Antibacterial photodynamic therapy mediated by 5-aminolevulinic acid on methicillin-resistant Staphylococcus aureus

In vitro antimicrobial photodynamic therapy for methicillin-resistant Staphylococcus aureus using flexible organic light-emitting diode

The most critical aspect of managing methicillin-resistant S. aureus (MRSA) infections is preventing their spread by directly controlling MRSA. Studies have revealed that light-emitting diodes (LEDs) or lasers can be used for photodynamic therapy (PDT) to effectively kill MRSA. Organic light-emitting diodes (OLEDs) can also be used as a light source for PDT, but research cases are extremely rare, and most of them have used low-power OLEDs. Therefore, verification studies using high-power OLEDs are required to increase the utilization of OLEDs in PDT applications. In this study, we examined the inactivation effects of PDT on MRSA using a low-voltage/ high-power OLED device. The 632 nm OLED emitted 5-40 mW/cm2 of light at less than 5 V, and 22 mW/cm2 of light was selected as the optimal condition for OLED-PDT. The inactivation effects of OLED-PDT with 10 μM methylene blue (MB) against MRSA suspension (39.6 J/cm2), MRSA biofilm (79.2 J/cm2), and MRSA-inoculated porcine skin (39.6 J/cm2) were approximately 86.2%, 73.4%, and 80.2%, respectively. In conclusion, the combination of low-voltage/ high-power OLED and MB could be a promising way to reduce the risk of bacterial infection, contributing to the development of effective portable or wearable medical devices.

Enhancement of 5-Aminolevulinic Acid-Mediated Photodynamic Inactivation of Proteus mirabilis Using Phosphoric and Bisaminophosphinic Acids as Permeabilizing Agents

The purpose of this work was to examine the effect of phosphoric and bisaminophosphinic acids on the effectiveness of photoinactivation of Proteus mirabilis with 5-aminolevulinic acid (5-ALA) as a precursor of protoporphyrin IX. Two diode lasers λ = 404 nm (radiation intensity 26 mW cm-2) and λ = 630 nm (radiation intensity 55 mW cm-2) were used as sources of light. The most effective agent was (R)-(-)-1,1'-binaphthyl-2,2'-diylhydrogen phosphate, and a significant improvement in bactericidal effect of 5-ALA-aPDI was achieved by pretreating P. mirabilis with this compound at nontoxic concentrations of 0.368 mM. It was found that 15 min of blue light illumination was enough to achieve bacterial cell mortality of 99.999%. Photoelimination of this pathogen using red light was less effective, and the required killing effect (at least 99.99%) was not achieved until 45 min of exposure. The mechanism of increased pathogen destruction by the examined acids is multifaceted and includes not only the destabilization of the outer bacterial cell membrane by organophosphates but also an increase in the level of protoporphyrin IX in cells due to chelation of iron ions. Furthermore, a synergistic effect of intracellular photosensitizers and (R)-(-)-1,1'-binaphthyl-2,2'-diylhydrogen phosphate acting as an additional blue/red light-induced photosensitizer cannot be excluded.

A systematic overview of strategies for photosensitizer and light delivery in antibacterial photodynamic therapy for lung infections

Antimicrobial photodynamic therapy (aPDT) emerges as a viable treatment strategy for infections resistant to conventional antibiotics. A complex interplay of factors, including intracellular photosensitizer (PS) accumulation, photochemical reaction type, and oxygen levels, determines the efficacy of aPDT. Recent progress includes the development of modified PSs with enhanced lipophilicity and target-specific strategies to improve bacterial cell wall penetration and targeting. Nanotechnology-based approaches, such as using nanomaterials for targeted PS delivery, have shown promise in enhancing aPDT efficacy. Advancements in light delivery methods for aPDT, such as transillumination of large lesions and local light delivery using fiber optic techniques, are also being explored to optimize treatment efficacy in clinical settings. The limited number of animal models and clinical trials specifically designed to assess the efficacy of aPDT for lung infections highlights the need for further research in this critical area. The potential prospects of aPDT for lung tissue infections originating from antibiotic-resistant bacterial infections are also discussed in this review.

Optimizing Red Light-Based Photodynamic Therapy for Effective Bactericidal Action Against Fusobacterium nucleatum Subspecies

Fusobacterium nucleatum (F. nucleatum), a key pathogen implicated in periodontal disease, contributes to oral biofilm maturation and is linked to development of systemic diseases like colorectal cancer and liver cirrhosis. Photodynamic therapy (PDT) combined with 5-aminolevulinic acid (5-ALA) treatment (ALA-PDT) selectively targets F. nucleatum by inducing porphyrin accumulation. The bactericidal effect of red light-based PDT on F. nucleatum has not been evaluated previously. This study investigates the effect of ALA-PDT using red light-emitting diode (LED) light on F. nucleatum subspecies and their porphyrin accumulation. F. nucleatum subspecies were cultured with varying concentrations of 5-ALA under anaerobic conditions. Porphyrin accumulation was measured via fluorescence spectroscopy, and colony-forming units were measured to determine bacterial viability post-treatment. Additionally, other subspecies responded well to 0.01% 5-ALA, and uroporphyrin I accumulation correlated with bacterial death, revealing optimal bactericidal conditions. These results suggest that optimizing light intensity and 5-ALA concentration can significantly enhance the therapeutic potential of ALA-PDT in oral healthcare.

5-aminolevulinic acid photodynamic therapy for chronic wound infection in rats with diabetes

Recent research indicated that ulcers and peripheral vascular disease resulting from drug-resistant bacterial infections are the main causes of delayed healing in chronic diabetic wounds. 5-Aminolevulinic acid (ALA) is a second-generation endogenous photosensitizer. The therapeutic effect and mechanism of ALA-mediated photodynamic therapy (ALA-PDT) on methicillin-resistant Staphylococcus aureus (MRSA)-infected wounds in diabetic rats were investigated in this study. The results revealed the promising antibacterial effects of ALA-PDT MRSA in vitro, with a minimum inhibitory concentration and minimum bactericidal concentration of 250 and 500 μM, respectively. ALA-PDT also changed the permeability and structural integrity of bacterial cell membranes by producing reactive oxygen species. Meanwhile, ALA-PDT accelerated wound healing in MRSA-infected diabetic rats, with 5 % ALA-PDT achieving complete sterilization in 14 days and wound closure in 21 days. Treatment with 5 % ALA-PDT additionally improved the histopathological appearance of skin tissue, as well as fibrosis, inflammatory cytokine release, and angiogenesis-related protein expression. These findings indicated that ALA-PDT significantly promoted the healing of MRSA-infected wounds in diabetic rats by eliminating bacteria, inhibiting inflammation, generating granulation tissues, promoting neovascularization, and restoring damaged nerves. In addition, the healing mechanism was related to the activation of inflammatory and angiogenesis pathways through the regulation of tumor necrosis factor-alpha and interleukin-6 expression and upregulation of CD206, CD31, and VEGF. These findings underscored the potential role of ALA-PDT in promoting the healing of chronic diabetic wounds.

A novel chlorin derivative Shengtaibufen (STBF) mediated photodynamic therapy combined with iodophor for the treatment of chronic superficial leg wounds infected with methicillin-resistant Staphylococcus aureus: A retrospective clinical study

OBJECTIVE

Chronic wounds are costly and difficult to treat, resulting in morbidity and even mortality in some cases due to a high methicillin-resistant Staphylococcus aureus (MRSA) burden contributing to chronicity. We aimed to observe the antimicrobial activity and healing-promoting effect of a novel photosensitizer Shengtaibufen (STBF)-mediated antibacterial photodynamic therapy (PDT) on MRSA-infected chronic leg ulcers.

PATIENTS AND METHODS

This was a retrospective, comparative, single-center clinical study. A total of 32 patients with chronic lower limb wounds infected with MRSA from January 2022 to December 2023 were finally included in this study by searching the electronic medical records of the dermatology department of Huadong Hospital, including a group of red light combined with iodophor (control+iodophor, n=16, receiving red light once a week for 8 weeks and routine dressing change with iodophor once a day) and a group of STBF-mediated PDT (STBF-PDT) combined with iodophor (STBF-PDT+iodophor, n=16, receiving STBF-PDT and routine dressing change with iodophor once a day). STBF-PDT was performed once a week (1 mg/ml STBF, 1 h incubation, 630 nm red light, 80 J/cm2) for 8 weeks. The primary endpoints included wound clinical signs, wound size, wound-related pain, re-epithelialization score, MRSA load and wound-related quality of life (wound-QoL). Any adverse events were also recorded.

RESULTS

We found that STBF-PDT+iodophor could effectively alleviate clinical infection symptoms, accelerate wound closure, reduce average biological burden and improve wound-QoL without severe adverse events in comparison to the control+iodophor group. The STBF-PDT+iodophor group obtained a mean percentage reduction of 65.22% in wound size (from 18.96±11.18 cm2 to 6.59±7.94 cm2) and excellent re-epithelialization scores, as compared with a decrease of 30.17% (from 19.23±9.80 cm2 to 13.43±9.32 cm2) for the control+iodophor group. Significant differences in wound area were observed at week 6 (p=0.028*) and week 8 (p=0.002**). The bacterial load decreased by 99.86% (from 6.45 × 107±2.69 × 107 to 8.94 × 104±1.92 × 105 CFU/cm2, p<0.0001) in the STBF-PDT+iodophor group and 1.82% (from 6.61 × 107±2.13 × 107 to 6.49 × 107±2.01 × 107 CFU/cm2, p=0.029) in the control+iodophor group. The wound-QoL in STBF-PDT+iodophor group had a 51.62% decrease in overall score (from 29.65±9.33 at the initial to 14.34±5.17 at week 8, p<0.0001) compared to those receiving red light and routine wound care (from 30.73±17.16 to 29.32±15.89 at week 8, p=0.003). Moreover, patients undergoing STBF-PDT+iodophor exhibited great improvements in all domains of wound-QoL (physical, psychological and everyday-life), whereas the control+iodophor group ameliorated in only one field (everyday-life).

CONCLUSION

Our data confirmed that a novel photosensitizer, STBF-mediated PDT, when combined with iodophor, served as a potential modality for MRSA infection and a possible therapy for other drug-resistant microorganisms, and as a promising alternative for chronic cutaneous infectious diseases.

Effect of 5-aminolevulinic acid-mediated photodynamic therapy against Fusobacterium nucleatum in periodontitis prevention

Periodontitis, a chronic infectious disease leading to gingival atrophy and potential tooth loss through alveolar bone resorption, is closely linked to the oral microbiome. Fusobacterium nucleatum, known to facilitate late-stage bacterial colonization in the oral microbiome, plays a crucial role in the onset of periodontitis. Controlling F. nucleatum abundance is vital for preventing and treating periodontal disease. Photodynamic therapy combined with 5-aminolevulinic acid (ALA-PDT) has been reported to be bactericidal against Pseudomonas aeruginosa and Staphylococcus aureus. We aimed to investigate the bactericidal potential of ALA-PDT against F. nucleatum, which was evaluated by examining the impact of varying 5-ALA concentrations, culture time, and light intensity. After ALA-PDT treatment, DNA was extracted from interdental plaque samples collected from 10 volunteers and sequenced using the Illumina MiSeq platform. To further elucidate the bactericidal mechanism of ALA-PDT, porphyrins were extracted from F. nucleatum following cultivation with 5-ALA and subsequently analyzed using fluorescence spectra. ALA-PDT showed a significant bactericidal effect against F. nucleatum. Its bactericidal activity demonstrated a positive correlation with culture time and light intensity. Microbiota analysis revealed no significant alteration in α-diversity within the ALA-PDT group, although there was a noteworthy reduction in the proportion of the genus Fusobacterium. Furthermore, fluorescence spectral analysis indicated that F. nucleatum produced an excitable photosensitive substance following the addition of 5-ALA. Overall, if further studies confirm these results, this combined therapy could be an effective strategy for reducing the prevalence of periodontitis.

Advances in the targeted theragnostics of osteomyelitis caused by Staphylococcus aureus

Bone infections caused by Staphylococcus aureus may lead to an inflammatory condition called osteomyelitis, which results in progressive bone loss. Biofilm formation, intracellular survival, and the ability of S. aureus to evade the immune response result in recurrent and persistent infections that present significant challenges in treating osteomyelitis. Moreover, people with diabetes are prone to osteomyelitis due to their compromised immune system, and in life-threatening cases, this may lead to amputation of the affected limbs. In most cases, bone infections are localized; thus, early detection and targeted therapy may prove fruitful in treating S. aureus-related bone infections and preventing the spread of the infection. Specific S. aureus components or overexpressed tissue biomarkers in bone infections could be targeted to deliver active therapeutics, thereby reducing drug dosage and systemic toxicity. Compounds like peptides and antibodies can specifically bind to S. aureus or overexpressed disease markers and combining these with therapeutics or imaging agents can facilitate targeted delivery to the site of infection. The effectiveness of photodynamic therapy and hyperthermia therapy can be increased by the addition of targeting molecules to these therapies enabling site-specific therapy delivery. Strategies like host-directed therapy focus on modulating the host immune mechanisms or signaling pathways utilized by S. aureus for therapeutic efficacy. Targeted therapeutic strategies in conjunction with standard surgical care could be potential treatment strategies for S. aureus-associated osteomyelitis to overcome antibiotic resistance and disease recurrence. This review paper presents information about the targeting strategies and agents for the therapy and diagnostic imaging of S. aureus bone infections.

On the Possibility of Using 5-Aminolevulinic Acid in the Light-Induced Destruction of Microorganisms

Antimicrobial photodynamic inactivation (aPDI) is a method that specifically kills target cells by combining a photosensitizer and irradiation with light at the appropriate wavelength. The natural amino acid, 5-aminolevulinic acid (5-ALA), is the precursor of endogenous porphyrins in the heme biosynthesis pathway. This review summarizes the recent progress in understanding the biosynthetic pathways and regulatory mechanisms of 5-ALA synthesis in biological hosts. The effectiveness of 5-ALA-aPDI in destroying various groups of pathogens (viruses, fungi, yeasts, parasites) was presented, but greater attention was focused on the antibacterial activity of this technique. Finally, the clinical applications of 5-ALA in therapies using 5-ALA and visible light (treatment of ulcers and disinfection of dental canals) were described.

Enhanced Antibacterial Activity against Escherichia coli Based on Cationic Carbon Dots Assembling with 5-Aminolevulinic Acid

Carbon dots (CDs) with positive surface charges are considered one of the encouraging nanomedications for antibacterial applications. However, due to the distinctive membrane structure of Gram-negative bacteria, cationic CDs with relatively high concentrations are usually required for effective treatment, which might bring out serious safety issues at high doses. Therefore, it is of substantial significance to improve the killing efficiency of cationic CDs on Gram-negative bacteria at appropriately low concentrations. In this work, optimized cationic CDs (bPEI25 000-CDs) were prepared via a hydrothermal method with citric acid and branched PEI25000, which offered a positive surface potential, elimination abilities against Escherichia coli, and relatively high biosafety. The optimized bPEI25 000-CDs can further assemble with the clinical photodynamic therapy (PDT) drug 5-aminolevulinic acid (5-ALA) through electrostatic interaction. Moreover, compared with bPEI25 000-CDs and 5-ALA, the bacterial survival rate was significantly reduced by the ALA-bPEI25 000-CD-induced PDT effect. Even when the dose of bPEI25 000-CD carrier was halved, the bacterial survival could be reduced by 44.4% after light exposure compared to those incubated in the dark. The investigation of the bacterial morphology, membrane potential, and intracellular ROS production suggested that the enhanced antibacterial activity may be due to the membrane dysfunction and cell damage resulting from the high interaction between positively charged ALA-bPEI25 000-CDs and the bacterial cell membrane. Meanwhile, the cationic ALA-bPEI25 000-CDs may facilitate the cellular uptake of 5-ALA, resulting in a more efficient PDT effect. In summary, the antibacterial strategy proposed in this study will provide a novel approach for expanding the application of CD-based nanomedications.

Effect of 5-Aminolevulinic Acid Photodynamic Therapy on Aspergillus fumigatus Biofilms in Vitro

Aspergillus fumigatus biofilm development results in enhanced pathogenicity and treatment resistance. Most contemporary antibiotics, however, are unable to eliminate biofilms. In recent years, with the application of new photosensitizers and the development of treatment, ALA-PDT (5-aminolevulinic acid photodynamic treatment) has achieved remarkable curative effect in the treatment of fungal infectious diseases; however, no research has been conducted on ALA-PDT against A. fumigatus. This study investigated the inhibitory effect of ALA-PDT at various 5-aminolevulinic acid concentrations and light doses on A. fumigatus planktonic and biofilms in vitro. We found that ALA-PDT may successfully inhibit the development of A. fumigatus biofilm and disintegrate mature biofilm. After ALA-PDT treatment, the adherence rate and vitality dramatically decreased, and the biofilm's structure was severely compromised. Our findings show for the first time that ALA-PDT may be used to prevent the formation of A. fumigatus biofilm and disturb the structure of mature biofilm, and that it could be employed as a therapeutic therapy for A. fumigatus superficial infection.

Application of antimicrobial photodynamic therapy to treat subgingival multidrug-resistant bacterial infections in ICU patients

BACKGROUND

Drug-resistant bacterial infections have received much attention in recent years. Antimicrobial photodynamic therapy (aPDT) is an effective antimicrobial strategy. This study aimed to evaluate the therapeutic effect of methylene blue (MB)-mediated aPDT against subgingival multidrug-resistant (MDR) bacterial infections in intensive care unit (ICU) patients.

METHODS

Eighty-three patients who were hospitalized in the ICU of the Second Affiliated Hospital of Nanchang University from July 2019 to June 2021 were selected. The intraoral partitioned control test was conducted. Teeth that met the criteria were selected from different quadrants of the same patient, randomly divided into three groups, namely, A, B, and C, and treated with aPDT, chlorhexidine gargle, or normal saline. The counts of MDR bacteria in the gingival crevicular fluid were assessed in the different groups at different time points before and after treatment.

RESULTS

The MDR bacterial count decreased immediately after aPDT and was significantly different from that in the chlorhexidine gargle rinse group and the normal saline rinse group (P<0.05). There was no significant difference among the three groups at 6, 12, and 24 hours after treatment (P>0.05).

CONCLUSION

aPDT can be used to treat subgingival MDR bacterial infections, but the long-term effects of treatment need to be further studied.

Hemithioindigo-Based Visible Light-Activated Molecular Machines Kill Bacteria by Oxidative Damage

Antibiotic resistance is a growing health threat. There is an urgent and critical need to develop new antimicrobial modalities and therapies. Here, a set of hemithioindigo (HTI)-based molecular machines capable of specifically killing Gram-positive bacteria within minutes of activation with visible light (455 nm at 65 mW cm-2 ) that are safe for mammalian cells is described. Importantly, repeated exposure of bacteria to HTI does not result in detectable development of resistance. Visible light-activated HTI kill both exponentially growing bacterial cells and antibiotic-tolerant persister cells of various Gram-positive strains, including methicillin-resistant S. aureus (MRSA). Visible light-activated HTI also eliminate biofilms of S. aureus and B. subtilis in as little as 1 h after light activation. Quantification of reactive oxygen species (ROS) formation and protein carbonyls, as well as assays with various ROS scavengers, identifies oxidative damage as the underlying mechanism for the antibacterial activity of HTI. In addition to their direct antibacterial properties, HTI synergize with conventional antibiotics in vitro and in vivo, reducing the bacterial load and mortality associated with MRSA infection in an invertebrate burn wound model. To the best of the authors' knowledge, this is the first report on the antimicrobial activity of HTI-based molecular machines.

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.

Phototherapy and optical waveguides for the treatment of infection

With rapid emergence of multi-drug resistant microbes, it is imperative to seek alternative means for infection control. Optical waveguides are an auspicious delivery method for precise administration of phototherapy. Studies have shown that phototherapy is promising in fighting against a myriad of infectious pathogens (i.e. viruses, bacteria, fungi, and protozoa) including biofilm-forming species and drug-resistant strains while evading treatment resistance. When administered via optical waveguides, phototherapy can treat both superficial and deep-tissue infections while minimizing off-site effects that afflict conventional phototherapy and pharmacotherapy. Despite great therapeutic potential, exact mechanisms, materials, and fabrication designs to optimize this promising treatment option are underexplored. This review outlines principles and applications of phototherapy and optical waveguides for infection control. Research advances, challenges, and outlook regarding this delivery system are rigorously discussed in a hope to inspire future developments of optical waveguide-mediated phototherapy for the management of infection and beyond.

Efficacy of the therapy of 5-aminolevulinic acid photodynamic therapy combined with human umbilical cord mesenchymal stem cells on methicillin-resistant Staphylococcus aureus-infected wound in a diabetic mouse model

BACKGROUND

A distressing issue of diabetic ulcer (DU) is its poor healing feature with limited clinical solutions. We have previously shown that 5-aminolevulinic acid photodynamic therapy (ALA-PDT) is a promising alternative to the currently limited measures for DU. Mesenchymal stem cells (MSCs) transplantation has been believed to impose certain therapeutic effect on restoration of injury. Thus, this study aims to explore whether the combination of MSCs and ALA-PDT will exert a more advanced curative effect on DU.

METHODS

Diabetic mice were induced by intraperitoneal injection of streptozotocin (STZ, 60 mg/kg/d) for consecutive 5 days. A full-thickness skin injury (diameter 6 mm) was created in the center of the back of each mouse, and then 10 μl of methicillin-resistant Staphylococcus aureus (MRSA) suspension was added to establish an infected DU model. All DU models were randomly divided into four groups: Untreated group, MSCs group, ALA-PDT group, and ALA-PDT combined with human umbilical cord mesenchymal stem cells (hUC-MSCs) (ALA-PDT + MSCs) group. The wound sizes were recorded by a digital camera, and the healing rates were calculated using Image J software. Bacterial loads on wounds were measured using CFU (Colony forming units) analysis. The epithelialization, inflammatory cells infiltration and granulation tissue formation were monitored by Haematoxylin and eosin (H&E) staining, and the corresponding semi-quantitative score was matched. Growth and pro-inflammatory cytokines were detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Either ALA-PDT or injection of hUC-MSCs resulted in a rapid wound closure compared with the untreated, while their combination brought about the most prominent healing. On day 12, healing rates of the untreated, MSCs, ALA-PDT and ALA-PDT + MSCs were 40.56% ± 7.06%, 74.23 ± 4.83%, 84.03 ± 3.53%, 99.67 ± 0.49%, respectively. The bacterial burden reductions were approximately 1.58 logs (97.36%, P < 0.05), 2.34 logs (99.54%, P < 0.01), 4.50 logs (nearly 100%, P < 0.001) for MSCs, ALA-PDT and ALA-PDT + MSCs, respectively. Histology revealed reduced inflammatory cells and improved collagen precipitation and angiogenesis after hUC-MSCs and ALA-PDT treatment compared to the untreated. The combined therapy leaded to a more intact epithelium, similar to the healthy. Finally, ELISA revealed that the property of ALA-PDT to stimulate transforming growth factor-β1 (TGF-β1) and vascular endothelial growth factor (VEGF) and inhibit IL (interleukin) -1β and IL-6 outweighed that of hUC-MSCs, and this function of the combination overwhelmed that of any single therapy.

CONCLUSIONS

Our findings indicated that the strategy of combining ALA-PDT with hUC-MSCs possessed a significantly enhanced therapeutic effect over either single therapy, providing a promising innovative therapeutic candidate for refractory wounds.

Octenidine dihydrochloride treatment of a meticillin-resistant Staphylococcus aureus biofilm-infected mouse wound

OBJECTIVE

This study sought to estimate the effect of a liquid octenidine dihydrochloride (OCT)-impregnated gauze dressing in the treatment of meticillin-resistant Staphylococcus aureus (MRSA) biofilm-infected wounds.

METHOD

In this animal study, a six-millimetre punch full-thickness wound on each mouse back was inoculated with MRSA suspension, and then covered with a Tegaderm (3M Health Care, US) dressing for an established biofilm model. Animals were divided into three groups for topical application: control group (treated with phosphate-buffered saline, PBS); mupirocin group (treated with 2% mupirocin); and OCT group (treated with OCT). All applications were administrated once 24 hours post-wounding. The bioburden was determined by counting colony-forming units (cfus) and the biofilm architecture was viewed using fluorescent staining and scanning electron microscopy (SEM) on day two. The tissue repair was evaluated histologically and the related genes were detected by reverse transcription quantitative polymerase chain reaction (RT-qPCR) on day 15.

RESULTS

The results suggested OCT accelerated healing and reduced by >3.6 log cfu/g bacterial counts on the wounds relative to the PBS-treated control (p<0.05). Histological analysis showed OCT-treated tissue exhibited lower burden of the inflammatory cells, more mature collagen fibres and well-defined epithelialisation. LIVE/DEAD fluorescent staining and SEM confirmed OCT induced a substantial destruction to biofilm structure. RT-qPCR further demonstrated that OCT therapy could inhibit the expression of MRSA and its biofilm genes by nearly 100% (p<0.05).

CONCLUSION

This investigation provides a rare in vivo experimental basis for OCT improvement on MRSA-infected wound healing and the superior efficacy implies OCT topical application may represent an ideal choice to address established bacterial biofilm in hard-to-heal wounds.

Targeting Bacterial Membrane Proteins to Explore the Beneficial Effects of Natural Products: New Antibiotics against Drug Resistance

Antibiotic resistance is currently a world health crisis that urges the development of new antibacterial substances. To this end, natural products, including flavonoids, alkaloids, terpenoids, steroids, peptides and organic acids that play a vital role in the development of medicines and thus constitute a rich source in clinical practices, provide an important source of drugs directly or for the screen of lead compounds for new antibiotic development. Because membrane proteins, which comprise more than 60% of the current clinical drug targets, play crucial roles in signal transduction, transport, bacterial pathogenicity and drug resistance, as well as immunogenicity, it is our aim to summarize those natural products with different structures that target bacterial membrane proteins, such as efflux pumps and enzymes, to provide an overview for the development of new antibiotics to deal with antibiotic resistance.

Photodynamic therapy for treatment of Staphylococcus aureus infections

BACKGROUND

Staphylococcus aureus is a Gram-positive spherical bacterium that commonly causes various infections which can range from superficial to life-threatening. Hospital strains of S. aureus are often resistant to antibiotics, which has made their treatment difficult in recent decades. Other therapeutic alternatives have been postulated to overcome the drawbacks of antibiotic multi-resistance. Of these, photodynamic therapy (PDT) is a promising approach to address the notable shortage of new active antibiotics against multidrug-resistant S. aureus. PDT combines the use of a photosensitizer agent, light, and oxygen to eradicate pathogenic microorganisms. Through a systematic analysis of published results, this work aims to verify the usefulness of applying PDT in treating multidrug-resistant S.aureus infections.

METHODS

This review was based on a bibliographic search in various databases and the analysis of relevant publications.

RESULTS

There is currently a large body of evidence demonstrating the efficacy of photodynamic therapy in eliminating S.aureus strains. Both biofilm-producing strains, as well as multidrug-resistant strains.

CONCLUSION

We conclude that there is sufficient scientific evidence that PDT is a useful adjunct to traditional antibiotic therapy for treating S. aureus infections. Clinical application through appropriate trials should be introduced to further define optimal treatment protocols, safety and efficay.