Photodynamic inactivation of bacteria to decolonize meticillin-resistant Staphylococcus aureus from human skin

Antimicrobial Photodynamic Therapy in the Nasal Decolonization of Maintenance Hemodialysis Patients: A Pilot Randomized Trial

RATIONALE & OBJECTIVE

Infections are an important cause of mortality among patients receiving maintenance hemodialysis. Staphylococcus aureus is a frequent etiological agent, and previous nasal colonization is a risk factor for infection. Repeated antimicrobial decolonization reduces infection in this population but can induce antibiotic resistance. We compared photodynamic therapy, a promising bactericidal treatment that does not induce resistance, to mupirocin treatment among nasal carriers of S aureus.

STUDY DESIGN

Randomized controlled pilot study.

SETTING & PARTICIPANTS

34 patients receiving maintenance hemodialysis who had nasal carriage of S aureus.

INTERVENTIONS

Patients were randomly assigned to decolonization with a single application of photodynamic therapy (wavelength of 660nm, 400mW/cm², 300 seconds, methylene blue 0.01%) or with a topical mupirocin regimen (twice a day for 5 days).

OUTCOME

Nasal swabs were collected at time 0 (when the carrier state was identified), directly after treatment completion, 1 month after treatment, and 3 months after treatment. Bacterial isolates were subjected to proteomic analysis to identify the species present, and antimicrobial susceptibility was characterized.

RESULTS

All 17 participants randomized to photodynamic therapy and 13 of 17 (77%) randomized to mupirocin were adherent to treatment. Directly after treatment was completed, 12 participants receiving photodynamic therapy (71%) and 13 participants treated with mupirocin (77%) had cultures that were negative for S aureus (risk ratio, 0.92 [95% CI, 0.61-1.38]; P=0.9). Of the patients who had negative cultures directly after completion of photodynamic therapy, 67% were recolonized within 3 months. There were no adverse events in the photodynamic therapy group.

LIMITATIONS

Testing was restricted to assessing nasal colonization; infectious complications were not assessed.

CONCLUSIONS

Photodynamic therapy is a feasible approach to treating nasal carriage of S aureus. Future larger studies should be conducted to determine whether photodynamic therapy is equivalent to the standard of care with mupirocin.

FUNDING

Government grant (National Council for Scientific and Technological Development process 3146682020-9).

TRIAL REGISTRATION

Registered at ClinicalTrials.gov with study number NCT04047914.

Photodynamic Inactivation of Bacteria in Ionic Environments Using the Photosensitizer SAPYR and the Chelator Citrate

Many studies show that photodynamic inactivation (PDI) is a powerful tool for the fight against pathogenic, multi-resistant bacteria and the closing of hygiene gaps. However, PDI studies have been frequently performed under standardized in vitro conditions comprising artificial laboratory settings. Under real life conditions, however, PDI encounters substances like ions, proteins, amino acids, and fatty acids, potentially hampering the efficacy PDI to an unpredictable extent. Thus, we investigated PDI with the phenalene-1-one based photosensitizer SAPYR against Escherichia coli and Staphylococcus aureus in the presence of calcium or magnesium ions, which are ubiquitous in potential fields of PDI applications like in tap water or on tissue surfaces. The addition of citrate should elucidate the potential as a chelator. The results indicate that PDI is clearly affected by such ubiquitous ions depending on its concentration and the type of bacteria. The application of citrate enhanced PDI especially for Gram-negative bacteria at certain ionic concentrations (e.g. CaCl₂ or MgCl₂ : 7.5 to 75 mmol l^-1 ). Citrate also improved PDI efficacy in tap water (especially for Gram-negative bacteria) and synthetic sweat solution (especially for Gram-positive bacteria). In conclusion, the use of chelating agents like citrate may facilitate the application of PDI under real life conditions.

The photosensitizer-based therapies enhance the repairing of skin wounds

Wound repair remains a clinical challenge and bacterial infection is a common complication that may significantly delay healing. Therefore, proper and effective wound management is essential. The photosensitizer-based therapies mainly stimulate the photosensitizer to generate reactive oxygen species through appropriate excitation source irradiation, thereby killing pathogenic microorganisms. Moreover, they initiate local immune responses by inducing the recruitment of immune cells as well as the production of proinflammatory cytokines. In addition, these therapies can stimulate the proliferation, migration and differentiation of skin resident cells, and improve the deposition of extracellular matrix; subsequently, they promote the re-epithelialization, angiogenesis, and tissue remodeling. Studies in multiple animal models and human skin wounds have proved that the superior sterilization property and biological effects of photosensitizer-based therapies during different stages of wound repair. In this review, we summarize the recent advances in photosensitizer-based therapies for enhancing tissue regeneration, and suggest more effective therapeutics for patients with skin wounds.

Photodynamic disinfection and its role in controlling infectious diseases

Photodynamic therapy is witnessing a revival of its origins as a response to the rise of multi-drug resistant infections and the shortage of new classes of antibiotics. Photodynamic disinfection (PDDI) of microorganisms is making progresses in preclinical models and in clinical cases, and the perception of its role in the clinical armamentarium for the management of infectious diseases is changing. We review the positioning of PDDI from the perspective of its ability to respond to clinical needs. Emphasis is placed on the pipeline of photosensitizers that proved effective to inactivate biofilms, showed efficacy in animal models of infectious diseases or reached clinical trials. Novel opportunities resulting from the COVID-19 pandemic are briefly discussed. The molecular features of promising photosensitizers are emphasized and contrasted with those of photosensitizers used in the treatment of solid tumors. The development of photosensitizers has been accompanied by the fabrication of a variety of affordable and customizable light sources. We critically discuss the combination between photosensitizer and light source properties that may leverage PDDI and expand its applications to wider markets. The success of PDDI in the management of infectious diseases will ultimately depend on the efficacy of photosensitizers, affordability of the light sources, simplicity of the procedures, and availability of fast and efficient treatments.

Novel photodynamic coating reduces the bioburden on near-patient surfaces thereby reducing the risk for onward pathogen transmission: a field study in two hospitals

BACKGROUND

Near-patient surfaces are recognized as a source for hospital-acquired infections. Such surfaces act as reservoirs for microbial contamination by which pathogens can be transmitted from colonized or infected patients to susceptible patients. Routine disinfection of surfaces only results in a temporal elimination of pathogens, and recontamination inevitably occurs shortly between disinfections.

AIM

A novel antimicrobial coating based on photodynamics was tested under laboratory conditions and subsequently in a field study in two hospitals under real-life conditions.

METHODS

Identical surfaces received a photodynamic or control coating. Bacterial counts [colony-forming units (cfu)/cm²) were assessed regularly for up to 6 months.

FINDINGS

The laboratory study revealed a mean reduction of several human pathogens of up to 4.0 ± 0.3 log₁₀. The field study in near-patient environments demonstrated mean bacterial values of 6.1 ± 24.7 cfu/cm² on all control coatings. Photodynamic coatings showed a significantly lower mean value of 1.9 ± 2.8 cfu/cm² (P<0.001). When considering benchmarks of 2.5 cfu/cm² or 5 cfu/cm², the relative risk for high bacterial counts on surfaces was reduced by 48% (odds ratio 0.38, P<0.001) or 67% (odds ratio 0.27, P<0.001), respectively.

CONCLUSION

Photodynamic coatings provide a significant and lasting reduction of bacterial counts on near-patient surfaces, particularly for high bacterial loads, in addition to routine hygiene. The promising results of this proof-of-concept study highlight the need for further studies to determine how this novel technology is correlated with the frequency of hospital-acquired infections.