Prediction of the synergistic effect of antimicrobial peptides and antimicrobial agents via supervised machine learning.

BACKGROUND: Infectious diseases not only cause severe health problems but also burden the healthcare system. Therefore, the effective treatment of those diseases is crucial. Both conventional approaches, such as antimicrobial agents, and novel approaches, like antimicrobial peptides (AMPs), are used to treat infections. However, due to the drawbacks of current approaches, new solutions are still being investigated. One recent approach is the use of AMPs and antimicrobial agents in combination, but determining synergism is with a huge variety of AMPs time-consuming and requires multiple experimental studies. Machine learning (ML) algorithms are widely used to predict biological outcomes, particularly in the field of AMPs, but no previous research reported on predicting the synergistic effects of AMPs and antimicrobial agents. RESULTS: Several supervised ML models were implemented to accurately predict the synergistic effect of AMPs and antimicrobial agents. The results demonstrated that the hyperparameter-optimized Light Gradient Boosted Machine Classifier (oLGBMC) yielded the best test accuracy of 76.92% for predicting the synergistic effect. Besides, the feature importance analysis reveals that the target microbial species, the minimum inhibitory concentrations (MICs) of the AMP and the antimicrobial agents, and the used antimicrobial agent were the most important features for the prediction of synergistic effect, which aligns with recent experimental studies in the literature. CONCLUSION: This study reveals that ML algorithms can predict the synergistic activity of two different antimicrobial agents without the need for complex and time-consuming experimental procedures. The implications support that the ML models may not only reduce the experimental cost but also provide validation of experimental procedures.

Deionized water can substitute common bleaching agents for nonvital tooth bleaching when treated with non-thermal atmospheric plasma.

The bleaching efficacy of common bleaching agents and deionized water treated with non-thermal atmospheric pressure plasma in the pulp chamber for nonvital tooth bleaching was evaluated. A total of 120 extracted human maxillary first incisors were stained using human blood. Teeth were randomly divided into eight groups (n = 15). In the first four groups, teeth were bleached using 35% hydrogen peroxide gel, 37% carbamide peroxide gel, 2:1 (w/v) sodium perborate paste, and deionized water for 30 min. In the remaining groups, bleaching agents were treated with non-thermal atmospheric plasma for 5 min inside the pulp chamber. Overall color changes (∆E) were determined using Commission Internationale de L'Eclairage Lab Colour System. The plasma-assisted tooth bleaching has not increased tooth temperature beyond 37°C. Bleaching efficacies of bleaching agents were significantly improved when treated with non-thermal atmospheric plasma compared to their application (P < 0.05). A remarkable bleaching effect was obtained when bleaching agents were substituted with water and when treated with non-thermal atmospheric plasma. Non-thermal atmospheric plasma treatment could be a novel tool for activation of bleaching agents in the pulp chamber for nonvital tooth bleaching procedure. Moreover, water could be used as a novel bleaching agent when treated with the non-thermal atmospheric plasma to eliminate possible risks which might arise from peroxide-containing agents.

Chemical Changes in Nonthermal Plasma-Treated N-Acetylcysteine (NAC) Solution and Their Contribution to Bacterial Inactivation.

In continuation of our previous reports on the broad-spectrum antimicrobial activity of atmospheric non-thermal dielectric barrier discharge (DBD) plasma treated N-Acetylcysteine (NAC) solution against planktonic and biofilm forms of different multidrug resistant microorganisms, we present here the chemical changes that mediate inactivation of Escherichia coli. In this study, the mechanism and products of the chemical reactions in plasma-treated NAC solution are shown. UV-visible spectrometry, FT-IR, NMR, and colorimetric assays were utilized for chemical characterization of plasma treated NAC solution. The characterization results were correlated with the antimicrobial assays using determined chemical species in solution in order to confirm the major species that are responsible for antimicrobial inactivation. Our results have revealed that plasma treatment of NAC solution creates predominantly reactive nitrogen species versus reactive oxygen species, and the generated peroxynitrite is responsible for significant bacterial inactivation.

Preservation of imaging capability in sensitive ultrasound contrast agents after indirect plasma sterilization.

Many injectables are not amenable to standard sterilization methods, which destroy sensitive materials. This is particularly true for ultrasound contrast agents (UCA) consisting of gas bubbles stabilized by a surfactant or polymer shell. We investigated a new method to achieve safe and effective sterilization in production by introducing dielectric-barrier discharge non-thermal plasma. A dielectric-barrier discharge was generated to first produce plasma-treated phosphate-buffered saline (PTPBS), which was used as a sterilant solution for our UCA SE61, avoiding direct heat, pressure, chemicals, or radiation. Treated samples were tested for acoustic properties in vitro and in a flow phantom, and for sterility by standard methods. Three minutes plasma treatment of phosphate-buffered saline (PBS) proved effective. The samples showed significant inactivation of inoculated bacteria upon PTPBS treatment as compared to un-treated-PBS (p=0.0022). The treated and untreated samples showed no statistical significance (p>0.05) in acoustic response or bubble diameter (mean±SEM: 2.52±0.31 µm). Nile Red was used to model intercalation of drug in the hydrophobic shell, intercalated successfully into SE61, and was unaffected by plasma treatment. The PTPBS completely sterilized suspensions of UCA, and it did not compromise the acoustic properties of the agent or its ability to retain a hydrophobic compound.

Control of multi-drug-resistant pathogens with non-thermal-plasma-treated alginate wound dressing.

BACKGROUND: Non-thermal dielectric-barrier discharge plasma (non-thermal plasma) is being investigated for use in wound healing. Alginate gel, already in clinical use, is non-toxic but has no meaningful antimicrobial property. This study reports that a non-thermal-plasma-treated alginate wound dressing has strong antimicrobial properties. METHODS: Alginate gel was treated with non-thermal plasma in room air and inoculated with bacterial pathogens. At 15 min after this, bacterial cell viability was determined by colony assay or 2,3-bis-(2-methoxy-4- nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay. The anti-biofilm efficacy of the non-thermal-plasma-treated alginate gel was investigated and the treated gel was tested against vascular endothelial cells for a cytotoxic effect. The proliferation and migration of bacterial cells before and after exposure to the treated gel were investigated with an in vitro wound testing assay. Scanning electron microscopy was used to observe changes in the gel surface associated with exposure to bacterial pathogens. The treated gel was tested against Acinetobacter baumannii, Escherichia coli, Staphylococcus aureus, S. epidermidis, Candida albicans, and C. glabrata as representative pathogens (at 10(6)-10(9) colony-forming units [CFU]/mL), and the thickness of a plasma-treated gel dressing and distance between a glass dielectric-barrier discharge plasma probe and the gel surface were kept constant. RESULTS: Non-thermal-plasma-treated alginate gel exhibited a strong biocidal property and inactivated all of the pathogens included in the study at counts of 10(8) CFU/mL and within 15 sec of treatment. The treated gel inactivated 10(9) CFU/mL of the organisms within 1 min, and 3 min of exposure to the treated gel inactivated pathogens embedded in biofilms. The plasma-treated gel showed no significant cytotoxicity, and endothelial cells exposed to the treated gel proliferated and migrated well across a wound area over a period of time. Dressings made with the treated gel retained their biocidal effects for about a month. Scanning electron microscopy showed no damage to the surfaces of treated gels, but damage to the bacterial pathogens on plasma exposure. CONCLUSION: A non-thermal-plasma-treated alginate gel dressing has the clinical potential to decontaminate wounds, prevent surgical site infection, and promote wound healing.

Calcium binding-mediated sustained release of minocycline from hydrophilic multilayer coatings targeting infection and inflammation.

Infection and inflammation are common complications that seriously affect the functionality and longevity of implanted medical implants. Systemic administration of antibiotics and anti-inflammatory drugs often cannot achieve sufficient local concentration to be effective, and elicits serious side effects. Local delivery of therapeutics from drug-eluting coatings presents a promising solution. However, hydrophobic and thick coatings are commonly used to ensure sufficient drug loading and sustained release, which may limit tissue integration and tissue device communications. A calcium-mediated drug delivery mechanism was developed and characterized in this study. This novel mechanism allows controlled, sustained release of minocycline, an effective antibiotic and anti-inflammatory drug, from nanoscale thin hydrophilic polyelectrolyte multilayers for over 35 days at physiologically relevant concentrations. pH-responsive minocycline release was observed as the chelation between minocycline and Ca(2+) is less stable at acidic pH, enabling 'smart' drug delivery in response to infection and/or inflammation-induced tissue acidosis. The release kinetics of minocycline can be controlled by varying initial loading, Ca(2+) concentration, and Ca(2+) incorporation into different layers, enabling facile development of implant coatings with versatile release kinetics. This drug delivery platform can potentially be used for releasing any drug that has high Ca(2+) binding affinity, enabling its use in a variety of biomedical applications.

Antimicrobial efficacy and wound-healing property of a topical ointment containing nitric-oxide-loaded zeolites.

Topical delivery of nitric oxide (NO) through a wound dressing has the potential to reduce wound infections and improve healing of acute and chronic wounds. This study characterized the antibacterial efficacy of an ointment containing NO-loaded, zinc-exchanged zeolite A that releases NO upon contact with water. The release rate of NO from the ointment was measured using a chemiluminescence detection system. Minimum bactericidal concentration assays were performed using five common wound pathogens, including Gram-negative bacteria (Escherichia coli and Acinetobacter baumannii), Gram-positive bacteria (Staphylococcus epidermidis and meticillin-resistant Staphylococcus aureus) and a fungus (Candida albicans). The time dependence of antimicrobial activity was characterized by performing log-reduction assays at four time points after 1-8 h ointment exposure. The cytotoxicity of the ointment after 24 h was assessed using cultured 3T3 fibroblast cells. Minimum microbicidal concentrations (MMCs) for bacterial organisms (5×10(7) c.f.u.) ranged from 50 to 100 mg ointment (ml media)(-1); the MMC for C. albicans (5×10(4) c.f.u.) was 50 mg ointment (ml media)(-1). Five to eight log reductions in bacterial viability and three log reductions in fungal viability were observed after 8 h exposure to NO-zeolite ointment compared with untreated organisms. Fibroblasts remained viable after 24 h exposure to the same concentration of NO-zeolite ointment as was used in antimicrobial tests. In parallel studies, full-thickness cutaneous wounds on Zucker obese rats healed faster than wounds treated with a control ointment. These data indicate that ointment containing NO-loaded zeolites could potentially be used as a broad-spectrum antimicrobial wound-healing dressing.

Nonthermal dielectric-barrier discharge plasma-induced inactivation involves oxidative DNA damage and membrane lipid peroxidation in Escherichia coli.

Oxidative stress leads to membrane lipid peroxidation, which yields products causing variable degrees of detrimental oxidative modifications in cells. Reactive oxygen species (ROS) are the key regulators in this process and induce lipid peroxidation in Escherichia coli. Application of nonthermal (cold) plasma is increasingly used for inactivation of surface contaminants. Recently, we reported a successful application of nonthermal plasma, using a floating-electrode dielectric-barrier discharge (FE-DBD) technique for rapid inactivation of bacterial contaminants in normal atmospheric air (S. G. Joshi et al., Am. J. Infect. Control 38:293-301, 2010). In the present report, we demonstrate that FE-DBD plasma-mediated inactivation involves membrane lipid peroxidation in E. coli. Dose-dependent ROS, such as singlet oxygen and hydrogen peroxide-like species generated during plasma-induced oxidative stress, were responsible for membrane lipid peroxidation, and ROS scavengers, such as α-tocopherol (vitamin E), were able to significantly inhibit the extent of lipid peroxidation and oxidative DNA damage. These findings indicate that this is a major mechanism involved in FE-DBD plasma-mediated inactivation of bacteria.