The combination of antimicrobial photocatalysis and antimicrobial photodynamic therapy to eradicate the extensively drug-resistant colistin resistant Acinetobacter baumannii

Efflux Pump Inhibitor Potentiates the Antimicrobial Photodynamic Inactivation of Multidrug-Resistant Acinetobacter baumannii

Background: Acinetobacter baumannii, a nosocomial pathogen, poses a major public health problem due to generating resistance to several antimicrobial agents. Antimicrobial photodynamic inactivation (APDI) employs a nontoxic dye as a photosensitizer (PS) and light to produce reactive oxygen species that destroy bacterial cells. The intracellular concentration of PS could be affected by factors such as the function of efflux pumps to emit PS from the cytosol. Objective: To evaluate the augmentation effect of an efflux pump inhibitor, verapamil, three multidrug-resistant A. baumannii were subjected to APDI by erythrosine B (EB). Methods and results: The combination of EB and verapamil along with irradiation at 530 nm induced a lethal effect and more than 3 log colony-forming unit reduction to all A. baumannii strains in planktonic state. In contrast, EB and irradiation alone could produce only a sublethal effect on two of the strains. Conclusions: These data suggest that verapamil increases the intracellular concentration of EB, which potentiates the lethal efficacy of APDI. Verapamil could be applied with EB and green light to improve their antimicrobial efficacy against A. baumannii-localized infections.

Photo-responsive polymeric micelles for the light-triggered release of curcumin targeting antimicrobial activity

Nanocarriers have been successfully used to solubilize, deliver, and increase the bioavailability of curcumin (CUR), but slow CUR release rates hinder its use as a topical photosensitizer in antimicrobial photodynamic therapy. A photo-responsive polymer (PRP) was designed for the light-triggered release of CUR with an effective light activation-dependent antimicrobial response. The characterization of the PRP was compared with non-responsive micelles comprising Pluronics™ P123 and F127. According to the findings, the PRP formed photo-responsive micelles in the nanometric scale (< 100 nm) with a lower critical micelle concentration (3.74 × 10^-4 M^-1, 5.8 × 10^-4 M^-1, and 7.2 × 10^-6 M^-1 for PRP, F127, P123, respectively, at 25°C) and higher entrapment efficiency of CUR (88.7, 77.2, and 72.3% for PRP, F127, and P123 micelles, respectively) than the pluronics evaluated. The PRP provided enhanced protection of CUR compared to P123 micelles, as demonstrated in fluorescence quenching studies. The light-triggered release of CUR from PRP occurred with UV light irradiation (at 355 nm and 25 mW cm^-2) and a cumulative release of 88.34% of CUR within 1 h compared to 80% from pluronics after 36 h. In vitro studies showed that CUR-loaded PRP was non-toxic to mammal cell, showed inactivation of the pathogenic microorganisms Candida albicans, Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus aureus, and decreased biofilm biomass when associated with blue light (455  nm, 33.84 J/cm²). The findings show that the CUR-loaded PRP micelle is a viable option for antimicrobial activity.

In silico and in vitro insights into the prediction and analysis of natural photosensitive compounds targeting Acinetobacter baumannii biofilm-associated protein

BACKGROUND

The spread of Acinetobacter baumannii strains has become a global concern due to its extensive antibiotic resistance and biofilm formation. To overcome it, new antimicrobial strategies have been needed. Among them, antimicrobial photodynamic therapy (aPDT) is an efficient approach against various microorganisms. This study was focused on the use of curcumin (Cur) and quercetin (Qct) as natural photosensitive compounds to improve the activity of aPDT against A. baumannii biofilm-associated protein (Bap).

MATERIALS AND METHODS

In this in silico and in vitro study, after determining drug-likeness property, ADME/Toxicity profile, and pharmacological activity of Cur and Qct, virtual screening and molecular docking were assessed to determine the potential binding modes of Cur and Qct to Bap. Then, the anti-biofilm potential of natural photosensitizers-mediated aPDT against A. baumannii was evaluated after the determination of minimum inhibitory concentration (MIC). Subsequently, reverse transcription-quantitative real-time PCR (RT-qPCR) was used to exhibit the anti-virulent effect of aPDT against the gene involved in the biofilm formation of A. baumannii RESULTS: Cur and Qct showed almost similar pharmacokinetic and pharmacodynamics properties. These natural photosensitizers obeyed all the criteria of Lipinski's rule of five principles. According to the molecular docking analysis of protein-ligand complexes, Qct and Cur with a high affinity for Bap showed binding affinity of -6.34 and -6.98 kcal/mol, respectively. According to the findings, aPDT using 4 ×, and 8 × MIC of Cur and Qct could significantly reduce A. baumannii growth in biofilm structures in comparison with the control group (P < 0.05). Also, a significant downregulation by 3.7-, and 5.2-fold in gene expression of bap was observed after treatment with sub-MIC doses of Cur- and Qct-mediated aPDT, respectively (P < 0.05).

CONCLUSIONS

In summary, the in silico analysis showed that Cur and Qct had strong binding affinity with Bap as a stable protein of A. baumannii. Furthermore, in vitro results displayed that targeted aPDT based on these natural photosensitizers can be considered a treatment against A. baumannii infections by reducing the growth of microbial biofilm and reducing the expression of bap as a gene involved in A. baumannii biofilm formation.

Metal nanoparticles against multi-drug-resistance bacteria

Antimicrobial-resistant (AMR) bacterial infections remain a significant public health concern. The situation is exacerbated by the rapid development of bacterial resistance to currently available antimicrobials. Metal nanoparticles represent a new perspective in treating AMR due to their unique mechanisms, such as disrupting bacterial cell membrane potential and integrity, biofilm inhibition, reactive oxygen species (ROS) formation, enhancing host immune responses, and inhibiting RNA and protein synthesis by inducing intracellular processes. Metal nanoparticles (MNPs) properties such as size, shape, surface functionalization, surface charges, and co-encapsulated drug delivery capability all play a role in determining their potential against multidrug-resistant bacterial infections. Silver, gold, zinc oxide, selenium, copper, cobalt, and iron oxide nanoparticles have recently been studied extensively against multidrug-resistant bacterial infections. This review aims to provide insight into the size, shape, surface properties, and co-encapsulation of various MNPs in managing multidrug-resistant bacterial infections.

Nano-Enabled Chronic Wound Healing Strategies: Burn and Diabetic Ulcer Wounds

The human skin serves as the body’s first line of defense against the environment. Diabetes mellitus (DM) and 2nd–4th degree burns, on the other hand, affect the skin’s protective barrier features. Burn wounds, hypermetabolic state, and hyperglycemia compromise the immune system leading to chronic wound healing. Unlike acute wound healing processes, chronic wounds are affected by reinfections which can lead to limb amputation or death. The conventional wound dressing techniques used to protect the wound and provide an optimal environment for repair have their limitations. Various nanomaterials have been produced that exhibit distinct features to tackle issues affecting wound repair mechanisms. This review discusses the emerging technologies that have been designed to improve wound care upon skin injury. To ensure rapid healing and possibly prevent scarring, different nanomaterials can be applied at different stages of healing (hemostasis, inflammation, proliferation, remodeling).

Exploring the Physicochemical, Mechanical, and Photocatalytic Antibacterial Properties of a Methacrylate-Based Dental Material Loaded with ZnO Nanoparticles

While resin-based materials meet the many requirements of a restorative material, they lack adequate, long-lasting antimicrobial power. This study investigated a zinc oxide nanoparticle (ZnO NP)-loaded resin-blend (RB) toward a new antimicrobial photodynamic therapy (aPDT)-based approach for managing dental caries. The results confirmed that up to 20 wt% ZnO NPs could be added without compromising the degree of conversion (DC) of the original blend. The DC achieved for the 20 wt% ZnO NP blend has been the highest reported. The effects on flexural strength (FS), shear bond strength to dentin (SBS), water sorption (WS), solubility (SL), and viability of Streptococcus mutans under 1.35 J/cm² blue light or dark conditions were limited to ≤20 wt% ZnO NP loading. The addition of up to 20 wt% ZnO NPs had a minimal impact on FS or SBS, while a reduction in the bacteria count was observed. The maximum loading resulted in an increase in SL. Furthermore, 28-day aging in 37 °C water increased the FS for all groups, while it sustained the reduction in bacteria count for the 20 wt% resin blends. Overall, the ZnO NP-loaded resin-based restorative material presents significant potential for use in aPDT.

Photodynamic therapy for treatment of infected burns

Burns are among the most debilitating and devastating forms of trauma. Such injuries are influenced by infections, causing increased morbidity, mortality, and healthcare costs. Due to the emergence of multidrug-resistant infectious agents, efficient treatment of infections in burns is a challenging issue. Antimicrobial photodynamic therapy (aPDT) is a promising approach to inactivate infectious agents, including multidrug-resistant. In this review, studies on PubMed were gathered, aiming to summarize the achievements regarding the applications of antimicrobial photodynamic therapy for the treatment of infected burns. A literature search was carried out for aPDT published reports assessment on bacterial, fungal, and viral infections in burns. The collected data suggest that aPDT could be a promising new approach against multidrug-resistant infectious agents. However, despite important results being obtained against bacteria, experimental and clinical studies are necessary yet on the effectiveness of aPDT against fungal and viral infections in burns, which could reduce morbidity and mortality of burned patients, mainly those infected by multidrug-resistant strains.

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.

Antimicrobial photodynamic therapy against Acinetobacter baumannii

Acinetobacter baumannii (A. baumannii) has emerged as a pathogen of global importance able to cause opportunistic infections on the skin, urinary tract, lungs, and bloodstream, being frequently involved in hospital outbreaks. Such bacterium can resist a variety of environmental conditions and develop resistance to different classes of antibiotics. Antimicrobial photodynamic therapy (aPDT) has been considered a promising approach to overcome bacterial resistance once it does not cause selective environmental pressure on bacteria. In this review, studies on aPDT were accessed on PubMed, and their findings were summarized regarding its efficacy against A. baumannii. The data obtained from the literature show that exogenous photosensitizers belonging to different chemical classes are effective against multidrug-resistant A. baumannii strains. However, most of such data is from in vitro studies, and additional studies are necessary to evaluate if the exogenous photosensitizers may induce selective pressure on A. baumannii and the effectiveness of such photosensitizers in clinical practice.

The Challenge of Global Emergence of Novel Colistin-Resistant Escherichia coli ST131

Escherichia coli ST131 is one of the high-risk multidrug-resistant clones with a global distribution and the ability to persist and colonize in a variety of niches. Carbapenemase-producing E. coli ST131 strains with the ability to resist last-line antibiotics (i.e., colistin) have been recently considered a significant public health. Colistin is widely used in veterinary medicine and therefore, colistin-resistant bacteria can be transmitted from livestock to humans through food. There are several mechanisms of resistance to colistin, which include chromosomal mutations and plasmid-transmitted mcr genes. E. coli ST131 is a great model organism to investigate the emergence of superbugs. This microorganism has the ability to cause intestinal and extraintestinal infections, and its accurate identification as well as its antibiotic resistance patterns are vitally important for a successful treatment strategy. Therefore, further studies are required to understand the evolution of this resistant organism for drug design, controlling the evolution of other nascent emerging pathogens, and developing antibiotic stewardship programs. In this review, we will discuss the importance of E. coli ST131, the mechanisms of resistance to colistin as the last-resort antibiotic against resistant Gram-negative bacteria, reports from different regions regarding E. coli ST131 resistance to colistin, and the most recent therapeutic approaches against colistin-resistance bacteria.

Structural and biological investigation of biogenically synthesized titanium dioxide nanoparticles: Calcination and characterization

The antimicrobial drug resistance is increasing with the passage of time due to wide and improper use of broad spectrum drugs and the demand of the new drug increases day by day. The present study was planned to encounter this problem by synthesizing titanium dioxide nanoparticles (TiO₂ NPs) by an eco-friendly route using Cannabis sativa leaves extract. The synthesized TiO₂ NPs were calcined at 100, 300, 600, and 900°C in a muffle furnace. The crystallographic parameters were studied by X-ray diffraction and the phase transition occurred above 600°C. The surface morphology of the synthesized samples was studied by transmission electron microscopy (TEM), and scanning electron microscopy (SEM) and the particle size was measured through the ImageJ software. The elemental composition and purity of all the samples were studied by performing energy dispersive X-ray (EDX). All the synthesized TiO₂ NPs were tested for their antimicrobial effect against Gram-positive and Gram-negative bacteria using the agar well diffusion method. The activity was found higher against Gram-negative bacteria and compared to Gram-positive bacteria.