Gram-positive Bacterial Pathogens Research Articles

Genetics, Structure, and Function of Group A Streptococcal Pili.

Streptococcus pyogenes (Group A Streptococcus; GAS) is an exclusively human pathogen. This bacterial species is responsible for a large variety of infections, ranging from purulent but mostly self-limiting oropharynx/skin diseases to streptococcal sequelae, including glomerulonephritis and rheumatic fever, as well as life-threatening streptococcal toxic-shock syndrome. GAS displays a wide array of surface proteins, with antigenicity of the M protein and pili utilized for M- and T-serotyping, respectively. Since the discovery of GAS pili in 2005, their genetic features, including regulation of expression, and structural features, including assembly mechanisms and protein conformation, as well as their functional role in GAS pathogenesis have been intensively examined. Moreover, their potential as vaccine antigens has been studied in detail. Pilus biogenesis-related genes are located in a discrete section of the GAS genome encoding fibronectin and collagen binding proteins and trypsin-resistant antigens (FCT region). Based on the heterogeneity of genetic composition and DNA sequences, this region is currently classified into nine distinguishable forms. Pili and fibronectin-binding proteins encoded in the FCT region are known to be correlated with infection sites, such as the skin and throat, possibly contributing to tissue tropism. As also found for pili of other Gram-positive bacterial pathogens, GAS pilin proteins polymerize via isopeptide bonds, while intramolecular isopeptide bonds present in the pilin provide increased resistance to degradation by proteases. As supported by findings showing that the main subunit is primarily responsible for T-serotyping antigenicity, pilus functions and gene expression modes are divergent. GAS pili serve as adhesins for tonsillar tissues and keratinocyte cell lines. Of note, a minor subunit is considered to have a harpoon function by which covalent thioester bonds with host ligands are formed. Additionally, GAS pili participate in biofilm formation and evasion of the immune system in a serotype/strain-specific manner. These multiple functions highlight crucial roles of pili during the onset of GAS infection. This review summarizes the current state of the art regarding GAS pili, including a new mode of host-GAS interaction mediated by pili, along with insights into pilus expression in terms of tissue tropism.

Positional Isomers of Biphenyl Antimicrobial Peptidomimetic Amphiphiles.

Small-molecule antimicrobial peptidomimetic amphiphiles represent a promising class of novel antimicrobials with the potential for widespread therapeutic application. To investigate the role of spatial positioning for key hydrophobic and hydrophilic groups on the antimicrobial efficacy and selectivity, positional isomers of the lead biphenyl antimicrobial peptidomimetic compound 1 were synthesized and subjected to microbial growth inhibition and mammalian toxicity assays. Positional isomer 4 exhibited 4-8× increased efficacy against the pathogenic Gram-negative bacteria Pseudomonas aeruginosa and Escherichia coli (MIC = 2 μg/mL), while isomers 2, 3, and 7 exhibited a 4× increase in activity against Acinetobacter baumannii (MIC = 4 μg/mL). Changes in molecular shape had a significant impact on Gram-negative antibacterial efficacy and the resultant spectrum of activity, whereas all structural isomers exhibited significant efficacy (MIC = 0.25-8 μg/mL) against Gram-positive bacterial pathogens (e.g., methicillin-resistant Staphylococcus aureus, Streptococcus pneumoniae, and Enterococcus faecalis).

Coatable and Resistance-Proof Ionic Liquid for Pathogen Eradication.

Antibiotic-resistant bacteria infect close to 3 million people, and kill 35,000, each year in the United States. Ionic liquid (IL)-based antimicrobial agents have the potential to diversify our ever-diminishing antibiotic arsenal. Here, we describe an IL with potent submicromolar antimicrobial activity in vitro against clinically relevant Gram-negative and Gram-positive bacterial pathogens as well as anti-infective activity in a mouse model. The IL kills pathogenic bacteria such as Acinetobacter baumannii, Salmonella enterica, and Escherichia coli by disrupting their outer membrane and does not select for bacterial resistance. We show incorporation of our IL into surface coatings to generate a type of antibiofilm material. The IL-loaded ionogel surfaces demonstrate high-antimicrobial and antifouling activity by killing bacteria in both static and dynamic tests. Our IL-based antibiofilm surfaces are low-cost and easy to manufacture, can be formed on glass, latex, plastic, and metal surfaces, such as catheters and other medical devices where high local concentrations of antimicrobials are needed, and may have applications in other clinical and industrial settings.

Heterologous production of a cyanobacterial bacteriocin with potent antibacterial activity

Abstract With regard to the emerging health threat by antibiotic resistant bacteria, bacteriocins are considered as a promising way to overcome this urgent problem. In this work, a hitherto unknown bacteriocin from the terrestrial cyanobacterium Chroococcidiopsis cubana was heterologously expressed in Escherichia coli, purified to homogeneity and tested for activity against several bacteria and one yeast species. The compound showed potent bacteriolytic activity against several Gram-positive bacteria and slight activity against one Gram-negative strain. The bacteriocin had no cytotoxic impact on mouse neuroblastoma N2a cells, indicating its potential for treatment against Gram-positive bacterial pathogens in human diseases.

Reverse vaccinology and subtractive genomics approaches for identifying common therapeutics against Mycobacterium leprae and Mycobacterium lepromatosis.

Background Mycobacterium leprae and Mycobacterium lepromatosis are gram-positive bacterial pathogens and the causative agents of leprosy in humans across the world. The elimination of leprosy cannot be achieved by multidrug therapy alone, and highlights the need for new tools and drugs to prevent the emergence of new resistant strains.Methods In this study, our contribution includes the prediction of vaccine targets and new putative drugs against leprosy, using reverse vaccinology and subtractive genomics. Six strains of Mycobacterium leprae and Mycobacterium lepromatosis (4 and 2 strains, respectively) were used for comparison taking Mycobacterium leprae strain TN as the reference genome. Briefly, we used a combined reverse vaccinology and subtractive genomics approach.Results As a result, we identified 12 common putative antigenic proteins as vaccine targets and three common drug targets against Mycobacterium leprae and Mycobacterium lepromatosis. Furthermore, the docking analysis using 28 natural compounds with three drug targets was done.ConclusionsThe bis-naphthoquinone compound Diospyrin (CID 308140) obtained from indigenous plant Diospyros spp. showed the most favored binding affinity against predicted drug targets, which can be a candidate therapeutic target in the future against leprosy.

1566. In vitro Activities of Ceftaroline and Comparator Agents against Gram-positive Bacterial Pathogens Causing Blood Stream Infections in a Global Population: ATLAS Surveillance Program 2012-2018

BackgroundTypical gram-positive organisms causing bloodstream infections (BSI) include Staphylococcus aureus (methicillin-susceptible [MSSA] and -nonsusceptible [MRSA]), coagulase negative staphylococci, Streptococcus pneumoniae and beta hemolytic streptococci. The parenteral cephem ceftaroline fosamil is approved for treatment of patients with community-acquired bacterial pneumonia caused by S. pneumoniae (including cases with concurrent bacteremia), MSSA, Haemophilus influenzae, and some species of Enterobacterales. Limited data have been published on the in vitro activity of ceftaroline against recent gram-positive clinical isolates known to be frequent bacterial causes of blood stream infections.MethodsStandard CLSI broth microdilution MIC determinations (M07) were performed with ceftaroline and comparator agents. MICs were interpreted using 2020 CLSI MIC breakpoints. Clinically relevant, non-duplicate, isolates cultured from blood by clinical laboratories in 2012-2018 were tested by the ATLAS (Antimicrobial Testing Leadership and Surveillance) program central laboratory (IHMA, Inc., Schaumburg, IL, USA). In total, 10,998 non-duplicate isolates of S. aureus, S. epidermidis, S. pneumoniae and beta hemolytic streptococci from BSI collected between 2012 and 2018 were tested. Isolates came from (n/%): Asia/South Pacific (1,739/15.8%), Europe (5,448/49.5%), Latin America (1,805/16.4%), MidEast/Africa (861/7.8%), and North America (1,145/10.4%).ResultsCeftaroline and comparator agent activities are summarized in the following table.Table ConclusionGreater than 98% of S. pneumoniae, S. epidermidis, beta-hemolytic streptococci and MSSA isolates included in a 2012-2018 collection of gram-positive blood stream pathogens were susceptible to ceftaroline. 91.4% of MRSA were susceptible, and 8.6% isolates categorized as susceptible-dose dependent (MIC, 2-4 ug/mL); two isolates (one each from Thailand and S. Korea) were resistant to ceftaroline (MIC >4 ug/mL). Ceftaroline continues to demonstrate potent in vitro activity against clinically relevant pathogens associated with BSI.Disclosures Greg Stone, PhD, AztraZeneca (Shareholder, Former Employee)Pfizer, Inc. (Employee) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Consultant)Shionogi & Co., Ltd. (Independent Contractor)

Biofilm Formation on Breast Implant Surfaces by Major Gram-Positive Bacterial Pathogens.

Bacterial biofilm on surfaces of mammary implants is a predisposing factor for several outcomes. Because Gram-positive bacteria are potential agents of biomaterial-associated infections (BAIs), their abilities to form biofilm on breast implants should be elucidated. The aim of this study was to evaluate biofilm formation on different mammary prosthesis surfaces by major Gram-positive bacterial pathogens involved in BAIs. We initially evaluated biofilm formation on polystyrene plates with and without fibrinogen or collagen for 1 reference strain and 1 clinical isolate of Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pyogenes. We also tested the ability of clinical isolates to form biofilm on 4 different implant surfaces: polyurethane foam and smooth, microtextured, and standard textured silicone. Biofilm structure and cell viability were observed by scanning electron microscopy and confocal laser scanning microscopy. All strains showed strong biofilm formation on polystyrene. After fibrinogen or collagen treatment, biofilm formation varied. With fibrinogen, reference strains of S. aureus and S. pyogenes increased biofilm formation (P < 0.05). Reference strains of all species and the clinical isolate of S. pyogenes increased biofilm formation after collagen treatment (P < 0.05). In general, S. aureus showed higher capacity to produce biofilm. Scanning electron microscopy showed that biofilm attached to all surfaces tested, with the presence of extracellular polymeric substances and voids. Viable cells were more frequent for E. faecalis and S. pyogenes. All species produced biofilm on all prosthesis surfaces and under different conditions. Micrographies indicated thicker bacterial biofilm formation on microtextured and/or standard textured silicone by all species, except E. faecalis.

Beta-Haemolytic Group A, C and G Streptococcal Infections in Southern Hungary: A 10-Year Population-Based Retrospective Survey (2008-2017) and a Review of the Literature.

IntroductionPyogenic β-hemolytic streptococci (including Group A, C and G Streptococcus) are some of the most important Gram-positive bacterial pathogens in human medicine. Although effective therapy is available, invasive streptococcal infections are associated with a significant disease burden.MethodsIn this retrospective study, the epidemiological characteristics of invasive Group A (iGAS) and Group C and G (iGCGS) streptococci, along with tonsillo-pharyngitis-causing pGAS and pGCGS infections, were assessed in Southern Hungary. A total of 1554 cases of streptococcal tonsillo-pharyngitis infections (26.5–44.1/100,000 persons, pGAS: 95.5%; n=1484) and 1104 cases of invasive streptococcal infections were detected (12.5–31.4/100,000 persons, iGAS: 77.9%; n=861).ResultsThe average age of the affected patients in the various groups were the following: pGAS: 13.2±13.1 years, pGCGS: 21.0±15.0 years (p=0.039), iGAS: 49.1±12.8 years, iGCGS: 58.7±18.5 years (p>0.05). iGAS isolates originated from abscesses (47.1%), blood culture samples (24.1%), surgical samples (16.7%), biopsies (4.6%), pleural fluid (3.5%), pus (2.0%), synovial fluid (1.3%) and cerebrospinal fluid samples (0.7%). In contrast, iGCGS isolates mainly originated from blood culture samples (53.8%), abscesses (22.9%), surgical samples (12.3%), synovial fluid (5.1%), pleural fluid (3.7%), pus (1.8%) and cerebrospinal fluid samples (0.4%). All respective isolates were susceptible to benzyl-penicillin; overall resistance levels for erythromycin (10.5% for GAS, 21.4% for GCGS) and clindamycin (9.2% for GAS, 17.2% for GCGS) were significantly higher in GCGS isolates, while resistance levels for norfloxacin were higher in GAS isolates (13.5% for GAS, 6.9% for GCGS).ConclusionThe rates of resistance to macrolides and clindamycin are a cause for concern (especially among GCGS isolates); however, resistance levels are still relatively low, compared to Southern European countries.

A diverse global fungal library for drug discovery.

BackgroundSecondary fungal metabolites are important sources for new drugs against infectious diseases and cancers.MethodsTo obtain a library with enough diversity, we collected about 2,395 soil samples and 2,324 plant samples from 36 regions in Africa, Asia, and North America. The collection areas covered various climate zones in the world. We examined the usability of the global fungal extract library (GFEL) against parasitic malaria transmission, Gram-positive and negative bacterial pathogens, and leukemia cells.ResultsNearly ten thousand fungal strains were isolated. Sequences of nuclear ribosomal internal transcribed spacer (ITS) from 40 randomly selected strains showed that over 80% were unique. Screening GFEL, we found that the fungal extract from Penicillium thomii was able to block Plasmodium falciparum transmission to Anopheles gambiae, and the fungal extract from Tolypocladium album was able to kill myelogenous leukemia cell line K562. We also identified a set of candidate fungal extracts against bacterial pathogens.

The Role of Gram-Positive Surface Proteins in Bacterial Niche- and Host-Specialization.

Gram-positive bacterial pathogens have an array of proteins on their cell surface that mediate interactions with the host environment. In particular, bacterial cell wall-associated (CWA) proteins play key roles in both colonization and pathogenesis. Furthermore, some CWA proteins promote specialization for host-species or mediate colonization of specific anatomical niches within a host. In this mini review, we provide examples of the many ways by which major pathogens, such as Staphylococci, Streptococci and Listeria monocytogenes, utilize CWA proteins for both host- and niche-specialization. We describe different biological mechanisms mediated by CWA proteins including: the acquisition of iron from hemoglobin in the bloodstream, adherence to and invasion of host cells, and innate immune evasion through binding to the plasma proteins fibrinogen, immunoglobulin G, and complement. We also discuss the limitations of using animal models for understanding the role of specific CWA proteins in host-specialization and how transformative technologies, such as CRISPR-Cas, offer tremendous potential for developing transgenic models that simulate the host environment of interest. Improved understanding of the role of CWA proteins in niche- or host-specificity will allow the design of new therapeutic approaches which target key host–pathogen interactions underpinning Gram-positive bacterial infections.

Synthesis of biocompatible chitosan decorated silver nanoparticles biocomposites for enhanced antimicrobial and anticancer property

Numerous studies investigated the biosynthesis of silver nanoparticles (AgNPs); however, there is a large gap for the ideal time-consuming process and their cytotoxicity. Herein, for the first time, rapid AgNPs was synthesized in a short time span, using Piper betle leaf (PBL) extract by applying microwave exposure. PB-AgNPs antibacterial activity and cell compatibility were enhanced by capping with chitosan (CS@PB-AgNPs). The synthesized nanoparticles were characterized by bioanalytical techniques. PB-AgNPs expressed significant antibacterial activity against Gram-positive and Gram-negative bacterial pathogens, while hybrid CS@PB-AgNPs presented the enhanced bactericidal activity. In addition, PB-AgNPs exhibited IC50 value of 140 μg/mL against RAW 264.7 macrophages and 100 μg/mL against lung cancer cells while, CS capping reduced its toxicity at IC50 values of 400 μg/mL and 180 μg/mL respectively were affirmed by MTT, apoptosis and DNA damage detection. Overall it was demonstrated that CS capping could be a phenomenal finding to improve the biomedical potential of AgNPs.

Wound-healing potential of curcumin loaded lignin nanoparticles

The emergence of new material platforms, focused on nanotechnology, have resulted in a growing interest in their application to healing skin wounds. The skin forms an effective barrier against the external environment and consequently, rapid healing of wound tissue after injury is essential. Curcumin (diferuloylmethane) is a promising small molecule for the treatment of wounds based on its wound-healing activity and antioxidant and anti-inflammatory properties. However, its therapeutic application is limited by the poor skin permeability and bioavailability due to its poor solubility and low stability. Herein, curcumin loaded LNPs was prepared and characterized for their wound healing activity. Cytotoxicity assays indicated that curcumin-free and loaded nanoparticles were biocompatible with skin keratinocytes with no cytotoxic effects, suggesting that they did not interfere with cell proliferation during wound healing. Curcumin loaded LNPs exhibited potent in vitro antibacterial activity against gram-positive bacterial pathogens, particularly against Staphylococcus aureus, the most common wound bacterium. Fibroblast cell migration was observed using a scratch assay; upon treatment with curcumin loaded LNPs, wounded keratinocytes exhibited increased cell migration, which is a key feature of wound healing. The in vivo results showed that wounded rats treated with curcumin loaded LNPs exhibited enhanced dermal wound closure compared with the untreated control. After 12 days, the wounds treated with curcumin loaded LNPs achieved nearly full wound contraction compared with the untreated control, which had a wound size reduction of approximately 43%. Curcumin-loaded LNPs treated wounds showed advanced granulation tissue formation, characterized by greater collagen deposition. They also had lower myeloperoxidase activity, which is indicative of less inflammatory infiltration. Lower expression of matrix metalloproteinases (MMPs), especially MMP9, was characteristic of wounds treated with curcumin loaded LNPs. Overall, the results from this study highlight the advantages of using lignin as a nanocarrier to accelerate wound healing.

Expression profile of kalliklectin, a soluble-type mannose receptor, during embryogenesis and early larval development in fugu (Takifugu rubripes)

Kalliklectin is a unique fish-specific lectin, whose sequence is similar to the heavy chain of mammalian plasma kallikrein and coagulation factor XI. In this study, we aimed to evaluate dynamic expression profiles of the lectin gene, during early developmental stages, in fugu, Takifugu rubripes. Reverse transcription-polymerase chain reaction (RT-PCR) showed that the kalliklectin gene was not expressed until 14 h post-fertilization (hpf), while the mRNA was detected after 30 hpf. In real-time quantitative PCR (qPCR), the gene was first expressed at 10.5 hpf; then, the expression level increased with a peak at 30 hpf and then gradually decreased. On the other hand, western blotting with specific antibody detected the lectin protein at all tested stages, including the unfertilized egg, which suggests that the lectin detected in the early stages was a maternal factor. Immunohistochemistry demonstrated that kalliklectin was localized at the basement membranes of the newly hatched larvae, while the lectin was widely detected in epidermal cells in larva at 5 dph. A 40-kDa lectin was partially purified from unfertilized eggs using mannose-affinity chromatography, and the lectin was determined as kalliklectin by liquid chromatography with quadrupole time-of-flight tandem mass spectrometry (LC/Q-TOF-MS) analysis, which indicated that the lectin is functional in the eggs. The egg lectin can bind to Gram-positive bacterial pathogens of fish, such as Lactococcus garvieae and Streptococcus iniae. We conclude that fugu kalliklectin might be an important immunocomponent, transferred from mother to offspring.

Infections in children with left ventricular assist device.

There are limited data about pediatric left ventricular assist device (VAD) infections in developing countries. This study aimed to investigate device postimplantation infectious complications and their pathogenic profile. Data were analyzed from patient charts involving 27 patients with dilated cardiomyopathy who underwent left VAD implantation at a leading tertiary care center in Turkey. The study included 17 boys and ten girls with a median age of 12.22years (range 17months to 18years). Nineteen patients were diagnosed with idiopathic, and three were diagnosed with familial dilated cardiomyopathy. Twenty-two out of 27 subjects (%81.48) developed 80 infection episodes in total. The most common type of left VAD-specific infection was the exit site of the driveline. Infected patients with left VAD had a significantly prolonged hospitalization compared with the patients without infection (P=.014). Infection-induced pediatric intensive care unit (ICU) admission was higher in patients with fungal infection(P=.023). Gram-positive staphylococci were the most commonly isolated bacterial pathogens, followed by Gram-negative bacteria. Five patients developed fungal infections. None of the fungal infection patients underwent transplantation(P=.035). Seven deaths occurred in our study group. All deaths were in the infected group. Mortality was associated with the presence of multidrug-resistant Gram-negative bacterial infections (P=.015), an increased number of infection episodes (P=.003), and hospitalization due to infection (P=.003). Ventricular assist device-related infections were frequent among our study patients. The predominantly isolated agents were Gram-positive bacterial pathogens. However, the emergence of relatively high rate of Gram-negative bacterial and fungal infections was associated with mortality before the transplantation. Establishing local programs for surveillance data, controlling for infection rates, and antibiotic stewardship are essential to reduce mortality of VAD patients in developing countries.

Immunological and antibiofilm property of haemocyanin purified from grooved tiger shrimp (Penaeus semisulcatus): An in vitro and in silico approach

Haemocyanin (Hc) is a non-specific innate immune protein present in the haemolymph of arthropods and molluscs. In the current study, we characterized the structural and immunological properties of Hc from grooved tiger shrimp, Penaeus semisulcatus. Hc was isolated from the haemolymph of P. semisulcatus by gel filtration column chromatography using Sephadex G-100. High-performance liquid chromatography of the purified Hc emerged as a single peak through a retention time of 3.3 min demonstrating the homogeneity nature of the protein. X-ray diffraction analysis revealed a distinct peak at 31.7° indicating the crystalline character of the purified Hc. Circular dichroism spectra of the purified Hc displayed negative ellipticity bands close to 225 nm and 208 nm representing β-sheet secondary structure. The purified Hc agglutinated sheep RBCs, yeast Saccharomyces cerevisiae and fungal Candida albicans. In addition, the purified Hc displayed antibacterial activity against Gram-positive bacteria (Bacillus thuringiensis and Bacillus pumilis) and Gram-negative bacteria (Vibrio parahaemolyticus and Vibrio alginolyticus) with a minimal inhibitory concentration of 50 μg/ml. Antibiofilm activity revealed the potential of purified Hc to inhibit biofilm formation of both Gram-positive and Gram-negative bacterial pathogens. Furthermore, live/dead staining of biofilms demonstrated the reduced viability of bacterial cells after exposure to the purified Hc. In silico molecular modeling was carried out using the sequence of Hc from SwissProt and molecular docking was performed with the cell surface components found in Gram-positive and Gram-negative bacteria. Overall our study demonstrates the involvement of Hc in the native immune reaction of P. semisulcatus by eliciting pathogen recognition. Thus, Hc could enhance disease resistance against pathogenic infection in shrimp aquaculture.

Resistance of Gram-Positive Bacteria to Current Antibacterial Agents and Overcoming Approaches.

The discovery of antibiotics has created a turning point in medical interventions to pathogenic infections, but unfortunately, each discovery was consistently followed by the emergence of resistance. The rise of multidrug-resistant bacteria has generated a great challenge to treat infections caused by bacteria with the available antibiotics. Today, research is active in finding new treatments for multidrug-resistant pathogens. In a step to guide the efforts, the WHO has published a list of the most dangerous bacteria that are resistant to current treatments and requires the development of new antibiotics for combating the resistance. Among the list are various Gram-positive bacteria that are responsible for serious healthcare and community-associated infections. Methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecium, and drug-resistant Streptococcus pneumoniae are of particular concern. The resistance of bacteria is an evolving phenomenon that arises from genetic mutations and/or acquired genomes. Thus, antimicrobial resistance demands continuous efforts to create strategies to combat this problem and optimize the use of antibiotics. This article aims to provide a review of the most critical resistant Gram-positive bacterial pathogens, their mechanisms of resistance, and the new treatments and approaches reported to circumvent this problem.

Characterising lipoteichoic acid as an in vitro model of acute neuroinflammation

Toll-like receptor 2 (TLR2) is a primary sensor for pathogens, including those derived from gram-positive bacteria. It can also mediate the effects of endogenous inflammatory signals such as β-amyloid peptide (Aβ), thus promoting the microglial activation and subsequent neuronal dysfunction, characteristic of chronic neuroinflammatory conditions. More recently, a role for TLR2 has been proposed in the pathogenesis of disorders associated with acute inflammation, including anxiety and depression. The current study aims to characterise the acute effects of the TLR2 agonist lipoteichoic acid (LTA) on microglial activation and neuronal integrity, and to evaluate the influence of LTA exposure on sensitivity to the inflammation and neuronal dysfunction associated with Aβ. Using BV2 and N2a cells as an in vitro model, we highlight that acute exposure to LTA robustly promotes inflammatory cytokine and nitric oxide (NO) production in microglia but also in neurons, similar to that reported under longer-term and chronic inflammatory conditions. Moreover, we find that exposure to LTA can enhance sensitivity to subthreshold Aβ, promoting an ‘M1′-like phenotype in microglia and provoking dysregulation of neuronal activity in acute hippocampal slices. Anti-inflammatory agents, including mimetics of brain-derived neurotrophic factor (BDNF), have proven effective at alleviating chronic neuroinflammatory complications. We further examined the effects of 7,8,3-trihydroxyflavone (7,8,3-THF), a small-molecule TrkB agonist, on LTA-induced microglial activation. We report that 7,8,3-THF can significantly ameliorate interleukin (IL)-6 and NO production in LTA-stimulated BV2 cells. Taken together, our findings offer support for exploration of TLR2 as a potential target for therapeutic intervention into acute neuroinflammatory conditions. Moreover we propose that exposure to gram-positive bacterial pathogens may promote sensitivity to the inflammatory changes characteristic of the aged brain.

Synthesis, Characterization and Antimicrobial Evaluation of Piyar Gum-Induced Silver Nanoparticles

Buchanania lanzan gum commonly known as char, achar, piyar and chironji is a naturally occurring water-soluble, edible polysaccharide derived from the bark of Buchanania lanzan Spreng. Silver nanoparticles have been synthesized using Buchanania lanzan gum exudates adopting green synthesis methodology and characterized by UV–Vis, Fourier transform infrared spectroscopy, zeta potential and particle size analysis, scanning electron microscopy, transmission electron microscopy and atomic force microscopy confirming the synthesis of AgNPs. The synthesized piyar gum-induced AgNPs are spherical in shape, small enough in size (14.74–19.86 nm) and noncytotoxic. Evaluation of bactericidal activity of synthesized piyar gum-induced AgNPs against 17 strains of 14 Gram-negative and Gram-positive bacterial pathogens, using agar well diffusion method, exhibited strong bactericidal activity against Gram-negative bacterial pathogens. The minimum inhibitory concentration against two Gram-negative bacterial strains, i.e., Escherichia coli and Avibacterium avium, was found to be 0.52 µg/mL and 0.53 µg/mL, respectively, which was at par with that of positive control (0.5 mM silver nitrate solution).

Antibacterial Potential and Apoptosis Induction by Pigments from the Endophyte Burkholderia sp. WYAT7.

Pigment from the endophyte Burkholderia sp. WYAT7 isolated from the medicinal plant Artemisia nilagirica (Clarke) Pamp. was extracted. The antibacterial efficacy of the crude pigment Y was assessed as a source of antibiotic against both Gram-positive and Gram-negative bacterial pathogens. The pigment Y exhibited a significant level of antibacterial activity against the tested pathogens Salmonella typhi (MTCC 733), Staphylococcus aureus (MTCC 1430), Pseudomonas aeruginosa (MTCC 2453), Klebsiella pneumoniae (MTCC 432), Escherichia coli (MTCC 1610), Salmonella paratyphi (3220), Bacillus subtilis (441) and Acinetobacter baumannii (12,889). The minimum inhibitory concentration of crude pigment extract Y for most of the bacterial pathogens tested was below or equal to 0.25 µg/mL and the minimum bactericidal concentration was below or equal to 0.5 µg/mL. In the cytotoxicity evaluation, crude pigment Y exhibited less toxicity toward normal cells lines (L929). Crude pigment extract Y also showed powerful anticancer activity toward melanoma cancer cells (A375). The IC50 value obtained was 68.08 µg/mL. Acridine orange (AO) and ethidium bromide (EB) double staining of cells treated with the pigment helped in the morphological assessment of nuclear condensation, apoptotic bodies and live cells. The DNA fragmentation analysis and caspase-9 quantification in the pigment-treated A375 cells determined the apoptosis activity mediated by the crude pigment extract Y. The compounds in the crude pigment extract Y was identified by HR-LCMS analysis. Further studies on the active compounds can lead to a rise in new drugs for cancer treatment and also against rising antibacterial resistant pathogens.

Interactions of Tea-Derived Catechin Gallates with Bacterial Pathogens.

Green tea-derived galloylated catechins have weak direct antibacterial activity against both Gram-positive and Gram-negative bacterial pathogens and are able to phenotypically transform, at moderate concentrations, methicillin-resistant Staphylococcus aureus (MRSA) clonal pathogens from full β-lactam resistance (minimum inhibitory concentration 256–512 mg/L) to complete susceptibility (~1 mg/L). Reversible conversion to susceptibility follows intercalation of these compounds into the bacterial cytoplasmic membrane, eliciting dispersal of the proteins associated with continued cell wall peptidoglycan synthesis in the presence of β-lactam antibiotics. The molecules penetrate deep within the hydrophobic core of the lipid palisade to force a reconfiguration of cytoplasmic membrane architecture. The catechin gallate-induced staphylococcal phenotype is complex, reflecting perturbation of an essential bacterial organelle, and includes prevention and inhibition of biofilm formation, disruption of secretion of virulence-related proteins, dissipation of halotolerance, cell wall thickening and cell aggregation and poor separation of daughter cells during cell division. These features are associated with the reduction of capacity of potential pathogens to cause lethal, difficult-to-treat infections and could, in combination with β-lactam agents that have lost therapeutic efficacy due to the emergence of antibiotic resistance, form the basis of a new approach to the treatment of staphylococcal infections.