially in severe periodontitis cases. Photoactivation therapy as an adjunctive periodontal therapeutic method was efficient in offering supplementary periodontal improvements in the clinical and microbiological parameters of patients with fixed dental prosthesis, particularly in severe periodontitis cases.

Effects of Antimicrobial Photodynamic Therapy on Organic Solution and Root Surface In Vitro

Antimicrobial photodynamic therapy (a-PDT) is attracting attention as a new form of dental treatment. While it is primarily applied to produce an antibacterial effect, it decreases lipopolysaccharide (LPS) and protease activity. Here, we evaluated differences in the antibacterial activity of a-PDT on three types of bacteria and the effects on the organic substances (i.e., albumin and LPS). Furthermore, we investigated the effects of a-PDT on root surfaces. A FotoSan630® and toluidine blue were used to perform a-PDT in this study. We measured its antimicrobial activity against Porphyromonas gingivalis, Streptococcus mutans, and Enterococcus faecalis. Antimicrobial testing revealed strong antimicrobial action and P. gingivalis, E. faecalis, and S. mutans were almost undetectable after 50, 120, and 100 s, respectively. In organic resolution tests, albumin was significantly decreased from 1 min after a-PDT application onward, while LPS significantly decreased at 5 min after the application. The root surfaces after a-PDT were confirmed to be cleaner than the controls without suffering any damage. Depending on the bacterial species, a-PDT exhibited antimicrobial activity against various types of bacteria and sensitivity differed. Moreover, we reported that a-PDT resolves protein and LPS, enabling the formation of a healthy root surface without any damage.

Inactivation Effect of Violet and Blue Light on ESKAPE Pathogens and Closely Related Non-pathogenic Bacterial Species - A Promising Tool Against Antibiotic-Sensitive and Antibiotic-Resistant Microorganisms

Due to the globally observed increase in antibiotic resistance of bacterial pathogens and the simultaneous decline in new antibiotic developments, the need for alternative inactivation approaches is growing. This is especially true for the treatment of infections with the problematic ESKAPE pathogens, which include Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species, and often exhibit multiple antibiotic resistances. Irradiation with visible light from the violet and blue spectral range is an inactivation approach that does not require any additional supplements. Multiple bacterial and fungal species were demonstrated to be sensitive to this disinfection technique. In the present study, pathogenic ESKAPE organisms and non-pathogenic relatives are irradiated with visible blue and violet light with wavelengths of 450 and 405 nm, respectively. The irradiation experiments are performed at 37°C to test a potential application for medical treatment. For all investigated microorganisms and both wavelengths, a decrease in colony forming units is observed with increasing irradiation dose, although there are differences between the examined bacterial species. A pronounced difference can be observed between Acinetobacter, which prove to be particularly light sensitive, and enterococci, which need higher irradiation doses for inactivation. Differences between pathogenic and non-pathogenic bacteria of one genus are comparatively small, with the tendency of non-pathogenic representatives being less susceptible. Visible light irradiation is therefore a promising approach to inactivate ESKAPE pathogens with future fields of application in prevention and therapy.

Applications of Lasers in Refractory Periodontitis: A Narrative Review

OBJECTIVE

The purpose of the study is to evaluate the various lasers in dentistry and to investigate if it can be used for treatment of refractory periodontitis.

METHODS

The study followed partially the PRISMA guidelines as it is a narrative review. A number of articles were selected from a period of 1980 to 2020 from databases, PubMed, PubMed central, Cochrane and Scopus. Articles related to the effects of lasers on periodontitis both refractory and aggressive were investigated.

RESULTS

After reviewing the literature, 70 articles were found, related to application of lasers in periodontal diseases. Out of the 70, 11 articles pertained to the effect of laser for the treatment of Refractory and inflammatory periodontitis. 5 articles related to experimental animal models, one pertaining to in-vitro and six studies related to in-vivo in human cohorts.

DISCUSSION

It was found that lasers if used in controlled parameters by incorporating laser assisted treatment such as Photodynamic therapy and low level laser therapy can be of use as an adjunct therapy for treatment of refractory periodontitis. The use of different wavelengths in the initial and maintenance phase of periodontal disease plays a positive role. The presence of in-vitro and animal model studies is one of the limitation to this study. The available studies have shown marked reduction in inflammation and better clinical and microbiological parameters. The drawback of this study is the limited literature involving laser management for refractory periodontitis in human cohorts.

CONCLUSION

Different wavelengths of laser and choice of laser assisted periodontal treatment plays an important role in the overall progress and prognosis of periodontal disease activity.

Antimicrobial Photodynamic Therapy in the Control of COVID-19

Antimicrobial photodynamic therapy (aPDT), using well known, safe and cost-effective photosensitizers, such as phenothiazines, e.g., methylene blue (MB), or porphyrins, e.g., protoporphyrin-IX (PP-IX), might help to mitigate the COVID-19 either to prevent infections or to develop photoactive fabrics (e.g., masks, suits, gloves) to disinfect surfaces, air and wastewater, under artificial light and/or natural sunlight.

Comparison between Antimicrobial Photodynamic Therapy and Low-level laser therapy on non-surgical periodontal treatment: A Clinical Study

BACKGROUND

Alternative antibacterial therapeutic modalities, such as antimicrobial photodynamic therapy (aPDT) and low-level laser therapy (LLLT), have been proposed to improve the effectiveness of periodontal treatment. However, clinical studies evaluating the efficiency of these treatments have been inconclusive, partly due to contradictory results regarding their clinical and microbiological effects. The aim of this study was to evaluate the clinical effects of aPDT and LLLT after a one-stage full-mouth disinfection (OSFMD) protocol during periodontitis treatment.

METHODS

A split-mouth clinical trial was conducted in 20 patients presenting at least two contralateral teeth with a probing pocket depth (PD) ≥ 5 mm and bleeding on probing (BOP) on both sides of the mouth. All patients were submitted to an OSFMD protocol. The selected sites randomly received either (1) aPDT (methylene blue as a photosensitizer activated by red and infrared diode laser) or (2) LLLT (red and infrared diode laser). Clinical parameters were assessed at baseline and at 4 and 12 weeks post-treatment.

RESULTS

Both treatment protocols promoted significant reductions in PD, number of deep pockets and BOP and an increase in clinical attachment level (CAL) after 4 and 12 weeks, but there were no differences between the two groups. There was no change in the gingival level (GL) of either group for all periods of analysis. A decrease in the number of moderate pockets (4-5 mm) was found in the LLLT group (5.15 ± 4.20) when compared to the aPDT group (7.10 ± 5.24), but only after 4 weeks.

CONCLUSIONS

In conclusion, both the aPDT and LLLT therapies promoted improvements in periodontal clinical parameters after the OSFMD protocol; however, in general, there were no distinct differences between the two treatment modalities evaluated in this study.

Commercial Local Pharmacotherapeutics and Adjunctive Agents for Nonsurgical Treatment of Periodontitis: A Contemporary Review of Clinical Efficacies and Challenges

Periodontal infections tend to be site-specific, mostly confined to the periodontal pocket. With the surge of antibiotic-resistant bacteria, the trend is shifting towards other therapeutic modalities, especially locally delivered approaches that include other pharmacotherapeutic drugs and medical devices. This narrative review aimed to provide insights into the clinical efficacy of local drug delivery and adjunctive agents used in nonsurgical management of periodontitis. Electronic (PubMed/MEDLINE, CENTRAL, and EMBASE) and bibliographic searches of past systematic reviews were carried out to identify previous publications on the topic. Only relevant literature and randomized controlled trials published in English were selected. In addition, a literature review was developed based on the selected articles. Experimental drugs or agents were excluded. This review highlights the clinically proven and commercially available therapeutic agents related to the management of periodontal disease with comparisons of their clinical efficacies and challenges. A vast array of commercial local pharmacotherapeutic agents had been clinically tested, but the methodologies and clinical results varied within and between each agent used, causing difficulty in drawing conclusions and providing support to the superiority of one agent over another. Considering the benefit-cost ratio with the modest clinical results, the long-term usefulness of these agents remains debatable.

Sub-lethal antimicrobial photodynamic inactivation affects Pseudomonas aeruginosa PAO1 quorum sensing and cyclic di-GMP regulatory systems

BACKGROUND

Antimicrobial photodynamic inactivation (APDI) is a new therapeutic modality which needs more precision during application due to the possibility of exposure of bacteria to sub-lethal doses (sAPDI). In this study, we aimed to evaluate the effect of sAPDI on Pseudomonas aeruginosa quorum sensing (QS) and c-di-GMP signaling which are important virulence factor regulatory systems.

METHODS

Biofilm formation, pyoverdine, pyocyanin and protease production of P. aeruginosa was evaluated before and after a single sAPDI treatment with 0.8 mM methylene blue (MB) plus 1, 2, and 5-min irradiation with red laser light. Fluorescent lasB, rhlA, pqsA, and cdrA reporters of P. aeruginosa PAO1 and P. aeruginosa ΔmexAB-oprM were treated individually with sAPDI and the regulatory signals were detected. The gene expressions were also assessed after sAPDI using quantitative real-time PCR analysis.

RESULTS

Morphological observations and molecular assessments indicated that sAPDI with 0.8 mM MB along with 2- and 5-min irradiation led to an increase in the expression of the Las QS system and c-di-GMP signaling, while 1 min irradiation revealed dissimilar results (increase in lasB expression and decrease in c-di-GMP levels). Expression of rhlA and pqsA did not change in response to sAPDI. Further, a severe lethal effect of sAPDI was observed in P. aeruginosa ΔmexAB-oprM as compared with the wild type strain, whilst there was no difference in QS and c-di-GMP levels as detected by reporters between treated and untreated samples.

CONCLUSION

The results suggest that sAPDI affects QS and c-di-GMP signaling inP. aeruginosa in a time-dependent manner.

Indocyanine Green-Mediated Photodynamic Therapy Reduces Methicillin-Resistant Staphylococcus aureus Drug Resistance

Methicillin-resistant Staphylococcus aureus (MRSA) skin-wound infections are associated with considerable morbidity and mortality. Indocyanine green (ICG), a safe and inexpensive dye used in clinical imaging, can be activated by near-infrared in photodynamic therapy (PDT) and photothermal therapy (PTT) to effectively kill MRSA. However, how this treatment affects MRSA drug sensitivity remains unknown. The drug-sensitivity phenotypes, bacterial growth rate, and cell-wall thickness of three MRSA strains were analyzed after ICG-PDT. Drug-resistant gene expressions were determined by polymerase chain reaction (PCR) and quantitative reverse transcription (qRT)-PCR. Related protein expressions were examined with immunoblotting. Drug sensitivity was further evaluated in animal models. MRSA that survived the treatment grew faster, and the cell wall became thinner compared to parental cells. These cells became more sensitive to oxacillin, which was partly related to mecA complex gene deletion. Skin necrosis caused by ICG-PDT-treated MRSA infection was smaller and healed faster than that infected with parental cells. With oxacillin therapy, no bacteria could be isolated from mouse lung tissue infected with ICG-PDT-treated MRSA. ICG-PDT drives MRSA toward an oxacillin-sensitive phenotype. It has the potential to develop into an alternative or adjuvant clinical treatment against MRSA wound infections.

Clinical and Biological Effects of Adjunctive Photodynamic Therapy in Refractory Periodontitis

Introduction: To date, no novel treatment approach is available for optimum outcomes regarding refractory periodontitis. The aim of the present study was to assess the efficiency of photodynamic therapy (PDT) in treating patients diagnosed with refractory periodontitis and compare the clinical and biological outcomes of conventional periodontal treatment with or without adjunctive PDT in these patients, by assessing clinical parameters (plaque index [PI], gingival recession [GR], bleeding on probing [BOP], periodontal probing depth [PPD] and clinical attachment level [CAL]) as well as biological parameters (IL-1β) in the gingival crevicular fluid (GCF). Methods: Sixteen patients within the age of 30 to 60 years, with a mean age of 40 years old, diagnosed with refractory periodontitis were included. In this split mouth design study, 2 quads (1 upper + 1 lower) from the same patient were randomly treated with (scaling and root planing [SRP]+PDT) together. The other 2 quadrants (1 upper + 1 lower) were treated by SRP only and selected to serve as controls. Clinical parameters including PI, GR, BOP, PPD and CAL and biological parameters (IL-1β) in the GCF were measured at baseline, then at, 2 and 6 months after therapy. Results: A statistically significant reduction in several clinical parameters as, BOP (P < 0.001), PI (P < 0.001), PPD (P < 0.001) and CAL (P < 0.001) in quadrant treated with SRP and adjunctive PDT when compared to control group treated with SRP alone was observed and both therapies showed non-statistically significant differences in the reduction of IL-1β level. Conclusion: The inclusion of PDT as an adjunctive measure to nonsurgical conventional periodontal treatment seems to be a useful therapeutic measure in refractory periodontitis treatment.

Quorum-sensing-regulated virulence factors in Pseudomonas aeruginosa are affected by sub-lethal photodynamic inactivation

BACKGROUND

Photodynamic inactivation (PDI) is recognized as a new antimicrobial approach. It is likely that in human hosts receiving this therapy, pathogens may encounter sub-lethal doses of PDI (sPDI), which may affect microbial virulence. This study was aimed to evaluate the effect of sPDI using methylene blue (MB) on the expression of genes belonging to two quorum sensing (QS) operons (rhl and las systems) and two genes necessary for pyocyanin and rhamnolipid production (phzM and rhlA) under QS control in Pseudomonas aeruginosa.

METHODS

Ability of pyocyanin and rhamnolipid production of P. aeruginosa ATCC 27853 and clinical isolates exposed to sPDI (MB at 0.012 mM and light dose of 23 J/cm² was evaluated. The effect of sPDI on expression of rhlI, rhlR, lasI, lasR, phzM and rhlA were also evaluated by quantitative real time polymerase chain reaction.

RESULTS

sPDI led to the down-regulation of the expression of all four QS genes (lasI, lasR, rhlI and rhlR) and rhamnolipid gene (rhlA). However, up-regulation of pyocyanin gene (phzM) was observed after sPDI. These results were consistent with phenotypic changes.

CONCLUSION

This study suggests that oxidative stress induced by sPDI can affect QS-regulated virulence factors of P. aeruginosa such as pyocyanin and rhamnolipids in different ways.

Antimicrobial blue light photoinactivation of Pseudomonas aeruginosa: Quorum sensing signaling molecules, biofilm formation and pathogenicity

Pseudomonas aeruginosa is a common causative bacterium of acute and chronic infections that have been responsible for high mortality over the past decade. P. aeruginosa produces many virulence factors such as toxins, enzymes and dyes that are strongly dependent on quorum sensing (QS) signaling systems. P. aeruginosa has three major QS systems (las, rhl and Pseudomonas quinolone signal) that regulate the expression of genes encoding virulence factors as well as biofilm production and maturation. Antimicrobial blue light (aBL) is considered a therapeutic option for bacterial infections and has other benefits, such as reducing bacterial virulence. Therefore, this study investigated the efficacy of aBL to reduce P. aeruginosa pathogenicity. aBL treatment resulted in the reduced activity of certain QS signaling molecules in P. aeruginosa and inhibited biofilm formation. in vivo tests using a Caenorhabditis elegans infection model indicated that sublethal aBL decreased the pathogenicity of P. aeruginosa. aBL may be a new virulence-targeting therapeutic approach.

Clinical effects of photodynamic therapy as an adjunct to full-mouth ultrasonic scaling and root planing in treatment of chronic periodontitis

Background and aims

Photodynamic therapy (PDT) is a potential strategy to eliminate infection in the specific tissue. It uses lower-power laser to activate a photosensitizing agent. Studies have shown the benefit of PDT in the periodontal treatment. The aim of this study was to evaluate the periodontal changes after applying PDT as an adjunct to one visit full-mouth SRP (scaling and root planing) with subgingival piezoelectric ultrasonic scaler compared with full-mouth SRP alone.

Methods

A split-mouth randomized clinical trial was designed. Twenty patients with moderate to severe chronic periodontitis were treated with subgingival piezoelectric ultrasonic device alone in control group and adjunct treated with PDT in the test group. Probing pocket depth (PD), clinical attachment level (CAL), plaque index (PI), gingival bleeding index (GBI) and gingival inflammation index (GI) were evaluated at baseline, 1 month, 3 and 6 months after treatment. Only sites with PD ≥ 4 mm at baseline were calculated.

Results

All periodontal parameters were significantly improved in both groups at 1 month, 3 and 6 months after treatment. All parameters in test group were better than that control group, with statistically significant differences of GBI and GI (P < 0.05) at 3 and 6 months after treatment but no statistically significant differences of PD, CAL and PI.

Conclusions

One visit full-mouth ultrasonic SRP seems to have good enough effort for the periodontal status till 6 months. The adjunct treatment of PDT provided positive effect in term of GBI and GI.

Blue light treatment of Pseudomonas aeruginosa: Strong bactericidal activity, synergism with antibiotics and inactivation of virulence factors

Pseudomonas aeruginosa is among the most common pathogens responsible for both acute and chronic infections of high incidence and severity. Additionally, P. aeruginosa resistance to conventional antimicrobials has increased rapidly over the past decade. Therefore, it is crucial to explore new therapeutic options, particularly options that specifically target the pathogenic mechanisms of this microbe. The ability of a pathogenic bacterium to cause disease is dependent upon the production of agents termed 'virulence factors', and approaches to mitigate these agents have gained increasing attention as new antibacterial strategies. Although blue light irradiation is a promising alternative approach, only limited and preliminary studies have described its effect on virulence factors. The current study aimed to investigate the effects of lethal and sub-lethal doses of blue light treatment (BLT) on P. aeruginosa virulence factors. We analyzed the inhibitory effects of blue light irradiation on the production/activity of several virulence factors. Lethal BLT inhibited the activity of pyocyanin, staphylolysin, pseudolysin and other proteases, but sub-lethal BLT did not affect the production/expression of proteases, phospholipases, and flagella- or type IV pili-associated motility. Moreover, a eukaryotic cytotoxicity test confirmed the decreased toxicity of blue light-treated extracellular P. aeruginosa fractions. Finally, the increased antimicrobial susceptibility of P. aeruginosa treated with sequential doses of sub-lethal BLT was demonstrated with a checkerboard test. Thus, this work provides evidence-based proof of the susceptibility of drug-resistant P. aeruginosa to BLT-mediated killing, accompanied by virulence factor reduction, and describes the synergy between antibiotics and sub-lethal BLT.

Effects of photodynamic therapy in periodontal treatment: A randomized, controlled clinical trial

AIM

To evaluate the effects of photodynamic therapy (PDT) in the nonsurgical treatment of chronic periodontitis.

MATERIALS AND METHODS

A randomized, single-blind, controlled, parallel-group clinical trial was performed. Sixty patients were enrolled: 20 healthy controls and 40 patients with periodontitis. The 40 patients were randomized for scaling and root planing (SRP) or SRP + PDT. Periodontal (plaque index, probing depth, clinical recession, clinical attachment level, bleeding on probing and gingival crevicular fluid volume, corresponding to 381 versus 428 critical sites), microbiological (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Prevotella intermedia and Campylobacter rectus presence, 18 versus 19 samples) and biochemical (interleukin (IL)-1β, IL-6 and tumour necrosis factor (TNF)-α, receptor activator of nuclear factor-kappaB ligand (RANK-L) and osteoprotegerin (OPG) levels, 18 versus 19 samples) parameters were recorded.

RESULTS

Within each group, significant improvements were found for clinical parameters, though without significant differences between groups. RANK-L was significantly decreased at week 13 in the SRP + PDT group compared with the SRP group. SRP + PDT, but not SRP alone, significantly reduced the abundance of A. actinomycetemcomitans.

CONCLUSIONS

Except for a significant decrease in the pathogenic burden of A. actinomycetemcomitans, coadjuvant PDT resulted in no additional improvement compared with SRP alone in patients diagnosed with moderate-to-advanced chronic periodontitis.

Virulence factors of fluconazole-susceptible and fluconazole-resistant Candida albicans after antimicrobial photodynamic therapy

This study evaluated the effects of antimicrobial photodynamic therapy (aPDT) mediated by Photodithazine® (PDZ) and LED light on the virulence factors of fluconazole-susceptible (CaS) and fluconazole-resistant (CaR) Candida albicans. Standardized suspensions of strains were prepared (10⁷), and after 48 h of biofilm formation, these strains were incubated with PDZ (100 mg/L) for 20 min and exposed to LED light (660 nm, 37.5 J/cm²). Additional samples were treated with PDZ or light only, and the control consisted of biofilms that received no treatment. After aPDT, the cells were recovered and the virulence factors were evaluated. To analyze the capacity of adhesion, cells were recovered after aPDT and submitted to the adhesion process in the bottom of a 96-well plate. After this, metabolic activity tests (XTT assay) and cell viability (colony forming units per milliliter, CFU/mL) were applied. To evaluate the biofilm-forming ability after aPDT, the cells recovered were submitted to biofilm formation procedures, and the biofilm formed was evaluated by XTT, CFU/mL, and total biomass (crystal violet) tests. Lastly, the capacity for synthesizing protease and phospholipase enzymes after aPDT was evaluated by fluorimetric tests. Data were analyzed by two- or three-way ANOVA tests (p ≤ 0.05). It was verified that aPDT reduced the viability of both strains, fluconazole-susceptible and fluconazole-resistant C. albicans. It was also observed that the CaR strain had lower susceptibility to the aPDT when compared with the CaS strain. However, regarding the virulence factors evaluated, it was demonstrated that aPDT did not alter the adherence and biofilm formation ability and enzymatic production.

Phototherapeutic spectrum expansion through synergistic effect of mesoporous silica trio-nanohybrids against antibiotic-resistant gram-negative bacterium

The extensive impact of antibiotic resistance has led to the exploration of new anti-bacterial modalities. We designed copper impregnated mesoporous silica nanoparticles (Cu-MSN) with immobilizing silver nanoparticles (SNPs) to apply photodynamic inactivation (PDI) of antibiotic-resistant E. coli. SNPs were decorated over the Cu-MSN surfaces by coordination of silver ions on diamine-functionalized Cu-MSN and further reduced to silver nanoparticles with formalin. We demonstrate that silver is capable of sensitizing the gram-negative bacteria E. coli to a gram-positive specific phototherapeutic agent in vitro; thereby expanding curcumin's phototherapeutic spectrum. The mesoporous structure of Cu-MSN remains intact after the exterior decoration with silver nanoparticles and subsequent curcumin loading through an enhanced effect from copper metal-curcumin affinity interaction. The synthesis, as well as successful assembly of the functional nanomaterials, was confirmed by various physical characterization techniques. Curcumin is capable of producing high amounts of reactive oxygen species (ROS) under light irradiation, which can further improve the silver ion release kinetics for antibacterial activity. In addition, the positive charged modified surfaces of Cu-MSN facilitate antimicrobial response through electrostatic attractions towards negatively charged bacterial cell membranes. The antibacterial action of the synthesized nanocomposites can be activated through a synergistic mechanism of energy transfer of the absorbed light from SNP to curcumin.

Photoantimicrobials-are we afraid of the light?

Although conventional antimicrobial drugs have been viewed as miraculous cure-alls for the past 80 years, increasing antimicrobial drug resistance requires a major and rapid intervention. However, the development of novel but still conventional systemic antimicrobial agents, having only a single mode or site of action, will not alleviate the situation because it is probably only a matter of time until any such agents will also become ineffective. To continue to produce new agents based on this notion is unacceptable, and there is an increasing need for alternative approaches to the problem. By contrast, light-activated molecules called photoantimicrobials act locally via the in-situ production of highly reactive oxygen species, which simultaneously attack various biomolecular sites in the pathogenic target and therefore offer both multiple and variable sites of action. This non-specificity at the target circumvents conventional mechanisms of resistance and inhibits the development of resistance to the agents themselves. Photoantimicrobial therapy is safe and easy to implement and, unlike conventional agents, the activity spectrum of photoantimicrobials covers bacteria, fungi, viruses, and protozoa. However, clinical trials of these new, truly broad-spectrum, and minimally toxic agents have been few, and the funding for research and development is almost non-existent. Photoantimicrobials constitute one of the few ways forward through the morass of drug-resistant infectious disease and should be fully explored. In this Personal View, we raise awareness of the novel photoantimicrobial technologies that offer a viable alternative to conventional drugs in many relevant application fields, and could thus slow the pace of resistance development.

Effect of Combined Therapy Using Diode Laser and Photodynamic Therapy on Levels of IL-17 in Gingival Crevicular Fluid in Patients With Chronic Periodontitis

Introduction: The aim of this study was to evaluate the efficacy of combination therapy of diode laser and photodynamic therapy (PDT) as an adjunct to scaling and root planing (SRP) on interleukin-17 (IL-17) levels in gingival crevicular fluid (GCF) in patients with chronic periodontitis. Methods: Thirty subjects with chronic periodontitis were included. All teeth received periodontal treatment comprising of SRP. Using a split mouth study design, the test group was additionally treated with a combination therapy of diode laser and PDT. GCF was collected to evaluate IL-17 levels at baseline and 3 months. Results: There was no difference in baseline values for levels of IL-17 in GCF in the test group and the control group. A significant decrease in GCF levels of IL-17 was observed in both treatment groups 3 months after treatment (P < 0.001). However, the treatment groups showed no significant difference (P > 0.05). Conclusion: Based on the results of the present study it was concluded that, GCF levels of IL-17 changed significantly after treatment regardless of treatment modality.

Extracellular Bacterial Proteases in Chronic Wounds: A Potential Therapeutic Target?

Significance: Bacterial biofilms are considered to be responsible for over 80% of persistent infections, including chronic lung infections, osteomyelitis, periodontitis, endocarditis, and chronic wounds. Over 60% of chronic wounds are colonized with bacteria that reside within a biofilm. The exaggerated proteolytic environment of chronic wounds, more specifically elevated matrix metalloproteinases, is thought to be one of the possible reasons as to why chronic wounds fail to heal. However, the role of bacterial proteases within chronic wounds is not fully understood. Recent Advances: Recent research has shown that bacterial proteases can enable colonization and facilitate bacterial immune evasion. The inhibition of bacterial proteases such as Pseudomonas aeruginosa elastase B (LasB) has resulted in the disruption of the bacterial biofilm in vitro. P. aeruginosa is thought to be a key pathogen in chronic wound infection, and therefore, the disruption of these biofilms, potentially through the targeting of P. aeruginosa bacterial proteases, is an attractive therapeutic endeavor. Critical Issues: Disrupting biofilm formation through the inhibition of bacterial proteases may lead to the dissemination of bacteria from the biofilm, allowing planktonic cells to colonize new sites within the wound. Future Directions: Despite a plethora of evidence supporting the role of bacterial proteases as virulence factors in infection, there remains a distinct lack of research into the effect of bacterial proteases in chronic wounds. To assess the viability of targeting bacterial proteases, future research should aim to understand the role of these proteases in a variety of chronic wound subtypes.

Efficacy of scaling and root planing with and without adjunct antimicrobial photodynamic therapy on the expression of cytokines in the gingival crevicular fluid of patients with periodontitis: A systematic review

BACKGROUND

The aim of the present review was to study the efficacy of scaling and root planing (SRP) with and without adjunct antibacterial photodynamic therapy (aPDT) on the expression of cytokines in the gingival crevicular fluid (GCF) of patients with periodontitis.

METHODS

In order to address the focused question: "What is the efficacy of SRP with and without aPDT on the expression of cytokines in the GCF of patients with periodontitis" an electronic search without time or language restrictions was conducted up to and including July 2016 in indexed databases using various key words. The exclusion criteria included reviews, laboratory and experimental studies, case reports, commentaries, letters to the editor, interviews, updates, studies where intervention group received aPDT without previous SRP, and studies where local delivery of antibiotics was used as adjunctive therapy to aPDT.

RESULTS

Six randomized control trials were included in the present systematic review. All studies included a control group which received only SRP. Results from 34% of studies reported lower cytokine levels among individuals receiving adjunct aPDT to SPT compared to patients receiving SRP alone. Selective cytokines reduction in the GCF following SRP with adjunct aPDT compared with SRP alone was reported in 50% of the studies. In one study SRP with adjunct aPDT failed to reduce GCF cytokine concentration.

CONCLUSION

From the literature reviewed the efficacy aPDT as adjunct to SRP in downregulating GCF cytokines remains debatable. Further well-designed studies are needed in this regard.

A Perspective on the Trends and Challenges Facing Porphyrin-Based Anti-Microbial Materials

The emergence of multidrug resistant bacterium threatens to unravel global healthcare systems, built up over centuries of medical research and development. Current antibiotics have little resistance against this onslaught as bacterium strains can quickly evolve effective defense mechanisms. Fortunately, alternative therapies exist and, at the forefront of research lays the photodynamic inhibition approach mediated by porphyrin based photosensitizers. This review will focus on the development of various porphyrins compounds and their incorporation as small molecules, into polymers, fibers and thin films as practical therapeutic agents, utilizing photodynamic therapy to inhibit a wide spectrum of bacterium. The use of photodynamic therapy of these porphyrin molecules are discussed and evaluated according to their electronic and bulk material effect on different bacterium strains. This review also provides an insight into the general direction and challenges facing porphyrins and derivatives as full-fledged therapeutic agents and what needs to be further done in order to be bestowed their rightful and equal status in modern medicine, similar to the very first antibiotic; penicillin itself. It is hoped that, with this perspective, new paradigms and strategies in the application of porphyrins and derivatives will progressively flourish and lead to advances against disease.

Sub-lethal doses of photodynamic therapy affect biofilm formation ability and metabolic activity of Enterococcus faecalis

BACKGROUND

During photodynamic therapy (PDT) in the treatment of a primary endodontic infection, it is extremely likely that microorganisms would be exposed to sub-lethal doses of PDT (sPDT). Although sPDT cannot kill microorganisms, it can considerably influence microbial virulence. This study was conducted to characterize the effect of sPDT using toluidine blue O (TBO), methylene blue (MB), and indocyanine green (ICG) on biofilm formation ability and metabolic activity of Enterococcus faecalis.

METHODS

The antimetabolic and antibiofilm potential of ICG-, TBO-, and MB-sPDT against E. faecalis was analyzed at sub-lethal doses (1/2-1/64 minimum inhibitory concentration) using the XTT reduction assay, crystal violet assay, and scanning electron microscopy.

RESULTS

Higher doses of sPDT adversely affected biofilm formation ability and metabolic activity. ICG-, TBO-, and MB-PDT at a maximum sub-lethal dose markedly reduced the formation of biofilm up to 42.8%, 22.6%, and 19.5%, respectively. ICG-, TBO-, and MB-sPDT showed a marked reduction in bacterial metabolic activity by 98%, 94%, and 82%, respectively. ICG-PDT showed a stronger inhibitory effect on biofilm formation in E. faecalis than MB- and TBO-PDT at sub-lethal levels. Interestingly, a gradual increase in metabolic activity and biofilm formation upon exposure to a lower dose of test sPDT were observed.

CONCLUSION

sPDT showed dual effect on biofilm formation ability and metabolic activity of E. faecalis. High doses revealed antimetabolic and antibiofilm potential activity, whereas lower doses had conflicting results. Hence, when PDT is prescribed in clinical settings, the dose of PDT used in vivo should be taken into consideration.

Bacterial imaging and photodynamic inactivation using zinc(II)-dipicolylamine BODIPY conjugates

Targeted imaging and antimicrobial photodynamic inactivation (PDI) are emerging methods for detecting and eradicating pathogenic microorganisms. This study describes two structurally related optical probes that are conjugates of a zinc(II)-dipicolylamine targeting unit and a BODIPY chromophore. One probe is a microbial targeted fluorescent imaging agent, mSeek, and the other is an oxygen photosensitizing analogue, mDestroy. The conjugates exhibited high fluorescence quantum yield and singlet oxygen production, respectively. Fluorescence imaging and detection studies examined four bacterial strains: E. coli, S. aureus, K. pneumonia, and B. thuringiensis vegetative cells and purified spores. The fluorescent probe, mSeek, is not phototoxic and enabled detection of all tested bacteria at concentrations of ∼100 CFU mL(-1) for B. thuringiensis spores, ∼1000 CFU mL(-1) for S. aureus and ∼10,000 CFU mL(-1) for E. coli. The photosensitizer analogue, mDestroy, inactivated 99-99.99% of bacterial samples and selectively killed bacterial cells in the presence of mammalian cells. However, mDestroy was ineffective against B. thuringiensis spores. Together, the results demonstrate a new two-probe strategy to optimize PDI of bacterial infection/contamination.

Effect of Photodynamic Therapy on the Virulence Factors of Staphylococcus aureus

Staphylococcus aureus is a Gram-positive bacterium that is present in the human microbiota. Nevertheless, these bacteria can be pathogenic to the humans. Due to the increasing occurrence of antibiotic-resistant S. aureus strains, new approaches to control this pathogen are necessary. The antimicrobial photodynamic inactivation (PDI) process is based in the combined use of light, oxygen, and an intermediary agent (a photosensitizer). These three components interact to generate cytotoxic reactive oxygen species that irreversibly damage vital constituents of the microbial cells and ultimately lead to cell death. Although PDI is being shown to be a promising alternative to the antibiotic approach for the inactivation of pathogenic microorganisms, information on effects of photosensitization on particular virulence factors is strikingly scarce. The objective of this work was to evaluate the effect of PDI on virulence factors of S. aureus and to assess the potential development of resistance of this bacterium as well as the recovery of the expression of the virulence factors after successive PDI cycles. For this, the photosensitizer 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin tetra-iodide (Tetra-Py⁺-Me) and six strains of S. aureus [one reference strain, one strain with one enterotoxin, two strains with three enterotoxins and two methicillin resistant strains (MRSA) – one with five enterotoxins and the other without enterotoxins] were used. The effect of photosensitization on catalase activity, beta hemolysis, lipases, thermonuclease, enterotoxins, coagulase production, and resistance/susceptibility to methicillin was tested. To assess the development of resistance after successive cycles of treatment, three strains of S. aureus (ATCC 6538, 2065 MA, and SA 3 MRSA) were used. The surviving colonies of a first cycle of PDI were collected from the solid medium and subjected to further nine consecutive cycles of PDI. The results indicate that the expression of some external virulence factors is affected by PDI and enterotoxin producing strains were more susceptible to PDI than non-toxigenic strains. The surviving bacteria did not develop resistance. PDI, contrarily to traditional antibiotics, inhibited the expression of virulence factors, efficiently inactivating either highly virulent strains and low virulent S. aureus strains, inactivating also antibiotic susceptible and resistant strains, without development of photoresistance after at least 10 consecutive cycles of treatment, and so this therapy may become a strong promising alternative to antibiotics to control pathogenic microorganisms.

Enhancement of photodynamic inactivation against Pseudomonas aeruginosa by a nano-carrier approach

As pathogens steadily develop resistance to widely used antibiotics, new methodologies for their efficient inactivation must be developed. Photodynamic therapy is an upcoming technique that provides an alternative option for treating pathogenic infections. The efficiency of photodynamic therapy has been limited by the use of aqueous mediums for dispersing photosensitising agents. Toluidine Blue O (TBO) was chosen for this study as a cationic photosensitiser to inhibit Gram-negative bacterium Pseudomonas aeruginosa. Enhanced delivery of the photosensitiser was ensured by utilising an essential oil-based microemulsion. The efficiency of photodynamic therapy was further improved by the use of a chemical penetration enhancer to improve permeability of the bacterial outer membrane. TBO accumulation patterns in neonate pig skin were studied using confocal laser scanning microscopy. The physicochemical properties of the TBO loaded microemulsion, including UV-vis absorbance, size distribution and zeta potential, were analysed to understand the enhanced antimicrobial activity. Confocal laser scanning microscopy confirmed the formation of a TBO reservoir in the skin by the TBO-loaded microemulsions. TBO (5 μg/mL) in the vehicles significantly inhibited the growth of P. aeruginosa. All these efforts resulted in inhibition obtained at a drug concentration and light intensity much lower than what is reported by the works of previous investigators.

Modulation of inflammatory response of wounds by antimicrobial photodynamic therapy

BACKGROUND AND AIMS

Management of infections caused by Pseudomonas aeruginosa is becoming difficult due to the rapid emergence of multi-antibiotic resistant strains. Antimicrobial photodynamic therapy (APDT) has a lot of potential as an alternative approach for inactivation of antibiotic resistant bacteria. In this study we report results of our investigations on the effect of poly-L-lysine conjugate of chlorine p6 (pl-cp6) mediated APDT on the healing of P.aeruginosa infected wounds and the role of Nuclear Factor kappa B (NF-kB) induced inflammatory response in this process.

MATERIALS AND METHOD

Excisional wounds created in Swiss albino mice were infected with ∼10(7) colony forming units of P.aeruginosa. Mice with wounds were divided into three groups: 1) Uninfected, 2) Infected, untreated control (no light, no pl-cp6), 3) Infected, APDT. After 24 h of infection (day 1 post wounding), the wounds were subjected to APDT [pl-cp6 applied topically and exposed to red light (660 ± 25 nm) fluence of ∼ 60 J/cm(2)]. Subsequent to APDT, on day 2 and 5 post wounding (p.w), measurements were made on biochemical parameters of inflammation [toll like receptor-4 (TLR-4), NF-kB, Inteleukin (IL)-[1α, IL-β, and IL-2)] and cell proliferation [(fibroblast growth factor-2 (FGF-2), alkaline phosphatase (ALP)].

RESULTS

In comparison with untreated control, while expression of TLR-4, NF-kB (p105 and p50), and proinflammatory interleukins (IL-1α, IL-1β,IL-2) were reduced in the infected wounds subjected to APDT, the levels of FGF-2 and ALP increased, on day 5 p.w.

CONCLUSION

The measurements made on the inflammatory markers and cell proliferation markers suggest that APDT reduces inflammation caused by P.aeruginosa and promotes cell proliferation in wounds.

Drug Carrier for Photodynamic Cancer Therapy

Photodynamic therapy (PDT) is a non-invasive combinatorial therapeutic modality using light, photosensitizer (PS), and oxygen used for the treatment of cancer and other diseases. When PSs in cells are exposed to specific wavelengths of light, they are transformed from the singlet ground state (S₀) to an excited singlet state (S₁-Sn), followed by intersystem crossing to an excited triplet state (T₁). The energy transferred from T₁ to biological substrates and molecular oxygen, via type I and II reactions, generates reactive oxygen species, (¹O₂, H₂O₂, O₂*, HO*), which causes cellular damage that leads to tumor cell death through necrosis or apoptosis. The solubility, selectivity, and targeting of photosensitizers are important factors that must be considered in PDT. Nano-formulating PSs with organic and inorganic nanoparticles poses as potential strategy to satisfy the requirements of an ideal PDT system. In this review, we summarize several organic and inorganic PS carriers that have been studied to enhance the efficacy of photodynamic therapy against cancer.