Brianna Dalesandro

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Burkholderia thailandensis outer membrane vesicles exert antimicrobial activity against drug-resistant and competitor microbial species.

J Microbiol. 2020 Apr 11;:

Authors: Wang Y, Hoffmann JP, Chou CW, Höner Zu Bentrup K, Fuselier JA, Bitoun JP, Wimley WC, Morici LA

Abstract
Gram-negative bacteria secrete outer membrane vesicles (OMVs) that play critical roles in intraspecies, interspecies, and bacteria-environment interactions. Some OMVs, such as those produced by Pseudomonas aeruginosa, have previously been shown to possess antimicrobial activity against competitor species. In the current study, we demonstrate that OMVs from Burkholderia thailandensis inhibit the growth of drug-sensitive and drug-resistant bacteria and fungi. We show that a number of antimicrobial compounds, including peptidoglycan hydrolases, 4-hydroxy-3-methyl-2-(2-non-enyl)-quinoline (HMNQ) and long-chain rhamnolipid are present in or tightly associate with B. thailandensis OMVs. Furthermore, we demonstrate that HMNQ and rhamnolipid possess antimicrobial and antibiofilm properties against methicillin-resistant Staphylococcus aureus (MRSA). These findings indicate that B. thailandensis secretes antimicrobial OMVs that may impart a survival advantage by eliminating competition. In addition, bacterial OMVs may represent an untapped resource of novel therapeutics effective against bio-film-forming and multidrug-resistant organisms.

PMID: 32281050 [PubMed - as supplied by publisher]

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Sodium, hypertension, and the gut: does the gut microbiota go salty?

Am J Physiol Heart Circ Physiol. 2019 12 01;317(6):H1173-H1182

Authors: Smiljanec K, Lennon SL

Abstract
Recent evidence suggests that the gut microbiota contributes to the pathogenesis of hypertension (HTN). The gut microbiota is a highly dynamic organ mediating numerous physiological functions, which can be influenced by external factors such as diet. In particular, a major modifiable risk factor for HTN is dietary sodium intake. Sodium consumption in the United States is significantly greater than that recommended by the federal government and organizations such as the American Heart Association. Because of the emerging connection between the gut microbiota and HTN, the interaction between dietary sodium and gut microbiota has sparked interest. High-sodium diets promote local and systemic tissue inflammation and impair intestinal anatomy compared with low sodium intake in both human and animal studies. It is biologically plausible that the gut microbiota mediates the inflammatory response, as it is in constant interaction with the immune system and is necessary for proper maturation of immune cells. Recent rodent data demonstrate that dietary sodium disrupts gut microbial homeostasis as gut microbiota composition shifts with dietary sodium manipulation. In this review, we will focus on gut microbiota activity in HTN and the influence of high dietary sodium intake with an emphasis on the immune system, bacterial metabolites, and the circadian clock.

PMID: 31585045 [PubMed - indexed for MEDLINE]

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Clofazimine Reduces Survival of Salmonella enterica in Macrophages and Mice.

ACS Infect Dis. 2020 Apr 09;:

Authors: Nagy TA, Crooks AL, Quintana JL, Detweiler CS

Abstract
Drug resistant pathogens are on the rise and new treatments are needed for bacterial infections. Efforts toward antimicrobial discovery typically identify compounds that prevent bacterial growth in microbiological media. However, the microenvironments to which pathogens are exposed during infection differ from rich media and alter the biology of the pathogen. We and others have therefore developed screening platforms that identify compounds that disrupt pathogen growth within cultured mammalian cells. Our platform focuses on Gram-negative bacterial pathogens, which are of particular clinical concern. We screened a panel of 707 drugs to identify those with efficacy against Salmonella enterica Typhimurium growth within macrophages. One of the drugs identified, clofazimine (CFZ), is an antibiotic used to treat mycobacterial infections that is not recognized for potency against Gram-negative bacteria. We demonstrated that in macrophages CFZ enabled the killing of S. Typhimurium at single digit micromolar concentrations, and in mice CFZ reduced tissue colonization. We confirmed that CFZ does not inhibit the growth of S. Typhimurium and E. coli in standard microbiological media. However, CFZ prevents bacterial replication under conditions consistent with the microenvironment of macrophage phagosomes, in which S. Typhimurium resides during infection: low pH, low magnesium and phosphate, and the presence of certain cationic antimicrobial peptides. These observations suggest that in macrophages and mice the efficacy of CFZ against S. Typhimurium is facilitated by multiple aspects of soluble innate immunity. Thus, systematic screens of existing drugs for infection-based potency is likely to identify unexpected opportunities for repurposing drugs to treat difficult pathogens.

PMID: 32272013 [PubMed - as supplied by publisher]

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Recent trends and advances in microbe-based drug delivery systems.

Daru. 2019 Dec;27(2):799-809

Authors: Shende P, Basarkar V

Abstract
Since more than a decade, pharmaceutical researchers endeavor to develop an effective, safe and target-specific drug delivery system to potentiate the therapeutic actions and reduce the side effects. The conventional drug delivery systems (DDSs) show the improvement in the lifestyle of the patients suffering from non-communicable diseases, autoimmune diseases but sometimes, drug resistance developed during the treatment is a major concern for clinicians to find an alternative and more advanced transport systems. Advancements in drug delivery facilitate the development of active carrier for targeted action with improved pharmacokinetic behavior. This review article focuses on microbe-based drug delivery systems to provide safe, non-toxic, site-specific targeted action with lesser side effects. Pharmaceutical researchers play a vital part in microbe-based drug delivery systems as a therapeutic agent and carrier. The properties of microorganisms like self-propulsion, in-situ production of therapeutics, penetration into the tumor cells, increase in immunity, etc. are of interest for development of highly effective delivery carrier. Lactococcus lactis is therapeutically helpful in Inflammatory Bowel Disease (IBD) and is under investigation of phase I clinical trial. Moreover, bacteria, anti-cancer oncolytic viruses, viral vectors (gene therapy) and viral immunotherapy are the attractive areas of biotechnological research. Virus acts as a distinctive candidate for imaging of tumor and accumulation of active in tumor. Graphical abstract Classification of microbe-based drug delivery system.

PMID: 31376116 [PubMed - indexed for MEDLINE]

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Bacterial Membrane Vesicles as Mediators of Microbe - Microbe and Microbe - Host Community Interactions.

Front Microbiol. 2020;11:432

Authors: Caruana JC, Walper SA

Abstract
Bacterial membrane vesicles are proteoliposomal nanoparticles produced by both Gram-negative and Gram-positive bacteria. As they originate from the outer surface of the bacteria, their composition and content is generally similar to the parent bacterium's membrane and cytoplasm. However, there is ample evidence that preferential packaging of proteins, metabolites, and toxins into vesicles does occur. Incorporation into vesicles imparts a number of benefits to the cargo, including protection from degradation by other bacteria, the host organism, or environmental factors, maintenance of a favorable microenvironment for enzymatic activity, and increased potential for long-distance movement. This enables vesicles to serve specialized functions tailored to changing or challenging environments, particularly in regard to microbial community interactions including quorum sensing, biofilm formation, antibiotic resistance, antimicrobial peptide expression and deployment, and nutrient acquisition. Additionally, based on their contents, vesicles play crucial roles in host-microbe interactions as carriers of virulence factors and other modulators of host cell function. Here, we discuss recent advances in our understanding of how vesicles function as signals both within microbial communities and between pathogenic or commensal microbes and their mammalian hosts. We also highlight a few areas that are currently ripe for additional research, including the mechanisms of selective cargo packaging into membrane vesicles and of cargo processing once it enters mammalian host cells, the function of vesicles in transfer of nucleic acids among bacteria, and the possibility of engineering commensal bacteria to deliver cargo of interest to mammalian hosts in a controlled manner.

PMID: 32265873 [PubMed]

Nature, Published online: 06 April 2020; doi:10.1038/d41586-020-01053-w

Examine the shaky evidence for the efficacy of a decades-old antimalarial against coronavirus. Plus: Canada begins the world’s largest clinical trial of survivors’ blood to treat COVID-19, and celebrating the life of astrophysicist Margaret Burbidge, who traced the origin of everything to the hearts of stars.

Nature, Published online: 09 April 2020; doi:10.1038/s41586-020-2223-y

Structure of M^pro from COVID-19 virus and discovery of its inhibitors

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Deployment of convalescent plasma for the prevention and treatment of COVID-19.

J Clin Invest. 2020 Apr 07;:

Authors: Bloch EM, Shoham S, Casadevall A, Sachais BS, Shaz B, Winters JL, van Buskirk C, Grossman BJ, Joyner M, Henderson JP, Pekosz A, Lau B, Wesolowski A, Katz L, Shan H, Auwaerter PG, Thomas D, Sullivan DJ, Paneth N, Gehrie E, Spitalnik S, Hod E, Pollack L, Nicholson WT, Pirofski LA, Bailey JA, Tobian AA

Abstract
Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the cause of coronavirus disease (COVID-19), has spurred a global health crisis. To date, there are no proven options for prophylaxis for those who have been exposed to SARS-CoV-2, nor therapy for those who develop COVID-19. Immune (i.e. "convalescent") plasma refers to plasma that is collected from individuals, following resolution of infection and development of antibodies. Passive antibody administration through transfusion of convalescent plasma may offer the only short-term strategy to confer immediate immunity to susceptible individuals. There are numerous examples, where convalescent plasma has been used successfully as post-exposure prophylaxis and/or treatment of infectious diseases, including other outbreaks of coronaviruses (e.g., SARS-1, Middle East Respiratory Syndrome [MERS]). Convalescent plasma has also been used in the COVID-19 pandemic; limited data from China suggest clinical benefit, including radiological resolution, reduction in viral loads and improved survival. Globally, blood centers have robust infrastructure to undertake collections and construct inventories of convalescent plasma to meet the growing demand. Nonetheless, there are nuanced challenges, both regulatory and logistical, spanning donor eligibility, donor recruitment, collections and transfusion itself. Data from rigorously controlled clinical trials of convalescent plasma are also few, underscoring the need to evaluate its use objectively for a range of indications (e.g., prevention vs treatment) and patient populations (e.g., age, comorbid disease). We provide an overview of convalescent plasma, from evidence of benefit, regulatory considerations, logistical work flow and proposed clinical trials, as scale up is brought underway to mobilize this critical resource.  .

PMID: 32254064 [PubMed - as supplied by publisher]

Nature Communications, Published online: 08 April 2020; doi:10.1038/s41467-020-15508-1

The role microbes play in human health and the ability of synthetic biology to engineer microbial properties opens up new ways of treating disease. In this perspective, the authors describe the design and development of these living therapeutics.

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Modified bacterial outer membrane vesicles induce autoantibodies for tumor therapy.

Acta Biomater. 2020 Apr 03;:

Authors: Huang W, Shu C, Hua L, Zhao Y, Xie H, Qi J, Gao F, Gao R, Chen Y, Zhang Q, Li W, Yuan M, Ye C, Ma Y

Abstract
Using monoclonal antibodies to block tumor angiogenesis has yielded effective antitumor effects. However, this treatment method has long cycles and is very expensive; therefore, its long-term and extensive application is limited. In this study, we developed a nanovaccine using bacterial biomembranes as carriers for antitumor therapy. The whole basic fibroblast growth factor (BFGF) molecule (154 amino acids (aa)) was loaded onto bacterial outer membrane vesicles (OMVs) using gene recombination technology. The strong adjuvant effect of OMVs was used to induce the host to produce anti-BFGF autoantibodies. We proved that persistent anti-BFGF autoantibodies can be induced in mice after only 3 immunizations to antagonize BFGF functions. The effects included multiple tumor suppression functions, including inhibition of tumor angiogenesis, induction of tumor cell apoptosis, reversal of tumor immune barriers, and promotion of tumor-specific cytotoxic T lymphocytes (CTLs), eventually causing tumor regression. We confirmed that bacterial biomembranes can be used as a vaccine delivery system to induce the production of antibodies against autoantigens, which may be used for tumor therapy. This study expands the application fields of bacterial biomembrane systems and provides insight for tumor immunotherapy other than monoclonal antibody technology.

PMID: 32251780 [PubMed - as supplied by publisher]

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Gut Microbiota, Its Role in Induction of Alzheimer's Disease Pathology, and Possible Therapeutic Interventions: Special Focus on Anthocyanins.

Cells. 2020 Apr 01;9(4):

Authors: Khan MS, Ikram M, Park JS, Park TJ, Kim MO

Abstract
The human gut is a safe environment for several microbes that are symbiotic and important for the wellbeing of human health. However, studies on gut microbiota in different animals have suggested that changes in the composition and structure of these microbes may promote gut inflammation by releasing inflammatory cytokines and lipopolysaccharides, gut-wall leakage, and may affect systemic inflammatory and immune mechanisms that are important for the normal functioning of the body. There are many factors that aid in the gut's dysbiosis and neuroinflammation, including high stress levels, lack of sleep, fatty and processed foods, and the prolonged use of antibiotics. These neurotoxic mechanisms of dysbiosis may increase susceptibility to Alzheimer's disease (AD) and other neurodegenerative conditions. Therefore, studies have recently been conducted to tackle AD-like conditions by specifically targeting gut microbes that need further elucidation. It was suggested that gut dyshomeostasis may be regulated by using available options, including the use of flavonoids such as anthocyanins, and restriction of the use of high-fatty-acid-containing food. In this review, we summarize the gut microbiota, factors promoting it, and possible therapeutic interventions especially focused on the therapeutic potential of natural dietary polyflavonoid anthocyanins. Our study strongly suggests that gut dysbiosis and systemic inflammation are critically involved in the development of neurodegenerative disorders, and the natural intake of these flavonoids may provide new therapeutic opportunities for preclinical or clinical studies.

PMID: 32244729 [PubMed - as supplied by publisher]

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Antibody-Drug Conjugate Using Ionized Cys-Linker-MMAE as the Potent Payload Shows Optimal Therapeutic Safety.

Cancers (Basel). 2020 Mar 21;12(3):

Authors: Wang Y, Liu L, Fan S, Xiao D, Xie F, Li W, Zhong W, Zhou X

Abstract
Monomethyl auristatin E (MMAE) is the most popular and widely used cytotoxin in the development of antibody-drug conjugates (ADCs). However, current MMAE-based ADCs are all constructed using cleavable linkers, and this design concept still has insurmountable drawbacks. Their potential instabilities and lipophilic MMAE-induced "bystander effect" inevitably increase the toxicity to normal tissues. Herein, we overturn previous negative views of MMAE-based ADCs with non-cleavable linkers and propose using ionized L-Cysteine (Cys)-linker-MMAE as a novel payload, which can ingeniously enrich and enter tumor cells through receptor-mediated endocytosis of antibodies while its lower permeability helps to avoid further off-target toxicity. We demonstrate that Cys-linker-MMAE maintains high potency similar to free MMAE at the tubulin molecular level and can also be efficiently released in target cells. As a result, the preferred ADC (mil40-15) not only exhibits ideal plasma stability and maintains potent cytotoxicity as MMAE (IC50: 10-11 M), but also shows improved safety with lower bystander toxicity (IC50: 10-9 M), its maximum tolerated dose approaching the level of the naked antibody (160 mg/kg). This study indicated that Cys-linker-MMAE has the potential as a potent payload for ADCs, which is expected to provide novel strategies for the development of MMAE-based ADCs.

PMID: 32245171 [PubMed - as supplied by publisher]

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Rapid in vitro assessment of Clostridioides difficile inhibition by probiotics using dielectrophoresis to quantify cell structure alterations.

ACS Infect Dis. 2020 Apr 02;:

Authors: Moore JH, Honrado C, Stagnaro V, Kolling G, Warren CA, Swami NS

Abstract
Clostridioides difficile (C. difficile) infection (CDI) is the primary cause of nosocomial antibiotic-associated diarrhea, with high recurrence rates following initial antibiotic treatment regimens. Restoration of the host gut microbiome through probiotic therapy is under investigation to reduce recurrence. Current in vitro methods to assess C. difficile de-activation by probiotic micro-organisms are based on C. difficile growth inhibition, but the cumbersome and time-consuming nature of the assay limits the number of assessed permutations. Phenotypic alterations to the C. difficile cellular structure upon interaction with probiotics can potentially enable rapid assessment of the inhibition, without the need for extended culture. Since supernatants from cultures of commensal microbiota reflect the complex metabolite milieu that de-activates C. difficile, we explore coculture of C. difficile with an optimal dose of supernatants from probiotic culture to speed growth inhibition assays and enable correlations with alterations to its prolate ellipsoidal structure. Based on sensitivity of electrical polarizability to C. difficile cell shape and subcellular structure, we show that the inhibitory effect of Lactobacillus spp. supernatants on C. difficile can be determined based on the positive dielectrophoresis level within just 1 hour of culture, using a highly toxigenic strain and a clinical isolate, whereas optical and growth inhibition measurements require far greater culture time. We envision application of this in vitro coculture model, in conjunction with dielectrophoresis, to rapidly screen for potential probiotic combinations for the treatment of recurrent CDI.

PMID: 32239920 [PubMed - as supplied by publisher]

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A Slippery Scaffold: Synthesis and Recycling of the Bacterial Cell Wall Carrier Lipid.

J Mol Biol. 2020 Mar 28;:

Authors: Workman SD, Strynadka NCJ

Abstract
The biosynthesis of bacterial cell envelope polysaccharides such as peptidoglycan relies on the use of a dedicated carrier lipid both for the assembly of precursors at the cytoplasmic face of the plasma membrane and for the translocation of lipid linked oligosaccharides across the plasma membrane into the periplasmic space. This dedicated carrier lipid, undecaprenyl phosphate, results from the dephosphorylation of undecaprenyl pyrophosphate, which is generated de novo in the cytoplasm by undecaprenyl pyrophosphate synthase and released as a by-product when newly synthesized glycans are incorporated into the existing cell envelope. The de novo synthesis of undecaprenyl pyrophosphate has been thoroughly characterized from a structural and mechanistic standpoint; however, its dephosphorylation to the active carrier lipid form, both in the course of de novo synthesis and recycling, has only been begun to be studied in depth in recent years. This review provides an overview of bacterial carrier lipid synthesis and presents the current state of knowledge regarding bacterial carrier lipid recycling.

PMID: 32234311 [PubMed - as supplied by publisher]

Take your vitamins: The alpha isoform of folate receptor (FR‐α) is overexpressed in ovarian and endometrial cancer cells. Existing NIR fluorescent probes targeting FR‐α show high non‐specific tissue adsorption. An NIR fluorescent probe, FolateSiR‐1 was designed and synthesized. This probe exhibits very low background fluorescence and afforded a tumor‐to‐background ratio of up to 83 in FR‐expressing tumor‐bearing mice within 30 min after the injection.

Abstract

Folate receptors (FRs) are membrane proteins involved in folic acid uptake, and the alpha isoform (FR‐α) is overexpressed in ovarian and endometrial cancer cells. For fluorescence imaging of FRs in vivo, the near‐infrared (NIR) region (650–900 nm), in which tissue penetration is high and autofluorescence is low, is optimal, but existing NIR fluorescent probes targeting FR‐α show high non‐specific tissue adsorption, and require prolonged washout to visualize tumors. We have designed and synthesized a new NIR fluorescent probe, FolateSiR‐1, utilizing a Si‐rhodamine fluorophore having a carboxy group at the benzene moiety, coupled to a folate ligand moiety through a negatively charged tripeptide linker. This probe exhibits very low background fluorescence and afforded a tumor‐to‐background ratio (TBR) of up to 83 in FR‐expressing tumor‐bearing mice within 30 min. Thus, FolateSiR‐1 has the potential to contribute to the research in the field of biology and the clinical medicine.

A robust fluorescence‐based assay accurately reports on the sugar‐transfer activity of glycosyltransferases. This assay is amenable to high‐throughput screening and should be applicable to a diverse set of group‐transfer enzymes. This assay is validated by screening of a library of known bioactive molecules to identify a new O‐GlcNAc transferase antagonist.

Abstract

Glycosyltransferases carry out important cellular functions in species ranging from bacteria to humans. Despite their essential roles in biology, simple and robust activity assays that can be easily applied to high‐throughput screening for inhibitors of these enzymes have been challenging to develop. Herein, we report a bead‐based strategy to measure the group‐transfer activity of glycosyltransferases sensitively using simple fluorescence measurements, without the need for coupled enzymes or secondary reactions. We validate the performance and accuracy of the assay using O‐GlcNAc transferase (OGT) as a model system through detailed Michaelis–Menten kinetic analysis of various substrates and inhibitors. Optimization of this assay and application to high‐throughput screening enabled screening for inhibitors of OGT, leading to a novel inhibitory scaffold. We believe this assay will prove valuable not only for the study of OGT, but also more widely as a general approach for the screening of glycosyltransferases and other group‐transfer enzymes.

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Development of pepper vein banding virus chimeric virus-like particles for potential diagnostic and therapeutic applications.

Arch Virol. 2020 Mar 30;:

Authors: Sabharwal P, Sushmitha C, Amritha CK, Natraj U, Murthy MRN, Savithri HS

Abstract
Monoclonal antibodies have attracted wide attention in therapeutics owing to their high efficacy, low toxicity, and specific targeting. However, antibodies cannot cross the cell membrane barrier. Therefore, their therapeutic potential is limited to surface-exposed antigens or secreted proteins. In the present investigation, we have developed a chimeric virus-like particle (VLP) of pepper vein banding virus (PVBV) and explored the possibility of using it as a delivery vehicle for antibodies against intracellular antigens as well as for future applications in immunodiagnostics. The chimeric PVBV particles were generated by genetically engineering the B domain of Staphylococcus aureus protein A (SpA) at the N-terminus of the PVBV coat protein (CP). The chimeric VLPs purified by sucrose density gradient centrifugation had ~440-fold higher affinity towards IgG antibody when compared to SpA. Interestingly, the unassembled chimeric CP with the B-domain at the N-terminus (BCP) purified by Ni-NTA chromatography was a monomer, and it had ~45-fold higher affinity towards antibodies compared to SpA. Additionally, the chimeric particles were able to bind and deliver antibodies against both intracellular (α-tubulin) and surface-exposed antigens (CD 20). However, the BCP monomer failed to enter mammalian cells. Thus, for the first time, we have demonstrated that the assembled VLPs are essential for internalization. These results demonstrate the potential of the use of chimeric PVBV VLPs in diagnostics and, more importantly, as nanocarriers for intracellular delivery of antibodies.

PMID: 32232673 [PubMed - as supplied by publisher]

Mighty macrocycles: an in‐depth look at the binding parameters of teixobactin, a macrocyclic antimicrobial peptide, with its membrane target, lipid II. Teixobactin binds to analogues of both Gram‐positive and Gram‐negative bacterial lipids, allowing its activity scope to be extended to both types of organisms using membrane‐disrupting peptides.

Abstract

The prevalence of life‐threatening, drug‐resistant microbial infections has challenged researchers to consider alternatives to currently available antibiotics. Teixobactin is a recently discovered “resistance‐proof” antimicrobial peptide that targets the bacterial cell wall precursor lipid II. In doing so, teixobactin exhibits potent antimicrobial activity against a wide range of Gram‐positive organisms. Herein we demonstrate that teixobactin and several structural analogues are capable of binding lipid II from both Gram‐positive and Gram‐negative bacteria. Furthermore, we show that when combined with known outer membrane‐disrupting peptides, teixobactin is active against Gram‐negative organisms.

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Aryl-alkyl-lysines: Novel agents for treatment of C. difficile infection.

Sci Rep. 2020 Mar 27;10(1):5624

Authors: Ghosh C, AbdelKhalek A, Mohammad H, Seleem MN, Haldar J

Abstract
Clostridium difficile infections (CDIs) are a growing health concern worldwide. The recalcitrance of C. difficile spores to currently available treatments and concomitant virulence of vegetative cells has made it imperative to develop newer modalities of treatment. Aryl-alkyl-lysines have been earlier reported to possess antimicrobial activity against pathogenic bacteria, fungi, and parasites. Their broad spectrum of activity is attributed to their ability to infiltrate microbial membranes. Herein, we report the activity of aryl-alkyl-lysines against C. difficile and associated pathogens. The most active compound NCK-10 displayed activity comparable to the clinically-used antibiotic vancomycin. Indeed, against certain C. difficile strains, NCK-10 was more active than vancomycin in vitro. Additionally, NCK-10 exhibited limited permeation across the intestinal tract as assessed via a Caco-2 bidirectional permeability assay. Overall, the findings suggest aryl-alkyl-lysines warrant further investigation as novel agents to treat CDI.

PMID: 32221399 [PubMed - as supplied by publisher]

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Activity of Cinnamaldehyde on Quorum Sensing and Biofilm Susceptibility to Antibiotics in Pseudomonas aeruginosa.

Microorganisms. 2020 Mar 23;8(3):

Authors: Topa SH, Palombo EA, Kingshott P, Blackall LL

Abstract
Quorum sensing (QS) plays an important role during infection for the opportunistic human pathogen Pseudomonas aeruginosa. Quorum sensing inhibition (QSI) can disrupt this initial event of infection without killing bacterial cells, and thus QS inhibitors have been suggested as novel approaches for anti-infective therapy. Cinnamaldehyde (CAD) is a P. aeruginosa biofilm inhibitor and disperser of preformed biofilms. In this study, the combined use of CAD and colistin (COL) revealed a synergistic activity, but this was not the case for CAD combined with carbenicillin, tobramycin (TOB), or erythromycin in checkerboard assays for P. aeruginosa. CAD demonstrated QSI activity by repression of the expression of lasB, rhlA and pqsA in GFP reporter assays. Approximately 70% reduction in GFP production was observed with the highest CAD concentration tested in all the QS reporter strains. TOB also showed strong QSI when combined with CAD in reporter assays. Combination treatments revealed an additive activity of CAD with COL and TOB in biofilm inhibition (75.2% and 83.9%, respectively) and preformed biofilm dispersion (~90% for both) when compared to the individual treatments. Therefore, a proposed method to mitigate P. aeruginosa infection is a combination therapy of CAD with COL or CAD with TOB as alternatives to current individual drug therapies.

PMID: 32210139 [PubMed]

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Fluorescent Probes for Monitoring Serine Ubiquitination.

Biochemistry. 2020 Mar 24;:

Authors: Puvar K, Saleh AM, Curtis R, Zhou Y, Nyalapatla PR, Fu J, Rovira AR, Tor Y, Luo ZQ, Ghosh AK, Wirth MJ, Chmielewski J, Kinzer-Ursem TL, Das C

Abstract
In a radical departure from the classical E1-E2-E3 three-enzyme mediated ubiquitination of eukaryotes, the recently-described bacterial enzymes of the SidE family of Legionella pneumophila effectors utilize NAD+ to ligate ubiquitin onto target substrate proteins. This outcome is achieved via a two-step mechanism involving (1) ADP-ribosylation of ubiquitin followed by (2) phosphotransfer to a target serine residue. Here, using fluorescent NAD+ analogues as well as synthetic substrate mimics, we have developed continuous assays ena-bling real-time monitoring of both steps of this mechanism. These assays are amenable to biochemical studies and high-throughput screening of inhibitors of these effectors, and the discovery and characterization of putative enzymes similar to the SidE family in other organisms. We also show their utility in studying enzymes that can reverse and inhibit this post-translational modification.

PMID: 32207972 [PubMed - as supplied by publisher]

Combating MRSA : The kalimantacin antibiotics mimic the conformation of the natural fatty acyl substrate to inhibit the activity of the essential enoyl‐ACP reductase enzyme FabI in Staphylococcus aureus . The findings of this study provide insights into the mode of action of this novel class of FabI inhibitors.

Abstract

The enoyl‐acyl carrier protein reductase enzyme FabI is essential for fatty acid biosynthesis in Staphylococcus aureus and represents a promising target for the development of novel, urgently needed anti‐staphylococcal agents. Here, we elucidate the mode of action of the kalimantacin antibiotics, a novel class of FabI inhibitors with clinically‐relevant activity against multidrug‐resistant S. aureus . By combining X‐ray crystallography with molecular dynamics simulations, in vitro kinetic studies and chemical derivatization experiments, we characterize the interaction between the antibiotics and their target, and we demonstrate that the kalimantacins bind in a unique conformation that differs significantly from the binding mode of other known FabI inhibitors. We also investigate mechanisms of acquired resistance in S. aureus and identify key residues in FabI that stabilize the binding of the antibiotics. Our findings provide intriguing insights into the mode of action of a novel class of FabI inhibitors that will inspire future anti‐staphylococcal drug development.

Nature, Published online: 24 March 2020; doi:10.1038/d41586-020-00895-8

New York City researchers hope antibody-rich plasma can keep people out of intensive care.

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RNA Splicing: A New Paradigm in Host-Pathogen Interactions.

J Mol Biol. 2019 04 05;431(8):1565-1575

Authors: Chauhan K, Kalam H, Dutt R, Kumar D

Abstract
RNA splicing brings diversity to the eukaryotic proteome. Different spliced variants of a gene may differ in their structure, function, localization, and stability influencing protein stoichiometry and physiological outcomes. Alternate spliced variants of different genes are known to associate with various chronic pathologies including cancer. Emerging evidence suggests precise regulation of splicing as fundamental to normal well-being. In this context, infection-induced alternative splicing has emerged as a new pivot of host function, which pathogenic microbes can alter-directly or indirectly-to tweak the host immune responses against the pathogen. The implications of these findings are vast, and although not explored much in the case of pathogenic infections, we present here examples from splicing mediated regulation of immune responses across a variety of conditions and explore how this fascinating finding brings a new paradigm to host-pathogen interactions.

PMID: 30857970 [PubMed - indexed for MEDLINE]

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Anticancer effect of bacteria on cervical cancer: Molecular aspects and therapeutic implications.

Life Sci. 2020 Apr 01;246:117413

Authors: Pourmollaei S, Barzegari A, Farshbaf-Khalili A, Nouri M, Fattahi A, Shahnazi M, Dittrich R

Abstract
Cervical cancer is the second common cancer and the third leading cause of cancer deaths among women in less developed countries. It has been indicated that changes in vaginal microbiome play an important role in the occurrence and development of cervical cancer. However, studies have shown that probiotics play an effective role in fighting cancer by affecting pathogenic bacteria, inducing cancer cells apoptosis, and other anticancer activities. Therefore, the purpose of the present study is reviewing the anticancer effect of cervicovaginal bacteria and their potential for cervical cancer treatment.

PMID: 32035929 [PubMed - indexed for MEDLINE]

Nature Biotechnology, Published online: 23 March 2020; doi:10.1038/s41587-020-0462-y

Primary macrophages engineered to express chimeric antigen receptors have anti-tumor activity in humanized mice.

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Structures of Bacterial MraY and Human GPT Provide Insights into Rational Antibiotic Design.

J Mol Biol. 2020 Mar 18;:

Authors: Mashalidis EH, Lee SY

Abstract
The widespread emergence of antibiotic resistance in pathogens necessitates the development of antibacterial agents inhibiting underexplored targets in bacterial metabolism. One such target is MraY (phospho-MurNAc-pentapeptide translocase), an essential integral membrane enzyme that catalyzes the first committed step of peptidoglycan biosynthesis. MraY has long been considered a promising candidate for antibiotic development in part because it is the target of five classes of naturally occurring nucleoside inhibitors with potent in vivo and in vitro antibacterial activity. Although these inhibitors each have a nucleoside moiety, they vary dramatically in their core structures, and they have different activity properties. Until recently, the structural basis of MraY inhibition was poorly understood. Several recent structures of MraY and its human paralog, GPT (GlcNAc-1-P-transferase), have provided insights into MraY inhibition that are consistent with known inhibitor activity data and can inform rational drug design for this important antibiotic target.

PMID: 32199982 [PubMed - as supplied by publisher]