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

PhotoChem Interplays: Lighting the Way for Drug Delivery and Diagnosis

Light, a non-invasive tool integrated with cutting-edge nanotechnologies, has driven transformative advancements in imaging-based diagnosis and drug delivery for cancer and bacterial treatments. This review discusses recent progress in these areas, beginning with emerging imaging technologies. Unlike traditional photosensors activated by visible light, alternative energy sources such as near-infrared (NIR) light, X-rays, and ultrasound have been extensively investigated to activate various photosensors, achieving high sensitivity, wavelength versatility, and spatial resolution for deep-tissue imaging. Moreover, to address challenges like tissue autofluorescence in real-time fluorescence imaging, afterglow luminescent nanoparticles are being developed by integrating these alternative energy sources for real-time imaging and sensing in deep tissue for precise cancer diagnosis and treatment beyond superficial tissues. In addition to deep tissue imaging, light-responsive nanomedicines are revolutionizing anticancer and antimicrobial phototherapy by enabling spatially and temporally controlled drug release. These smart nanoparticles are engineered to release therapeutic cargo at target sites in response to microenvironmental cues specific to tumors or infections. In anticancer phototherapy, these nanoparticles facilitate controlled drug release via photoisomerization, photothermal, and photodynamic processes. To enhance circulation time and specific targeting, biomimetic nanoparticles, which mimic natural anti-tumor responses by our body, have attracted increasing attention. In antimicrobial phototherapy, research has been focused on the chemical modification of the photosensitizer to enable targeted drug delivery. An intriguing strategy has recently emerged involving the development of "pro-photosensitizers" that are specifically activated within bacterial cells upon light irradiation, offering a high margin of safety. These advancements leverage photochemical reactions and nanotechnology to enhance precision therapy and diagnosis in addressing critical health challenges.

Photodynamic inactivation and its effects on the heterogeneity of bacterial resistance

Antimicrobial resistance is a growing threat to global public health, requiring innovative approaches for its control. Photodynamic inactivation (PDI) with light-activated photosensitizers has emerged as a strategy to combat resistant bacteria, challenging the intrinsic heterogeneity of bacterial populations. This study evaluates the impact of PDI on both heterogeneity and shape of the distribution profile of resistant bacterial populations, specifically on strains of Staphylococcus aureus resistant to amoxicillin, erythromycin, and gentamicin, for exploring its potential as an adjuvant therapy in the fight against bacterial resistance. Curcumin (10 µM) was used as a photosensitizer and five cycles of PDI were applied on Staphylococcus aureus strains under 450 nm irradiation of 10 J/cm² energy density. The resistance variations amongst bacterial subpopulations were investigated by calculating the minimum inhibitory concentration (MIC) before and after PDI treatment. MIC was significantly reduced by the antibiotics tested post-PDI and a reduction in the heterogeneity of bacterial populations was recorded, suggesting PDI can effectively decrease the resistance diversity of Staphylococcus aureus. The result reinforces the potential of PDI as a valuable adjuvant therapy, offering a promising avenue for mitigating bacterial resistance and promoting more effective treatment strategies against resistant infections.

Superhydrophobic Dressing for Singlet Oxygen Delivery in Antimicrobial Photodynamic Therapy against Multidrug-Resistant Bacterial Biofilms

The rise of antimicrobial resistance poses a critical public health threat worldwide. While antimicrobial photodynamic therapy (aPDT) has demonstrated efficacy against multidrug-resistant (MDR) bacteria, its effectiveness can be limited by several factors, including the delivery of the photosensitizer (PS) to the site of interest and the development of bacterial resistance to PS uptake. There is a need for alternative methods, one of which is superhydrophobic antimicrobial photodynamic therapy (SH-aPDT), which we report here. SH-aPDT is a technique that isolates the PS on a superhydrophobic (SH) membrane, generating airborne singlet oxygen (1O2) that can diffuse up to 1 mm away from the membrane. In this study, we developed a SH polydimethylsiloxane dressing coated with PS verteporfin. These dressings contain air channels called a plastron for supplying oxygen for aPDT and are designed so that there is no direct contact of the PS with the tissue. Our investigation focuses on the efficacy of SH-aPDT on biofilms formed by drug-sensitive and MDR strains of Gram-positive (Staphylococcus aureus and S. aureus methicillin-resistant) and Gram-negative bacteria (Pseudomonas aeruginosa and P. aeruginosa carbapenem-resistant). SH-aPDT reduces bacterial biofilms by approximately 3 log with a concomitant decrease in their metabolism as measured by MTT. Additionally, the treatment disrupted extracellular polymeric substances, leading to a decrease in biomass and biofilm thickness. This innovative SH-aPDT approach holds great potential for combating antimicrobial resistance, offering an effective strategy to address the challenges posed by drug-resistant wound infections.

Recovering the susceptibility of antibiotic-resistant bacteria using photooxidative damage

Multidrug-resistant bacteria are one of the most serious threats to infection control. Few new antibiotics have been developed; however, the lack of an effective new mechanism of their action has worsened the situation. Photodynamic inactivation (PDI) can break antimicrobial resistance, since it potentiates the effect of antibiotics, and induces oxidative stress in microorganisms through the interaction of light with a photosensitizer. This paper addresses the application of PDI for increasing bacterial susceptibility to antibiotics and helping in bacterial persistence and virulence. The effect of photodynamic action on resistant bacteria collected from patients and bacteria cells with induced resistance in the laboratory was investigated. Staphylococcus aureus resistance breakdown levels for each antibiotic (amoxicillin, erythromycin, and gentamicin) from the photodynamic effect (10 µM curcumin, 10 J/cm2) and its maintenance in descendant microorganisms were demonstrated within five cycles after PDI application. PDI showed an innovative feature for modifying the degree of bacterial sensitivity to antibiotics according to dosages, thus reducing resistance and persistence of microorganisms from standard and clinical strains. We hypothesize a reduction in the degree of antimicrobial resistance through photooxidative action combats antibiotic failures.

In vitro study of nanoliposomes containing curcumin and doxycycline for enhanced antimicrobial photodynamic therapy against Aggregatibacter actinomycetemcomitans

The excessive inappropriate use of systemic antibiotics has contributed to the emergence of antibiotic-resistant pathogens, which pose a significant risk to the success of treatment. This study has approached this problem by developing doxycycline-loaded liposome doped with curcumin (NL-Cur^+Dox) for combination antibacterial therapy against Aggregatibacter actinomycetemcomitans. The characterization of formulation revealed encapsulation of both drugs in NL-Cur^+Dox with an average size of 239 nm and sustained release behavior. Transmission electron microscopy analysis confirmed the vesicular-shaped nanocarriers without any aggregation or crystallization. The cytotoxic and hemolytic activities of NL-Cur^+Dox were evaluated. The anti-biofilm and anti-metabolic effects of NL-Cur^+Dox -mediated antimicrobial photodynamic therapy (aPDT) were examined. The data indicated that NL-Cur^+Dox -mediated aPDT led to a significant reduction of biofilm (82.7%, p = 0.003) and metabolic activity (75%, p < 0.001) of A. actinomycetemcomitans compared to the control. NL-Cur^+Dox had no significant cytotoxicity to human gingival fibroblast cells under selected conditions (p = 0.074). In addition, the hemolytic activity of NL-Cur^+Dox were negligible (< 5%). These findings demonstrate the potential application of such potent formulations in reducing one of the main bacteria causing periodontitis where the NL-Cur^+Dox could be exploited to achieve an improved phototherapeutic efficiency.

Combining bacteriophage and vancomycin is efficacious against MRSA biofilm-like aggregates formed in synovial fluid

Background

Biofilm formation is a major clinical challenge contributing to treatment failure of periprosthetic joint infection (PJI). Lytic bacteriophages (phages) can target biofilm associated bacteria at localized sites of infection. The aim of this study is to investigate whether combination therapy of phage and vancomycin is capable of clearing Staphylococcus aureus biofilm-like aggregates formed in human synovial fluid.

Methods

In this study, S. aureus BP043, a PJI clinical isolate was utilized. This strain is a methicillin-resistant S. aureus (MRSA) biofilm-former. Phage Remus, known to infect S. aureus, was selected for the treatment protocol. BP043 was grown as aggregates in human synovial fluid. The characterization of S. aureus aggregates was assessed for structure and size using scanning electron microscopy (SEM) and flow cytometry, respectively. Moreover, the formed aggregates were subsequently treated in vitro with: (a) phage Remus [∼10⁸ plaque-forming units (PFU)/ml], (b) vancomycin (500 μg/ml), or (c) phage Remus (∼10⁸ PFU/ml) followed by vancomycin (500 μg/ml), for 48 h. Bacterial survival was quantified by enumeration [colony-forming units (CFU)/ml]. The efficacy of phage and vancomycin against BP043 aggregates was assessed in vivo as individual treatments and in combination. The in vivo model utilized Galleria mellonella larvae which were infected with BP043 aggregates pre-formed in synovial fluid.

Results

Scanning electron microscopy (SEM) images and flow cytometry data demonstrated the ability of human synovial fluid to promote formation of S. aureus aggregates. Treatment with Remus resulted in significant reduction in viable S. aureus residing within the synovial fluid aggregates compared to the aggregates that did not receive Remus (p < 0.0001). Remus was more efficient in eliminating viable bacteria within the aggregates compared to vancomycin (p < 0.0001). Combination treatment of Remus followed by vancomycin was more efficacious in reducing bacterial load compared to using either Remus or vancomycin alone (p = 0.0023, p < 0.0001, respectively). When tested in vivo, this combination treatment also resulted in the highest survival rate (37%) 96 h post-treatment, compared to untreated larvae (3%; p < 0.0001).

Conclusion

We demonstrate that combining phage Remus and vancomycin led to synergistic interaction against MRSA biofilm-like aggregates in vitro and in vivo.

Combining povidone-iodine with vancomycin can be beneficial in reducing early biofilm formation of methicillin-resistant Staphylococcus aureus and methicillin-sensitive S. aureus on titanium surface

There is controversial clinical evidence regarding the added antibacterial benefit of locally administering antiseptic solutions or antibiotics to the infected joint space. The objectives of this in vitro study were to test the efficacy of povidone-iodine (PVP-I) and vancomycin in treating premature and developed Staphylococcus aureus biofilms grown on titanium implant surfaces. PVP-I and vancomycin were used to treat immature and developed biofilms formed by two clinical strains of S. aureus (BP043-MRSA, PB011-MSSA). S. aureus strains were grown as immature (3 h-old) or developed (24 h-old) biofilm. These biofilms were grown on titanium plasma sprayed discs. The treatment regimens tested were: 0.8% PVP-I, 500 μg/ml vancomycin as well as a combination of vancomycin and PVP-I. PVP-I was tested at 3 min, as per current clinical practice, versus 1 min treatment times. In addition, the cytotoxicity of the PVP-I and vancomycin was tested using fresh skeletal muscle tissue cores harvested from the rat's abdominal muscles using alamarBlue assay. The combination of PVP-I (3 min) and vancomycin (24 h.) showed synergistic interaction and the best efficacy against immature biofilms formed by both clinical strains. This degree of eradication was statistically significant compared to the untreated control, p < .0001. However, this combination therapy had limited efficiency against developed biofilms. Also, PVP-I alone was more effective when exposure time was 3 min instead of 1 min against immature biofilm for MRSA, p = .02, and MSSA, p = .01. PVP-I and vancomycin were not effective against developed biofilm regardless of exposure time. Also, combining PVP-I and vancomycin was not cytotoxic to muscle tissue. Combining PVP-I with vancomycin is superior in reducing viable S. aureus cells in immature biofilms grown on titanium surface without causing significant cytotoxicity to muscle tissue. Exposure times and biofilm maturity play a role in dictating the efficacy of using local antiseptics and antibiotics to treat biofilms on implant surfaces.