Destruction Of Membrane Research Articles

A novel antimicrobial peptide found in Pelophylax nigromaculatus

BackgroundMany active peptides have been found in frog skin secretions. In this paper, our research focused on Pelophylax nigromaculatus and found a broad-spectrum antimicrobial peptide Nigrocin-PN based on the molecular cloning technique. Thereafter, the “Rana box” function was briefly studied by two mutated peptides (Nigrocin-M1 and Nigrocin-M2). Furthermore, in vitro and in vivo assays were used to characterize the peptide’s biofunctions, and the peptide’s function in treating multidrug-resistant pathogens was also studied. ResultsNigrocin-PN not only displayed potent antimicrobial abilities in vitro but also significantly ameliorated pulmonary inflammation induced by Klebsiella pneumoniae in vivo. By comparing, leucine-substituted analogue Nigrocin-M1 only displayed bactericidal abilities towards gram-positive bacteria, while the shorter analogue Nigrocin-M2 lost this function. More strikingly, Nigrocin-PN exhibited synergistic effects with commonly used antibiotics; in vitro evolution experiments revealed that coadministration between Nigrocin-PN and ampicillin could delay Staphylococcus aureus antibiotic resistance acquisition. Kinetics and morphology studies indicate that antibacterial mechanisms involved membrane destruction. Furthermore, toxicities and anticancer abilities of these peptides were also studied; compared to two analogues, Nigrocin-PN showed mild haemolytic activity and indistinctive cytotoxicity towards normal cell lines HMEC-1 and HaCaT. ConclusionsA broad-spectrum antimicrobial peptide Nigrocin-PN was discovered from the skin secretion of Pelophylax nigromaculatus. Structurally, “Rana box” played a crucial role in reducing toxicities without compromising antibacterial abilities, and Nigrocin-PN could be a desired therapeutic candidate. Graphical abstract▪ Highlights•For AMPs, disulphide bond can affect their biofunction and cytotoxicity.•Frog skin secretion is a reservoir to delve valuable peptides.•AMPs-antibiotics coadministration could be a strategy to delay drug resistance.

Biomimetic AgNPs@antimicrobial peptide/silk fibroin coating for infection-trigger antibacterial capability and enhanced osseointegration.

Endowing implant surfaces with combined antibacterial and osteogenic properties by drug-loaded coatings has made great strides, but how to achieve the combined excellence of infection-triggered bactericidal and in vivo-proven osteogenic activities without causing bacterial resistance still remains a formidable challenge. Herein, antimicrobial peptides (AMPs) with osteogenic fragments were designed and complexed on the surface of silver nanoparticle (AgNP) through hydrogen bonding, and the collagen structure-bionic silk fibroin (SF) was applied to carry AgNPs@ AMPs to achieve infection-triggered antibacterial and osteointegration. As verified by TEM, AMPs contributed to the dispersion and size-regulation of AgNPs, with a particle size of about 20 nm, and a clear protein corona structure was observed on the particle surface. The release curve of silver ion displayed that the SF-based coating owned sensitive pH-responsive properties. In the antibacterial test against S.aureus for up to 21 days, the antibacterial rate had always remained above 99%. Meanwhile, the underlying mechanism was revealed, originating from the destruction of the bacterial cell membranes and ROS generation. The SF-based coating was conducive to the adhesion, diffusion, and proliferation of bone marrow stem cells (BMSCs) on the surface, and promoted the expression of osteogenic genes and collagen secretion. The in vivo implantation results showed that compared with the untreated Ti implants, SF-based coating enhanced osseointegration at week 4 and 8. Overall, the AgNPs@AMPs-loaded SF-based coating presented the ability to synergistically inhibit bacteria and promote osseointegration, possessing tremendous potential application prospects in bone defects and related-infection treatments.

Radiation synthesis of pH-sensitive 2-(dimethylamino)ethyl methacrylate/ polyethylene oxide/ZnS nanocomposite hydrogel membrane for wound dressing application

The popularity of hydrogel membrane as wound dressing lies in its elastic physical properties and the ability to encapsulate drug particles with improved properties to meet the diverse pH-sensitive hydrogel for wound dressing materials. A pH-sensitive hydrogel membrane that consists of 2-(dimethylamino)ethyl methacrylate/polyethylene oxide (DMAEM/PEO) in the ratio of (50:50% v/v) was crosslinked by γ-irradiation at a dose of 20 kGy. The combination of ZnS nanoparticles with (DMAEM/PEO) hydrogel loaded individually and with three antibiotic drugs such as colistin (C), gentamicin (G), and neomycin (N), is a simple and effective approach for enhancing their antimicrobial activities. The novelty is superior to the antimicrobial properties of the three common antimicrobials (C, G, and N) drugs in wound dressing hydrogel membranes due to the hybrid of ZnS nanoparticles with (DMAEM/PEO) hydrogel. The drug release rate experiments showed that (C) and (N) drugs were much more released at pH 4 than at pH 7, from (33% and 99%) to (24% and 70%), respectively. In contrast, the release rate of G drug increased from 40% at pH 4 to 96% at pH 7. Furthermore, the drug release kinetics showed differential release parameters of the three drugs due to the probably intermolecular hydrogen bonds between them and hydrogels segments. Finally, the antimicrobial activity of the three drugs loaded in (DMAEM/PEO)/ZnS hydrogel was tested against different bacterial and fungal strains of wound infections in in-vitro conditions. The antimicrobial experiments showed that ZnS NPs assisted in increasing the bactericidal drugs’ activity of (C, G, and N) compared to control antimicrobial agents (AX/Nyst.). The (DMAEM/PEO)/ZnS loaded by neomycin (BNZ) hydrogel had high antimicrobial activity, initiating their action by wrapping and adhesion at the exterior surface of the pathogenic microbe cell, producing membrane destruction and changing transport potential.

Tackling Drug Resistance and Other Causes of Treatment Failure in Leishmaniasis

Leishmaniasis is a tropical infectious disease caused by the protozoan Leishmania parasite. The disease is transmitted by female sand flies and, depending on the infecting parasite species, causes either cutaneous (stigmatizing skin lesions), mucocutaneous (destruction of mucous membranes of nose, mouth and throat) or visceral disease (a potentially fatal infection of liver, spleen and bone marrow). Although more than 1 million new cases occur annually, chemotherapeutic options are limited and their efficacy is jeopardized by increasing treatment failure rates and growing drug resistance. To delay the emergence of resistance to existing and new drugs, elucidating the currently unknown causes of variable drug efficacy (related to parasite susceptibility, host immunity and drug pharmacokinetics) and improved use of genotypic and phenotypic tools to define, measure and monitor resistance in the field are critical. This review highlights recent progress in our understanding of drug action and resistance in Leishmania, ongoing challenges (including setbacks related to the COVID-19 pandemic) and provides an overview of possible strategies to tackle this public health challenge.

Antagonistic activity and mechanism of Lactobacillus rhamnosus SQ511 against Salmonella enteritidis.

Salmonella enteritidis is an important food-borne pathogen. The use of antibiotics is a serious threat to animal and human health, owing to the existence of resistant strains and drug residues. Lactic acid bacteria, as a new alternative to antibiotics, has attracted much attention. In this study, we investigated the antibacterial potential and underlying mechanism of Lactobacillus rhamnosus SQ511 against S. enteritidis ATCC13076. The results revealed that L. rhamnosus SQ511 significantly inhibited S. enteritidis ATCC13076 growth or even caused death. Laser confocal microscopic imaging revealed that the cell-free supernatant (CFS) of L. rhamnosus SQ511 elevated the reactive oxygen species level and bacterial membrane depolarization in S. enteritidis ATCC13076, leading to cell death. Furthermore, L. rhamnosus SQ511 CFS had severely deleterious effects on S. enteritidis ATCC13076, causing membrane destruction and the release of cellular materials. In addition, L. rhamnosus SQ511 CFS significantly reduced the expression of virulence, motility, adhesion, and invasion genes in S. enteritidis ATCC13076 (P < 0.05), and considerably inhibited motility and biofilm formation capacity (P < 0.05). Thus, antimicrobial compounds produced by L. rhamnosus SQ511 strongly inhibited S. enteritidis growth, mobility, biofilm formation, membrane disruption, and reactive oxygen species generation, and regulated virulence-related gene expressions, presenting promising applications as a probiotic agent.

Discovering the direct evidence of photocatalytic sterilization mechanism on bimetallic sulfides heterostructures

Despite the development of sterilization, the study of reactive oxygen species (ROS) based disinfection mechanism is still under restrictions due to the lack of direct evidence. In this work, DiI is used to explore the sterilization mechanism in-depth. The mechanism is directly proven to be that the generated ROS would seriously damage the lipid of the cell membrane. It provides direct evidence for the destruction of cell membrane for the first time. These ROS can cause the death of more than 99% of both Gram-negative and Gram-positive bacteria within 120 min under visible light. What’s more, MoS2/MSy (MSy = MnS, CuS, and CeS2) are successfully synthesized by employing Mo/M−MOF (M = Mn, Cu, and Ce) as precursors. Since bigger Fermi lever difference and smaller work function bring better photocatalytic activity, MoS2/MnS composites display superb photocatalytic activity than others. Therefore, the as-prepared materials can be widely used in environmental protection, biotechnology, and clinical therapy.

Antimicrobial activity and mechanism of isothiocyanate from Moringa oleifera seeds against Bacillus cereus and Cronobacter sakazakii and its application in goat milk

This study was conducted to investigate the antibacterial activity and mechanism of (4-[(4′-O-acetyl-α-L-rhamnosyloxy)benzyl] isothiocyanate) (RBITC) from Moringa oleifera seeds at the molecular level against Bacillus cereus (B. cereus) and Cronobacter sakazakii (C. sakazakii) and to further analyze the application of RBITC in goat milk. Antimicrobial effects were evaluated by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values. The changes in endoenzyme, entocyte, and cell morphology were thoroughly analyzed to reveal the possible mechanism of action. The results showed the MICs of RBITC against B. cereus and C. sakazakii strains were 0.14 and 0.25 mg/mL, and the MBCs were 0.28 and 0.50 mg/mL, respectively. Scanning electron microscopy results revealed marked destruction of the cell membrane upon RBITC treatment. The detection of intracellular substances (ATP, DNA, and proteins) and intracellular enzymes (β-galactosidase, ATPase, and AKP) exhibited the destructive effect of RBITC on bacterial cells and showed that RBITC treatment inhibits the activity of various intracellular enzymes of both strains of bacteria, resulting in disrupted intracellular homeostasis. Moreover, RBITC inhibited biofilm formation of B. cereus and C. sakazakii at concentrations of 1 × MIC, with biofilm formation found to decrease by 77.25% and 75.10% within 72 h. Finally, RBITC presented better antibacterial activity in goat milk without adverse effects on its quality.

Insight into the antibacterial resistance of graphdiyne functionalized by silver nanoparticles.

ObjectivesSilver nanoparticles (AgNPs) tend to aggregate spontaneously due to larger surface‐to‐volume ratio, which causes decreased antibacterial activity and even enhanced antimicrobial resistance (AMR). Here, we aim to improve the stability of AgNPs by employing a growth anchor graphdiyne (GDY) to overcome these shortcomings.Materials and Methods Bacillus subtilis and Escherichia coli were selected to represent gram‐positive and gram‐negative bacteria, respectively. Transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM)‐EDS mapping and inductively coupled plasma mass spectrometry (ICP‐MS) were carried out to characterize the physiochemical properties of materials. The antimicrobial property was determined by turbidimetry and plate colony‐counting methods. The physiology of bacteria was detected by SEM and confocal imaging, such as morphology, reactive oxygen species (ROS) and cell membrane.ResultsWe successfully synthesized a hybrid graphdiyne @ silver nanoparticles (GDY@Ag) by an environment‐friendly approach without any reductants. The hybrid showed high stability and excellent broad‐spectrum antibacterial activity towards both gram‐positive and gram‐negative bacteria. It killed bacteria through membrane destruction and ROS production. Additionally, GDY@Ag did not induce the development of the bacterial resistance after repeated exposure.ConclusionsGDY@Ag composite combats bacteria by synergetic action of GDY and AgNPs. Especially, GDY@Ag can preserve its bacterial susceptibility after repeated exposure compared to antibiotics. Our findings provide an avenue to design innovative antibacterial agents for effective sterilization.

Planktonic Growth and Biofilm Formation by Providencia rettgeri and Subsequent Effect of Tannic Acid Treatment under Food-Related Environmental Stress Conditions

Providencia rettgeri is an opportunistic foodborne pathogen with a strong biofilm-forming ability in low-nutrition environments. However, information regarding the impact of simulated food processing conditions on P. rettgeri planktonic growth and biofilm formation is limited. Using response surface methodology (RSM), the combined effects of temperature (19 to 37°C), pH (5 to 9), and sodium chloride (NaCl) concentration (0.50 to 2.0%, w/v) were applied to construct planktonic growth and biofilm formation models for P. rettgeri. For both RSM models, an increase in NaCl concentration restricted P. rettgeri growth. Planktonic growth and biofilm formation were maximum at 27.83 and 25.41°C, respectively. Tannic acid (TA) is a highly effective antibacterial agent that inhibited planktonic and biofilm P. rettgeri under optimal growth conditions. The viability of P. rettgeri cells was decreased by TA treatment, which caused destruction of the cell membrane and production of endogenous reactive oxygen species. TA significantly inactivated P. rettgeri biofilms, as verified by observation. The obtained models in this study may be useful for describing the impact of temperature, pH, and NaCl concentration on the growth by P. rettgeri in the food processing environment and better understanding the impacts of food-related conditions on bacterial planktonic growth and biofilm formation. These results obtained for P. rettgeri planktonic cells and biofilms can provide a framework for removal strategies for other foodborne pathogens.

The effect of the blood sampling method on the risk of mechanical hemolysis of erythrocytes in healthy calves and with endogenous intoxication syndrome

In the conditions of the milk production complex in the Voronezh region, where Holstein cattle are kept, studies were conducted to study the degree of injury to blood cells during its selection by various methods in healthy calves and with endogenous intoxication syndrome. In healthy animals, blood sampling by passive leakage does not affect the membranes of erythrocytes. When using vacuum systems, there are no visual signs (hemolysis) of cell destruction, but changes in their cytoskeleton occur with an increase in the sensitivity of membranes to negative pre-analytical factors. In animals with endogenous intoxication syndrome, there are explicit or hidden destruction of erythrocyte membranes, which are manifested by an increase in the content of extra-erythrocyte hemoglobin, the degree of physiological hemolysis, sensitivity to intra- and extravascular hemolytic factors. As a result, already when selecting blood samples by passive gravity, there is a risk of hemolysis, and when using a vacuum system, it is observed in most samples. Therefore, when examining sick animals, it is necessary to take into account the high probability of laboratory diagnostic error at the pre-analytical stage that occurs due to hemolysis of erythrocytes with hypersensitivity to extravascular cytolytic factors, including mechanical effects during blood sampling.

Terminal Complement Inhibitor Ravulizumab in Generalized Myasthenia Gravis

BackgroundGeneralized myasthenia gravis (gMG) is a rare, chronic, and debilitating autoimmune disease. Activation of the complement system by autoantibodies against the postsynaptic acetylcholine receptor (AChR) leads to destruction of the postsynaptic membrane and disruption of neuromuscular transmission. This trial evaluated ravulizumab, a long-acting inhibitor of terminal complement protein C5, as a treatment for gMG.MethodsIn this randomized, double-blind, placebo-controlled, multinational trial, we randomly assigned (1:1) patients with anti-AChR antibody-positive gMG to intravenous ravulizumab or placebo for 26 weeks. Patients received a loading dose on day 1, followed by maintenance doses on day 15 and every 8 weeks thereafter. The primary end point and first secondary end point (change from baseline to week 26 in patient-reported Myasthenia Gravis–Activities of Daily Living [MG-ADL] scale and clinician-reported Quantitative Myasthenia Gravis [QMG] total scores, respectively) were compared between the ravulizumab- and placebo-treated groups.ResultsIn total, 175 patients were enrolled. Ravulizumab significantly increased the magnitude of mean changes from baseline to week 26 versus placebo in MG-ADL (−3.1 vs. −1.4; P<0.001) and QMG (−2.8 vs. −0.8; P<0.001) total scores. Improvements in both measures occurred within 1 week of ravulizumab initiation and were sustained through week 26. QMG total scores improved by 5 points or more in a significantly greater proportion of ravulizumab-treated patients than of those receiving placebo (30.0% vs. 11.3%; P=0.005). No notable differences in adverse events were observed.ConclusionsRavulizumab demonstrated rapid and sustained improvements in both patient- and clinician-reported outcomes and had a side effect and adverse-event profile that did not limit treatment in adults with anti-AChR antibody-positive gMG. (Funded by Alexion, AstraZeneca Rare Disease; ClinicalTrials.gov number, NCT03920293; EudraCT number, 2018-003243-39.)

Blue Light Induces RPE Cell Necroptosis, Which Can Be Inhibited by Minocycline.

Purpose:Damage to and death of the retinal pigment epithelium (RPE) are closely related to retinal degeneration. Blue light is a high-energy light that causes RPE damage and triggers inflammatory responses. This study investigates whether blue light induces RPE necroptosis, explores pharmacologic therapy and specific mechanisms, and provides hints for research on retinal degeneration.MethodsThe human RPE cell line ARPE-19 was cultured and subjected to blue light insult in vitro. Annexin V/PI was used to evaluate RPE survival. Minocycline was applied to inhibit the death of RPE. Proteomic measurement was used to analyze protein expression. Inhibitors of necroptosis and apoptosis were applied to assess the death mode. Immunofluorescence of protein markers was detected to analyze the mechanism of cell death. Subcellular structural changes were detected by transmission electron microscopy. Reactive oxygen species (ROS) was tested by DCFH-DA. Mitochondrial membrane potential (Δψm) was detected by JC-1. BALB/c mice received bule light exposure, and RPE flatmounts were stained for verification in vivo.ResultsBlue light illumination induced RPE death, and minocycline significantly diminished RPE death. Proteomic measurement showed that minocycline effectively mitigated protein hydrolysis and protein synthesis disorders. Necroptosis inhibitors (Nec-1s, GSK-872) increased the survival of RPE cells, but apoptosis inhibitors (Z-VAD-FMK) did not. After blue light illumination, high-mobility group box-1 (HMGB1) was released from the nucleus, receptor-interacting protein kinase 3 (RIPK3) aggregated, and mixed-lineage kinase domain-like protein (MLKL) increased in the RPE. The application of minocycline alleviated the above phenomena. After blue light illumination, RPE cells exhibited necrotic characteristics accompanied by destruction of cell membranes and vacuole formation, but nuclear membranes remained intact. Minocycline improved the morphology of RPE. Blue light increased ROS and decreased Δψm of RPE, minocycline did not reduce ROS but kept Δψm stable. In vivo, HMGB1 release and RIPK3 aggregation appeared in the RPE of BALB/c mice after blue light illumination, and minocycline alleviated this effect.ConclusionsBlue light exposure causes RPE necroptosis. Minocycline reduces the death of RPE by keeping Δψm stable, inhibiting necroptosis, and preventing HMGB1 release. These results provide new ideas for the pathogenesis and treatment of retinal degeneration.

On the molecular mechanism of nonspecific antimicrobial action of protonated diallylammonium polymers on mycobacterial cells

The protonated diallylammonium polymers (PDAA) are known to possess a high antimicrobial activity relative to a broad scope of pathogens, unlike their quaternary analog poly(N, N-diallyl-N, N-dimethylammonium chloride) (PDADMAC). Moreover, PDAA exhibits nonspecific antimicrobial activity relative to Mycobacterium tuberculosis, in contrast to known quaternary polymeric and low-molecular-weight biocides. The present paper is devoted to studying, using several physicochemical methods, the different facets of the interaction of secondary poly (diallylammonium trifluoroacetate) (PDAATFA) with Mycobacterium smegmatis – the nearest fast-growing relative of M. tuberculosis in comparison with the action of PDADMAC. We studied the interaction between polymer and phenolic glycolipids molecules (PGL) (i.e., molecules of the outer leaflet of both M. smegmatis and M. tuberculosis cell wall) by FTIR. We used phenyl-β-D-glucuronide as a model compound whose structure is close to that of the glycosylated phenolic part of the PGL molecule. It was assessed the polymer effect on transmembrane potential (TM) and permeability barrier of M. smegmatis. It was studied the biocidal activity of the polymers relative to M. smegmatis. The cytotoxic effect of PDAATFA on M. smegmatis cells was analyzed by TEM. We have proved the direct interaction of polymers with the outer membrane molecules for the first time. FTIR and the rest data show a formation of the non-covalent intermolecular hydrogen-bonded complex between protonated PDAATFA polymers and phenolic glycolipids that leads to the destruction of the mycobacterial outer membrane and, as a result, cell death. We believe that because of the structural similarity of cell wall chemistry and organization, this conclusion is proper for model organism M. smegmatis and pathogenic M. tuberculosis. Contrary to expected, the action of more hydrophobic PDADMAC does not lead to a destruction of the outer membrane but to a gradual suppression of the TM potential and cell death due to inhibition of general bioenergetic processes over the extended treatment time.

Monitoring the Adhesion and Inhibitory Activity of Candida albicans on Poly‐l‐Lysine Modified Gold Nano‐Match Head Arrays

AbstractA platform for real‐time monitoring and comprehensively studying the adhesion process of microorganisms onto material surfaces as well as their bioactivity on the surface is very helpful to reveal the microbial contamination mechanism on drainage catheters, intravascular stents, and implanted sensors. Herein, a multifunctional sensor based on localized surface plasmon resonance of gold nano‐match head arrays (GNMAs) is developed for monitoring the adhesion behavior of microorganisms (such as Candida albicans, i.e., C. albicans) as well as its inhibitory activity. The sensor is fabricated through soft lithography processes using nanopatterned polydimethylsiloxane stamps, and modified with polymers of different charges for investigating the adhesion of C. albicans onto different charged surfaces. The spectroscopic study shows that C. albicans are more favorable to positively charged surfaces than negatively charged ones, which is also proven by the fluorescence images under microscope. Moreover, the authors demonstrate that the GNMA modified with poly‐l‐lysine (PLL) can effectively kill the adhered C. albicans due to the membrane destruction and the reactive oxygen species induced by PLL. These unique advantages suggest that the sensor is capable as both an antifungal study system and a real‐time monitoring platform for antifungal performance evaluation.

A modified flower pollen-based photothermocatalytic process for enhanced solar water disinfection: Photoelectric effect and bactericidal mechanisms

Solar disinfection (SODIS) is regarded as an affordable and effective point-of-use (POU) water disinfection treatment urgently needed in rural developing world. This work developed an enhanced SODIS scheme that utilized a novel flower pollen-based catalyst (Te-TRP). The bench-scale experiments demonstrated 100% photothermocatalytic inactivation of approximately 7-log E. coli K-12, Spingopyxis sp. BM1-1, or S. aureus bacterium by Te-TRP within 40–60 min. Moving toward practical device design, we constructed a flow-through reactor and demonstrated the outstanding water disinfection performance of Te-TRP. The in-depth mechanistic study revealed the synergetic effect between photocatalysis and photothermal conversion and identified the bacterial inactivation pathway. 1O2 and ·O2¯ were verified to be the dominant reactive oxygen species involved in the bacterial inactivation. The damage to bacterial cells caused by photothermocatalytic reactions was systematically investigated, demonstrating the cell membrane destruction, the loss of enzyme activity, the increased cell membrane permeability, and the complete inactivation of bacteria without the viable but nonculturable state cells. This work not only affords a facile approach to preparing biomaterial-based catalysts capable of efficient photothermocatalytic bacterial inactivation, but also proposes a prototype of POU water treatment, opening up an avenue for sustainable environmental remediation.

In vitro Antimicrobial Activity and the Mechanism of Berberine Against Methicillin-Resistant Staphylococcus aureus Isolated from Bloodstream Infection Patients.

PurposeTo investigate the antimicrobial activity of berberine and the mechanism by which it combats methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from patients with bloodstream infections.MethodsFifteen clinical MRSA isolates were collected, and their Multi-locus Sequence Types (MLST) were examined. The minimum inhibitory concentration (MIC) and combined antibacterial activity of berberine alone, and when combined with clindamycin and rifampicin separately, were determined. Additionally, two MRSA strains (ST239 and ST5) were selected to perform the time-killing assay and biofilm formation test. Cell wall alterations and cell membrane integrity were measured by confocal laser scanning microscopy (CLSM) and electron microscopy to assess the influence on cell morphology.ResultsOur data showed berberine was effective against MRSA at MIC values varying from 256 to 64 mg*L−1 for different MLST types. Berberine alone, and when combined with clindamycin and rifampicin separately, displayed excellent antibacterial activity which reduced the bacterial counts by 2lgCFU*mL within 24h and significantly weakened biofilm formation compared with control strain. Additionally, bacterial cytological profiling indicates that berberine destroyed the structure of the cell walls, membrane integrity and further changed the cell morphology with concentration increased.ConclusionIn our study, berberine has excellent anti-MRSA activities and has synergistic antibacterial property when combined with clindamycin and rifamycin separately, and the mechanism of activities involves the destruction of cell wall and membrane.

Bacterial Cell Envelope Lysis and Hemotoxicity of Peptides Previously isolated From African Catfish, Clarias gariepinus

Background: The skin mucus layer of fish is endowed with biologics including, Antimicrobial peptides (AMPs) that offer a first line of defence against pathogens. Such peptides can either inhibit bacterial growth or completely kill the bacteria and hence are regarded as a viable alternative to traditional antibiotics, in addressing the ever-increasing incidences of antimicrobial resistance. However, one of the major hurdles to AMPs use is their poor haemolytic profile. As a result, a thorough evaluation of prospective AMPs’ bacterial cell membrane disruption and hemolytic potentials in the early phases of drug discovery is critical. The current study presented cell membrane destruction as well as hemo-compatibility of antimicrobial peptides previously isolated from skin mucus of African catfish, Clarias gariepinus. Methods: A previously isolated antimicrobial peptide in the skin mucus of African catfish, C. gariepinus were profiled using 15% Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE). The electrical conductivity and alkaline phosphatase assays were utilised to measure bacterial cell envelope lysis activity as a classical mode of action of the antimicrobial peptides. Afterwards, fresh Rabbit blood cells were then utilised for in vitro hemolytic assay. Results: The peptides were found to be about 5 kDa molecular weight with, ability to damage the bacterial cell envelope causing significant leakage in periplasmic alkaline phosphatase enzyme and cytoplasmic electrolytes. Even at the highest peptide extract concentration of 100 μg/mL, no significant hemolysis was observed on the fresh rabbit blood cells [3.63%;P&gt;.05], signifying their safety on normal mammalian cells. Conclusion: The findings of this study pointed out that antimicrobial peptides in skin mucus of C. gariepinus are potentially safe source of antimicrobial drug leads; however, further studies are still required to search for possibly maximum dose that is safe to host cells but still effective against infecting bacteria.

Coagulopathy and Thromboembolism in COVID-19: A Review

The emergence of the novel coronavirus, SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) has resulted in a major global pandemic posing various challenges to the worldwide health care systems. Clinical course of the infection, known as coronavirus disease of 2019 (COVID-19, ranges from mild subclinical disease to a life-threatening systemic illness. Common symptoms include a flu-like illness with fever and inflammation, and in severe cases pneumonia and systemic inflammation that results in morbidity and mortality. One of the complications of COVID-19 is its disruption of normal hemostasis resulting coagulopathy and thromboembolism. In this following review, we discuss present knowledge; summarize existing published information on the underlying mechanisms of action for COVID-19-associated coagulopathy; and propose algorithms for screening, management, and prevention of COVID-19 patients. Many at-risk COVID-19 patients develop coagulopathies that can broadly be labelled as venous thromboembolism (VTE). These coagulopathies may occur separately or in combination, and include pulmonary embolism (PE), deep vein thrombosis (DVT) and acute large vessel occlusion resulting in stroke, myocardial infarction, ischemic and systemic arterial events. Laboratorybased testing is mandatory in the case of severely infected COVID-19 patients for screening of their coagulation status. Based on recent data, a major elevation in the levels of the D-dimer is used as a predictor of the adverse outcomes of the disease. An imbalance between inflammation and coagulation may lead to a hypercoagulable state resulting in endothelial injury associated with a loss of dysregulation of fibrinolysis, excess thrombin generation, thrombi protective mechanisms, and thrombosis. Other involved mechanisms that may lead to an increased VTE risk, include the following: microvascular thrombosis, endothelial damage, leukocyte recruitment, systemic inflammation – the presence of the virus in endothelial cells, higher vascular permeability, destruction of cell membranes, platelet activation, and occlusion with ACE dysfunction, or even autoimmune mechanism. In all hospitalized COVID-19 patients, prophylaxis against thromboembolism is extremely important, especially in patients with elevated D-dimer levels and other coagulation abnormalities.

Peroxyl radical induced membrane instability of giant unilamellar vesicles and anti-lipooxidation protection

The present work is intended to investigate the morphological instability of lipid membrane induced by peroxyl radical (ROO•) and the underlying mechanism. To this end, the giant unilamellar vesicle (GUV) made from phosphatidylcholine was employed as a membrane model, and the azo compounds 2,2′-azobis(2,4-dimethylvaleronitrile) (AMVN) and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) were used as the precursors of ROO•. Upon mild pyrolysis, the GUV immobilized in agarose gel was followed by conventional optical microscopy in real time, and the morphological variation was quantified by the image heterogeneity, perimeter and area all as a function of time for up to an hour. Lipid oxidation initiated from lipid phase with AMVN and from aqueous phase with AAPH led to different types of morphological changes, i.e. membrane coarsening and vesicle deformation/budding, respectively. Based on the compositional analysis of lipid oxidation products, we propose that ROO• as the primary radical initiator is responsible for the morphological changes of the GUV-AMVN while both ROO• and RO• are responsible for the morphological changes of the GUV-AAPH system. Lipophilic β-carotene and amphipathic plant phenols as antioxidants are found to be able to stabilize the membrane integrity effectively, in corroboration with the proposed mechanisms for membrane destruction.

Bactericidal process and practicability for environmental water sterilization by solar-light-driven Bi2WO6-based photocatalyst

Pathogenic microorganism has always been a major threat to human health, which results in infectious diseases and even massive death. In the present study, the solar-light-driven photocatalyst Ag/Ag2O/BiPO4/Bi2WO6 was firstly used for water disinfection. The results showed the Ag/Ag2O/BiPO4/Bi2WO6 composite completely inactivated 7.40 log10 cfu/mL Escherichia coli within only 20 min under light irradiation. The inactivation mechanism was systematically investigated from the antioxidant enzymes, cell membrane, intracellular components and active species involved in the disinfection process. At the early stage of disinfection, the antioxidant system was initiated and increased enzyme activities to fight oxidative attack. Unfortunately, with accumulation of oxidative damage, the activities of antioxidant enzymes were suppressed, leading to deterioration of defense system. After destruction of defense system, cell membrane was destroyed gradually, monitored by K+ leakage and microscopic images. Furthermore, severe destruction of cell membrane led to leakage of nucleic acid and proteins, suggesting the irreversible death of bacteria. The photogenerated active species including superoxide radicals and holes played major roles in bactericidal process. In addition, the composite exhibited high adaptability for water disinfection at a wide range of environmental factors including light intensity, temperature, pH and humic acid. The slight release of Ag+ (<0.1 mg/L) and high stability of photocatalysts during successive disinfection experiments further implied its great potential for application. This work introduced an efficient solar-light-driven photocatalyst Ag/Ag2O/BiPO4/Bi2WO6, which exhibited a promising prospect for practical application, in hope of providing more useful information for water disinfection.