ALA-PDT combined with antibiotics for the treatment of atypical mycobacterial skin infections: Outcomes and safety

ALA-PDT shortens the course of antibiotic therapy for skin infection caused by Mycobacterium marinum

BACKGROUND

Recently, the number of cases of Mycobacterium marinum infection has increased. Due to the nonspecific clinical manifestations and lack of standardized treatment guidelines, these infections are often misdiagnosed and are challenging to treat.

METHODS

In this study, four patients had M. marinum skin infections accompanied by a high-risk exposure history and were diagnosed by bacterial culture and gene chip. Two patients were treated with antibiotic therapy alone, and the other two patients were treated with 5-aminolevulinic acid photodynamic therapy (ALA-PDT) combined with antibiotics.

RESULTS

All four patients enrolled in the study were cured with 100 % efficacy. Two patients were cured after receiving two active antibiotics for 4 months. The other two patients, having considered the drug resistance and intolerance described above, were cured after receiving two active antibiotics for 1-1.5 months along with combination therapy with ALA-PDT.

CONCLUSION

Combination therapy with ALA-PDT and antibiotics was chosen to shorten the duration of antibiotic treatment and reduce the occurrence of adverse reactions.

Photodynamic therapy: a new approach to the treatment of Nontuberculous Mycobacterial skin and soft tissue infections

Nontuberculous mycobacterial skin and soft tissue infections are rising and are causing social concern due to the growth of cosmetic dermatology and immune-compromised populations. For the treatment of nontuberculous mycobacteria, several novel strategies have been investigated. One of them, photodynamic therapy, is a recently developed therapeutic strategy that has shown promise in managing nontuberculous mycobacterial skin and soft tissue infections. In this review, we first present an overview of the current status of the therapy and then summarize and analyze the cases of photodynamic therapy used to treat nontuberculous mycobacterial skin and soft tissue infections. We also discussed the feasibility of photodynamic therapy for treating nontuberculous mycobacterial skin soft tissue infections and the related mechanisms, providing a potential new option for clinical treatment.

Using mixed reality technique combines multimodal imaging signatures to adjuvant glioma photodynamic therapy

Background

Photodynamic therapy (PDT) promotes significant tumor regression and extends the lifetime of patients. The actual operation of PDT often relies on the subjective judgment of experienced neurosurgeons. Patients can benefit more from precisely targeting PDT's key operating zones.

Methods

We used magnetic resonance imaging scans and created 3D digital models of patient anatomy. Multiple images are aligned and merged in STL format. Neurosurgeons use HoloLens to import reconstructions and assist in PDT execution. Also, immunohistochemistry was used to explore the association of hyperperfusion sites in PDT of glioma with patient survival.

Results

We constructed satisfactory 3D visualization of glioma models and accurately localized the hyperperfused areas of the tumor. Tumor tissue taken in these areas was rich in CD31, VEGFA and EGFR that were associated with poor prognosis in glioma patients. We report the first study using MR technology combined with PDT in the treatment of glioma. Based on this model, neurosurgeons can focus PDT on the hyperperfused area of the glioma. A direct benefit was expected for the patients in this treatment.

Conclusion

Using the Mixed Reality technique combines multimodal imaging signatures to adjuvant glioma PDT can better exploit the vascular sealing effect of PDT on glioma.

Combination treatment with antibiotics and photodynamic therapy in refractory mycobacterium marinum infection: A case report

Mycobacterium marinum can cause skin infection. Treatment of this infection often requires a chronic multidrug regimen. For refractory cases with progression, relapse, or slow recovery, long-term medication may cause problems such as ineffectiveness, poor patient compliance, and drug intolerance. We report a refractory case with a total treatment time of 2 years, successfully cured by the combination of antibiotics and photodynamic therapy. Our case shows that combination treatment with antibiotics and photodynamic therapy may be an effective approach for refractory Mycobacterium marinum infection.

Enhancement of the cytotoxic effect of dihydroartemisinin in high-risk human papillomavirus-infected cells by aminolevulinic acid via the Bax/Bcl-2-caspase pathway

BACKGROUND

Traditional treatments for human papillomavirus-related cutaneous diseases include 5-aminolevulinic acid photodynamic therapy, cryotherapy, microwave ablation, and surgical resection. These treatment methods involvevarious adverse reactions; therefore, it remains necessary to explore new treatment methods. Dihydroartemisinin shows cytotoxic effects against several malignancies by producing reactive oxygen species, and heme environments reportedly enhance its activity. However, the underlying mechanismsare still unclear. Therefore, we investigated the mechanism of dihydroartemisininin inhuman papillomavirus-infected cells.

METHODS

HeLa cells were treated with dihydroartemisinin, 5-aminolevulinic acid, and succinylacetone. The cell viability, apoptosis, mitochondrial membrane potential, and reactive oxygen species levels were investigated, and via western blotting analysis and polymerase chain reaction, dihydroartemisinin activity-related pathways were also determined.

RESULTS

Dihydroartemisinin inhibited HeLa cell proliferation and promoted cell apoptosis via the Bax/Bcl-2-Caspase pathway in a concentration-dependent manner. The specific cytotoxicity toward HeLa cells was enhanced by the addition of 5-aminolevulinic acid, a clinically used heme-synthesis precursor, owing to an increase in heme levels. Conversely, following the addition of succinylacetone, a heme synthesis blocker, heme levels decreased. Furthermore, dihydroartemisinin significantly increased reactive oxygen species levels as intracellular heme synthesis increased. Moreover, photodynamic therapy following dihydroartemisinin and 5-aminolevulinic acid treatment further enhanced the cytotoxic effect of dihydroartemisinin on high-risk human papillomavirus-infected cells.

CONCLUSIONS

Dihydroartemisinin exerts acytotoxic effect on high-risk human papillomavirus-infected cells by modulating heme levels via the Bax/Bcl-2-Caspase pathway, and the dihydroartemisinin, 5-aminolevulinic acid, photodynamic therapy combination treatment significantly enhanced its cytotoxic effect on human papillomavirus-infected cells.

Mathematical modelling for antimicrobial photodynamic therapy mediated by 5-aminolaevulinic acid: An in vitro study

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) using aminolaevulinic acid (ALA) is a promising alternative to antibiotic therapy. ALA administration induces protoporphyrin IX (PpIX) accumulation in bacteria, and light excitation of the accumulated PpIX generates singlet oxygen to bacterial toxicity. Several factors, including drug administration and light irradiation conditions, contribute to the antibiotic effect. Such multiple parameters should be determined moderately for effective aPDT in clinical practice.

METHODS

A mathematical model to predict bacterial dynamics in ALA-aPDT following clinical conditions was constructed. Applying a pharmacokineticspharmacodynamics (PK-PD) approach, which is widely used in antimicrobial drug evaluation, viable bacteria count by defining the bactericidal rate as the concentration of singlet oxygen produced when PpIX in bacteria is irradiated by light.

RESULTS

The in vitro experimental results of ALA-aPDT for Pseudomonas aeruginosa demonstrated the PK-PD model validity. The killing rate has an upper limit, and the lower power density for a long irradiation time can suppress the viable bacteria number when the light dosages are the same.

CONCLUSIONS

This study proposed a model of bacterial viability change in ALA-aPDT based on the PK-PD model and confirmed, by in vitro experiments using PA, that the variation of bacterial viability with light-sensitive substance concentration and light irradiation power densities could be expressed. Further validation of the PK-PD model with other gram negative and gram positive strains will be needed.

Dramatic destruction of methicillin-resistant Staphylococcus aureus infections with a simple combination of amoxicillin and light-activated methylene blue

BACKGROUND

Staphylococcus aureus is and continues to be a leading cause of bacterial infections throughout the world. Given the global dissemination of multi-drug resistant (MDR) S. aureus, particularly methicillin-resistant S. aureus (MRSA), novel solutions against S. aureus infections are urgently needed. In our study on the interactions between commonly used photosensitizers and antibiotics in the clinic, we discovered that MRSA can be dramatically destroyed by a simple combination of amoxicillin and light-activated methylene blue (MB).

METHODS

To guide the clinical application of this combination therapy, we quantitatively assessed the interaction between light-activated MB and amoxicillin against S. aureus and its treatment order, dosage, and time length dependence. Furthermore, we evaluated the efficacy of this combination therapy in treating and halting the progression of MRSA infections with the catheter biofilm infection model and the pig skin burn infection model. In the end, we disclosed the antimicrobial mechanisms of this combination therapy to further facilitate its clinical translation.

RESULTS

Amoxicillin and light-activated MB can mutually boost each other's uptake in S. aureus, producing up to 8 logs of reduction of MRSA infections when they are co-administrated. Such an anti-S. aureus synergy could be triggered with the currently used MB and amoxicillin clinical administration regimens. It is effective against S. aureus pathogens regardless of their antibiotic resistance backgrounds and does not create significant bacterial resistance with five days of continuous applications. It can lead to more than 99% of reduction of S. aureus infections established not only on the medical devices but also on the body surfaces.

CONCLUSIONS

Possessing a fusion of effectiveness, safety, sustainability, and broad applicability, this simple combination of light-activated MB and amoxicillin can ultimately reform our treatment against MDR S. aureus pathogens including MRSA, significantly alleviating the health and economic burden of S. aureus infections across the world.

An insight into photodynamic therapy towards treating major dermatological conditions

Photodynamic therapy (PDT), as the name suggests is a light-based, non-invasive therapeutic treatment method that has garnered immense interest in the recent past for its efficacy in treating several pathological conditions. PDT has prominent use in the treatment of several dermatological conditions, which consequently have cosmetic benefits associated with it as PDT improves the overall appearance of the affected area. PDT is commonly used for repairing sun-damaged skin, providing skin rejuvenation, curbing pre-cancerous cells, treating conditions like acne, keratosis, skin-microbial infections, and cutaneous warts, etc. PDT mediates its action by generating oxygen species that are involved in bringing about immunomodulation, suppression of microbial load, wound-healing, lightening of scarring, etc. Although there are several challenges associated with PDT, the prominent ones being pain, erythema, insufficient delivery of the photosensitizing agent, and poor clinical outcomes, still PDT stands to be a promising approach with continuous efforts towards maximizing clinical efficacy while being cautious of the side effects and working towards lessening them. This article discusses the major skin-related conditions which can be treated or managed by employing PDT as a better or comparable alternative to conventional treatment approaches such that it also brings about aesthetic improvements thereof.

Combination of photodynamic antimicrobial chemotherapy and ciprofloxacin to combat S. aureus and E. coli resistant biofilms

Photodynamic antimicrobial chemotherapy (PACT) coupled with an antibiotic, ciprofloxacin (CIP), was investigated using two indium metallated cationic photosensitizers, a porphyrin (1) and a phthalocyanine (2). Applying PACT followed by the antibiotic treatment led to a remarkable reduction in the biofilm cell survival of two antibiotic-resistant bacterial strains, S. aureus (Gram-positive) and E. coli (Gram-nenative). Treating both bacteria strains with PACT alone showed no significant activity at 32 µM with 15 min irradiation, while CIP alone exhibited a minimum biofilm inhibition concentration (MBIC) at 4 and 8 µg/mL on S. aureus and E. coli, respectively following 24 h incubation. The combined treatment resulted in the complete eradication of the matured biofilms with high log₁₀ reduction values of 7.05 and 7.20 on S. aureus and E. coli, respectively, at low concentrations. It was found that 15 min PACT irradiation of 8 µM of complexes (1 and 2) combined with 2 µg/mL of CIP have a 100% reduction of the resistant S. aureus biofilms. Whereas the total killing of E. coli was obtained when combining 8 µM of complex 1 and 16 µM of complex 2 both combined with 4 µg/mL of CIP.

Photoinactivation of non-tuberculous mycobacteria using Zn-phthalocyanine loaded into liposomes

Non-tuberculous mycobacteria are a heterogeneous group of environmental bacteria and other than the well-known Mycobacterium tuberculosis complex and Mycobacterium leprae. They could cause localized or disseminated infections. Mycobacterium chelonae and Mycobacterium fortuitum are among the most clinically relevant non-tuberculous mycobacteria species. The infections treatment is complex since they are resistant to antituberculosis drugs and the biofilm formation makes them impermeable to several antibiotics. Antimicrobial photodynamic therapy (aPDT) constitutes an alternative to eliminate pathogens, principally those antimicrobials resistant. Among explored photosensitizers, phthalocyanines are considered excellent, but with a disadvantage: a lack solubility in aqueous media. Consequently, several nanocarriers have been studied in the last years. In this work, a Zn-phthalocyanine into liposomes was evaluated to photoinactivate M. fortuitum and M. chelonae. The results show a higher photodynamic activity of ZnPc into liposomes respect to solution. Furthermore, M. fortuitum was more sensible to aPDT than M. chelonae.

Photodynamic therapy, a promising treatment approach for cutaneous infectious granulomas

Cutaneous infectious granulomas are mainly caused by fungi and bacteria. Antibiotics are the primary therapeutic choices for the diseases, but the drug-resistant pathogens become increasingly prevalent. Thus, there is an urgent need to explore novel approaches to treating cutaneous infectious granulomas. Photodynamic therapy (PDT) is widely used as an alternative treatment for various kinds of skin diseases, and evidence has been accumulating that PDT is also effective for the treatment of cutaneous infectious granulomas. In this narrative review, we sought to summarize the recent literature concerning the applications and mechanisms of PDT in the treatment of cutaneous infectious granulomas. Clinical and basic research has demonstrated that PDT is an effective approach in treating fungal infections such as sporotrichosis and chromoblastomycosis. In addition, PDT is also used to treat atypical mycobacterial infections such as Mycobacterium marinum. PDT can significantly shorten the duration of antibiotics treatment, resulting in diminishment of adverse effects. The potential mechanisms of PDT are to kill the pathogens directly or elicit modulatory effects on the immune microenvironments. We conclude that PDT is a promising therapeutic choice for the treatment of cutaneous infectious granulomas.

In vitro study of the effect of ALA-PDT on Mycobacterium abscessus and its antibiotic susceptibility

BACKGROUND

The skin infection caused by Mycobacterium abscessus (M. abscessus) is extremely difficult to treat in clinical practice. PDT (photodynamic therapy) is a promising antibacterial treatment. We evaluated the effect of photodynamic therapy using 5-aminolevulinic acid (ALA) as a photosensitizer on M. abscessus and its antibiotic resistance in this study.

METHODS

M. abscessus and biofilm were treated with different concentrations of ALA and then irradiated with LED light (635 nm, 80 J/cm²), while there were ALA-only group, light-only group, and negative control group. The effects were observed by colony counting, crystal violet staining, confocal laser scanning microscope (CLSM), and scanning electron microscope (SEM). The changes of drug susceptibility of M. abscessus at sublethal doses were detected by micro-broth dilution method, and the possible mechanism was explored by fluorometer and real-time fluorescence quantitative Polymerase Chain Reaction (RT-qPCR).

RESULTS

ALA-PDT showed a significant killing effect on M. abscessus at ALA concentrations greater than 50 μg/ml and the effect increased with increasing photosensitizer concentrations. ALA-PDT also showed a notable scavenging effect on M. abscessus biofilm, which was also enhanced with increasing ALA concentrations. At sublethal doses, the susceptibility of M. abscessus to antibiotics was increased, and ALA-PDT greatly increased the cell wall permeability of M. abscessus and decreased the mRNA expression of drug resistance genes whiB7 and erm (41), as well as efflux pump genes MAB_1409c and MAB_3142c at the transcriptional level.

CONCLUSIONS

ALA-PDT has a significant killing effect on M. abscessus and can increase its antibiotic susceptibility.

Effectiveness of photodynamic therapy with 5-aminolevulinic acid for Bowenoid papulosis: a retrospective study with long-term follow-up

BACKGROUND

Bowenoid papulosis (BP) is a rare infectious skin disease that occurs in sexually active young people. BP is associated with human papillomavirus (HPV)16 and 18 infections, spreads through sexual contact, and tends to become cancerous. Currently, there are different BP treatment methods, and few reports on the efficacy of photodynamic therapy (PDT) with 5-aminolevulinic acid (ALA) (ALA-PDT). We compared the differences in the clearance and recurrence rates of BP between the ALA-PDT group and other groups, and explored methods to improve clinical effects and reduce lesion recurrence by combining clinical retrospective data.

METHODS

We enrolled patients who were diagnosed with bowel papulosis" between January 1, 2009, and December 31, 2020. Patient information, such as ID number, hospitalization number, admission time, name, age, gender, telephone number, admission record, discharge record, outpatient medical history, HPV type analysis, histopathological examination, and treatment plan were recorded. Outcomes were obtained and recorded through outpatient visits, telephone, and online follow-ups from patients who had reached the treatment endpoint. We compared and evaluated the differences in lesion clearance rate, lesion recurrence rate, and patient satisfaction between the ALA-PDT group and other groups using statistical analysis.

RESULTS

The lesion clearance rate of the ALA-PDT group was significantly higher than that of the control group, the lesion recurrence rate was lower than that of the control group, and patient satisfaction was higher than that of the control group. The lesion clearance rate of the ALA-PDT group was higher than that of the microwave and radiofrequency groups, the lesion recurrence rate of the ALA-PDT group was significantly lower than that of the microwave and radiofrequency groups, and patient satisfaction was significantly higher than that of the microwave and radiofrequency groups. In the lesions of patients with BP, in addition to HPV16 and HPV18 types, other types were also detected, and most of them were mixed types of HPV infection. Age, sex, and duration of disease were not risk factors that affected BP recurrence.

CONCLUSIONS

ALA-PDT for BP has the advantages of high lesion clearance rate, low lesion recurrence rate, and high patient satisfaction. ALA-PDT is worthy of recommendation as the preferred treatment plan for the treatment of BP.

Applications of Antimicrobial Photodynamic Therapy against Bacterial Biofilms

Antimicrobial photodynamic therapy and allied photodynamic antimicrobial chemotherapy have shown remarkable activity against bacterial pathogens in both planktonic and biofilm forms. There has been little or no resistance development against antimicrobial photodynamic therapy. Furthermore, recent developments in therapies that involve antimicrobial photodynamic therapy in combination with photothermal hyperthermia therapy, magnetic hyperthermia therapy, antibiotic chemotherapy and cold atmospheric pressure plasma therapy have shown additive and synergistic enhancement of its efficacy. This paper reviews applications of antimicrobial photodynamic therapy and non-invasive combination therapies often used with it, including sonodynamic therapy and nanozyme enhanced photodynamic therapy. The antimicrobial and antibiofilm mechanisms are discussed. This review proposes that these technologies have a great potential to overcome the bacterial resistance associated with bacterial biofilm formation.

ALA_PDT Promotes Ferroptosis-Like Death of Mycobacterium abscessus and Antibiotic Sterilization via Oxidative Stress

Mycobacterium abscessus is one of the common clinical non-tuberculous mycobacteria (NTM) that can cause severe skin infection. 5-Aminolevulinic acid photodynamic therapy (ALA_PDT) is an emerging effective antimicrobial treatment. To explore whether ALA_PDT can be used to treat M. abscessus infections, we conducted a series of experiments in vitro. We found that ALA_PDT can kill M. abscesses. Mechanistically, we found that ALA_PDT promoted ferroptosis-like death of M. abscesses, and the ROS scavenger N-Acetyl-L-cysteine (NAC) and ferroptosis inhibitor Ferrostatin-1 (Fer-1) can mitigate the ALA_PDT-mediated sterilization. Furthermore, ALA_PDT significantly up-regulated the transcription of heme oxygenase MAB_4773, increased the intracellular Fe2+ concentration and altered the transcription of M. abscessus iron metabolism genes. ALA_PDT disrupted the integrity of the cell membrane and enhanced the permeability of the cell membrane, as evidenced by the boosted sterilization effect of antibiotics. In summary, ALA_PDT can kill M. abscesses via promoting the ferroptosis-like death and antibiotic sterilization through oxidative stress by changing iron metabolism. The study provided new mechanistic insights into the clinical efficacy of ALA_PDT against M. abscessus.

A new approach to the treatment of nontuberculous mycobacterium skin infections caused by iatrogenic manipulation: Photodynamic therapy combined with antibiotics: A pilot study

BACKGROUND

Recently, the number of nontuberculous mycobacterium (NTM) infections caused by iatrogenic procedures, especially rapid NTM skin infections, has been increasing. Due to the nonspecific clinical manifestations and nonstandard treatment guidelines, these infections are often misdiagnosed and challenging to treat.

METHODS

In this study, eight patients had NTM skin infections caused by iatrogenic procedures, and were diagnosed by bacterial culture and flight mass spectrometry tests. They were treated with 5-aminolevulinic acid-photodynamic therapy (ALA-PDT) combined with antibiotic therapy.

RESULTS

All eight patients enrolled in the study were cured with 100% efficacy after receiving combination therapy with ALA-PDT and antibiotics for 3-6 months. All patients experienced redness and pain during treatment but no other discomfort and were satisfified with the results of their treatments.

CONCLUSION

Local ALA-PDT combined with antibiotics is a safe and effective method of treating NTM skin infections.

Photodynamic and antibiotic therapy in combination against bacterial infections: efficacy, determinants, mechanisms, and future perspectives

Antibiotic treatment, the mainstay for the control of bacterial infections, is greatly hampered by the global prevalence of multidrug-resistant (MDR) bacteria. Photodynamic therapy (PDT) is effective against MDR infections, but PDT-induced bacterial inactivation is often incomplete, causing the relapse of infections. Combination of PDT and antibiotics is a promising strategy to overcome the limitation of both antibiotic treatment and PDT, exerting increased disinfection efficacy on MDR bacterial pathogens versus either of the monotherapies alone. In this review, we present an overview of the therapeutic effects of PDT/antibiotic combinations that have been developed. We further summarize the influencing factors and the governing molecular mechanisms of the therapeutic outcomes of PDT/antibiotic combinations. In the end, we provide concluding remarks on the strengths, limitations, and future research directions of PDT/antibiotic combination therapy to guide its appropriate usage and further development.

Photo-damage promoted by tetra-cationic palladium(II) porphyrins in rapidly growing mycobacteria

Antimicrobial photodynamic therapy (aPDT) has gained prominence in microbiology, especially in treating non-invasive infections. Diseases such as mycobacteriosis, which causes localized infections and has a slow treatment, tend to be future targets for this type of technology. Therefore, this study aimed to explore the action of two isomeric Pd(II)-porphyrins on fast-growing mycobacterial strains (RGM). Tetra-cationic porphyrins (4-PdTPyP and 3-PdTPyP) were synthesized and applied against standard strains of Mycobacteroides abscessus subsp. abscessus (ATCC 19977), Mycolicibacterium fortuitum (ATCC 6841), Mycolicibacterium smegmatis (ATCC 700084), and Mycobacteroides abscessus subsp. massiliense (ATCC 48898). Reactive oxygen species (ROS) scavengers were used in an attempt to determine possible ROS produced by the photosensitizers (PS) under study. Moreover, the impact of porphyrin on the mycobacterial surface was further evaluated by atomic force microscopy (AFM), and we observed significant damage on cells walls and altered nanomechanical and electrostatic adhesion properties. The results presented herein show that the positively charged porphyrin at the meta position (3-PdTPyP) was the most efficient PS against the RGM strains, and its bactericidal activity was proven in two irradiation sessions, with singlet oxygen species being the main ROS involved in this process. This study demonstrated the therapeutic potential of porphyrins, especially the 3-PdTPyP derivative.

Photodynamic Therapy Combined with Antibiotics or Antifungals against Microorganisms That Cause Skin and Soft Tissue Infections: A Planktonic and Biofilm Approach to Overcome Resistances

The present review covers combination approaches of antimicrobial photodynamic therapy (aPDT) plus antibiotics or antifungals to attack bacteria and fungi in vitro (both planktonic and biofilm forms) focused on those microorganisms that cause infections in skin and soft tissues. The combination can prevent failure in the fight against these microorganisms: antimicrobial drugs can increase the susceptibility of microorganisms to aPDT and prevent the possibility of regrowth of those that were not inactivated during the irradiation; meanwhile, aPDT is effective regardless of the resistance pattern of the strain and their use does not contribute to the selection of antimicrobial resistance. Additive or synergistic antimicrobial effects in vitro are evaluated and the best combinations are presented. The use of combined treatment of aPDT with antimicrobials could help overcome the difficulty of fighting high level of resistance microorganisms and, as it is a multi-target approach, it could make the selection of resistant microorganisms more difficult.

Photoinactivation of mycobacteria to combat infection diseases: current state and perspectives

Abstract

The spread of multi-drug-resistant bacterial strains causing serious infectious diseases dictates the development of new approaches to combat these diseases. In addition to drug resistance, the important causative agent of tuberculosis (Mycobacterium tuberculosis (Mtb)) is able to persist asymptomatically in individuals for many years, causing latent forms of tuberculosis. In such a dormant state, Mtb cells are also resistant to known antibiotics. In this regard, photodynamic inactivation (PDI) could be an effective alternative to antibiotics as its action is based on the generation of active forms of oxygen independently on the presence of specific antibiotic targets, thereby inactivating both drug-resistant and dormant bacteria. In this review, we summarise examples of the application of PDI for the elimination of representatives of the genus Mycobacteria, both in vitro and in vivo. According to published results, including photosensitisers in the PDI regime results in a significantly higher lethal effect. Such experiments were mainly performed using chemically synthesised photosensitisers, which need to be transported to the areas of bacterial infections, limiting PDI usage by surface (skin) diseases. In this regard, endogenous photosensitisers (mainly porphyrins) could be used to solve the problem of transportation. In vitro experiments demonstrate the effective application of PDI for mycobacteria, including Mtb, using endogenous porphyrins; the intracellular contents of these substances can be elevated by administration of 5-aminolevulenic acid, a precursor of porphyrin synthesis. Photodynamic inactivation can also be used for dormant mycobacteria, which are characterised by high levels of endogenous porphyrins. Thus, PDI can effectively eliminate drug-resistant mycobacteria. The exploitation of modern light-transmitting techniques opens new possibilities to use PDI in clinical settings.

Key points

•The potential effects of photodynamic inactivation of mycobacteria are critically reviewed.

•Approaches to photoinactivation of mycobacteria using exogenous and endogenous photosensitisers are described.

•Prospects for the use of photodynamic inactivation in the treatment of tuberculosis are discussed.

Photodynamic therapy improves skin antisepsis as a prevention strategy in arthroplasty procedures: A pilot study

BACKGROUND

Current standard skin antisepsis to prevent surgical site infections are ineffective to eradicate all skin-colonizing bacteria. Photodynamic therapy (PDT) has shown bactericidal effects in vitro, but no clinical study with improvements in skin antisepsis has been documented.

METHODS

We investigated the effect of methyl aminolevulinate (MAL)-PDT versus no PDT for skin antisepsis treatment (povidone-iodine/alcohol) in the groin of 10 healthy participants. Skin swabs were taken at baseline, immediately after PDT, and after skin antisepsis treatment to cultivate bacteria. At day 7 and 21, bacterial cultures were repeated before and after antisepsis treatment without PDT. Skin biopsies were performed to examine the grade of inflammation.

RESULTS

Skin-colonizing bacteria were found in all 20 participants at baseline sampling. Immediately after MAL-PDT, skin was sterile in 7 (70%) participants before and in all 10 (100%) participants after skin antisepsis treatment. In contrast, we found skin-colonizing bacteria in 5 (50%) participants of the control group receiving only skin antisepsis. After 7 and 21 days, skin sterility was similar to the baseline. We observed slight perivascular inflammation with lymphocytes and eosinophils without changes in the histomorphology of eccrine or sebaceous glands in skin biopsies. PDT was generally well tolerated except for localized redness.

CONCLUSION

MAL-PDT with skin antisepsis treatment sterilized skin immediately after its use but did not maintain sterility 7-21 days post-treatment. Due to local side effects, further clinical studies with less intensive PDT conditions or other photosensitizers are needed before PDT is integrated into clinical practice.

Evaluation of ALA-PDT combined with antibiotics for the treatment of skin ulcers with sinus tract formation: A pilot study

BACKGROUND

Photodynamic therapy (PDT) is considered an important and innovative treatment for healing skin wounds. Skin ulcers with sinus tract formation are rare and difficult to treat in the field of dermatology. Herein, we utilized optical fibers as a light source to penetrate the sinus tract and applied PDT to treat the sinus tract.

OBJECTIVES

To evaluate the efficacy and safety of 5-aminolevulinic acid photodynamic therapy (ALA-PDT) and provide insight into the use of ALA-PDT in the treatment of skin ulcers with sinus tracts.

METHODS

Seven patients with skin ulcers with sinus tract formation who were previously unsuccessfully treated with systemic antibiotics, debridement and dressing changes were examined. In the present study, these patients also received ALA-PDT treatment (the ulcers were irradiated with a red LED, and the sinus tracts were irradiated with semiconductor laser optical fibers), which was locally administered every 10 days with a total of 1-5 sessions.

RESULTS

Six patients enrolled in the study were fully cured after receiving combination therapy with ALA-PDT and antibiotics for three months. The sinus tract of one patient was cured and the ulcer area of this patient was reduced. All patients experienced varying degrees of redness and pain during treatment but no severe discomfort, and all patients were satisfied with the outcome of the treatment.

CONCLUSION

Local ALA-PDT combined with antibiotics could be a safe and effective treatment approach for skin ulcers with sinus tract formation.

A combination of photodynamic therapy and antimicrobial compounds to treat skin and mucosal infections: a systematic review

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) is a growing approach to treat skin and mucosal infections. Despite its effectiveness, investigators have explored whether aPDT can be further combined with antibiotics and antifungal drugs.

OBJECTIVE

To systematically assess the in vivo studies on the effectiveness of combinations of aPTD plus antimicrobials in the treatment of cutaneous and mucosal infections.

MATERIALS AND METHODS

Searches were performed in four databases (PubMed, EMBASE, Cochrane library databases, ClinicaTrials.gov) until July 2018. The pooled information was evaluated according to the PRISMA guidelines.

RESULTS

11 full-text articles were finally evaluated and included. The best aPDT combinations involved 5-aminolevulinic acid or phenothiazinium dye-based aPDT. In general, the combination shows benefits such as reducing treatment times, lowering drug dosages, decreasing drug toxicity, improving patient compliance and diminishing the risk of developing resistance. The mechanism of action may be that first aPDT damages the microbial cell wall or membrane, which allows better penetration of the antimicrobial drug.

LIMITATIONS

The number of studies was low, the protocols used were heterogeneous, and there was a lack of clinical trials.

CONCLUSIONS

The additive or synergistic effect of aPDT combined with antimicrobials could be promising to manage skin and mucosal infections, helping to overcome the microbial drug resistance.

Combined Antimicrobial Activity of Photodynamic Inactivation and Antimicrobials-State of the Art

Antimicrobial photodynamic inactivation (aPDI) is a promising tool for the eradication of life-threatening pathogens with different profiles of resistance. This study presents the state-of-the-art published studies that have been dedicated to analyzing the bactericidal effects of combining aPDI and routinely applied antibiotics in in vitro (using biofilm and planktonic cultures) and in vivo experiments. Furthermore, the current paper reviews the methodology used to obtain the published data that describes the synergy between these antimicrobial approaches. The authors are convinced that even though the combined efficacy of aPDI and antimicrobials could be investigated with the wide range of methods, the use of a unified experimental methodology that is in agreement with antimicrobial susceptibility testing (AST) is required to investigate possible synergistic cooperation between aPDI and antimicrobials. Conclusions concerning the possible synergistic activity between the two treatments can be drawn only when appropriate assays are employed. It must be noticed that some of the described papers were just aimed at determination if combined treatments exert enhanced antibacterial outcome, without following the standard methodology to evaluate the synergistic effect, but in most of them (18 out of 27) authors indicated the existence of synergy between described antibacterial approaches. In general, the increase in bacterial inactivation was observed when both therapies were used in combination.