| 1. |
- Demuth, Andreas, et al.
(författare)
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Pathogenomics: An updated European Research Agenda
- 2008
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Ingår i: Infection, Genetics and Evolution. - : Elsevier BV. - 1567-7257 .- 1567-1348. ; 8:3, s. 386-393
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Tidskriftsartikel (refereegranskat)abstract
- The emerging genomic technologies and bioinformatics provide novel opportunities for studying life-threatening human pathogens and to develop new applications for the improvement of human and animal health and the prevention, treatment, and diagnosis of infections. Based on the ecology and population biology of pathogens and related organisms and their connection to epidemiology, more accurate typing technologies and approaches will lead to better means of disease control. The analysis of the genome plasticity and gene pools of pathogenic bacteria including antigenic diversity and antigenic variation results in more effective vaccines and vaccine implementation programs. The study of newly identified and uncultivated microorganisms enables the identification of new threats. The scrutiny of the metabolism of the pathogen in the host allows the identification of new targets for anti-infectives and therapeutic approaches. The development of modulators of host responses and mediators of host damage will be facilitated by the research on interactions of microbes and hosts, including mechanisms of host damage, acute and chronic relationships as well as commensalisms. The study of multiple pathogenic and non-pathogenic microbes interacting in the host will improve the management of multiple infections and will allow probiotic and prebiotic interventions. Needless to iterate, the application of the results of improved prevention and treatment of infections into clinical tests will have a positive impact on the management of human and animal disease. The Pathogenomics Research Agenda draws on discussions with experts of the Network of Excellence "EuroPathoGenomics" at the management board meeting of the project held during 18-21 April 2007, in the Villa Vigoni, Menaggio, Italy. Based on a proposed European Research Agenda in the field of pathogenomics by the ERA-NET PathoGenoMics the meeting's participants updated the established list of topics as the research agenda for the future.
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| 2. |
- Myint, Si Lhyam, et al.
(författare)
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Ecotin and LamB in Escherichia coli influence the susceptibility to Type VI secretion-mediated interbacterial competition and killing by Vibrio cholerae
- 2021
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Ingår i: Biochimica et Biophysica Acta - General Subjects. - : Elsevier. - 0304-4165 .- 1872-8006. ; 1865:7
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Tidskriftsartikel (refereegranskat)abstract
- Background: A prevailing action of the Type VI secretion system (T6SS) in several Gram-negative bacterial species is inter-bacterial competition. In the past several years, many effectors of T6SS were identified in different bacterial species and their involvement in inter-bacterial interactions were described. However, possible defence mechanisms against T6SS attack among prey bacteria were not well clarified yet. Methods: Escherichia coli was assessed for susceptibility to T6SS-mediated killing by Vibrio cholerae. TheT6SS-mediated bacterial killing assays were performed in absence or presence of different protease inhibitors and with different mutant E. coli strains. Expression levels of selected proteins were monitored using SDS-PAGE and immunoblot analyses. Results: The T6SS-mediated killing of E. coli by V. cholerae was partly blocked when the serine protease inhibitor Pefabloc was present. E. coli lacking the periplasmic protease inhibitor Ecotin showed enhanced susceptibility to killing by V. cholerae. Mutations affecting E. coli membrane stability also caused increased susceptibility to killing by V. cholerae. E. coli lacking the maltodextrin porin protein LamB showed reduced susceptibility to killing by V. cholerae whereas E. coli with induced high levels of LamB showed reduced survival in inter-bacterial competition. Conclusions: Our study identified two proteins in E. coli, the intrinsic protease inhibitor Ecotin and the outer membrane porin LamB, that influenced E. coli susceptibility to T6SS-mediated killing by V. cholerae. General significance: We envision that it is feasible to explore these findings to target and modulate their expression to obtain desired changes in inter-bacterial competition in vivo, e.g. in the gastrointestinal microbiome.
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| 3. |
- Nadeem, Aftab, et al.
(författare)
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A tripartite cytolytic toxin formed by Vibrio cholerae proteins with flagellum-facilitated secretion
- 2021
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 118:47
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Tidskriftsartikel (refereegranskat)abstract
- Vibrio cholerae, responsible for outbreaks of cholera disease, is a highly motile organism by virtue of a single flagellum. We describe how the flagellum facilitates the secretion of three V. cholerae proteins encoded by a hitherto-unrecognized genomic island. The proteins MakA/B/E can form a tripartite toxin that lyses erythrocytes and is cytotoxic to cultured human cells. A structural basis for the cytolytic activity of the Mak proteins was obtained by X-ray crystallography. Flagellum-facilitated secretion ensuring spatially coordinated delivery of Mak proteins revealed a role for the V. cholerae flagellum considered of particular significance for the bacterial environmental persistence. Our findings will pave the way for the development of diagnostics and therapeutic strategies against pathogenic Vibrionaceae.
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| 4. |
- Nadeem, Aftab, et al.
(författare)
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Phosphatidic acid-mediated binding and mammalian cell internalization of the Vibrio cholerae cytotoxin MakA
- 2021
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Ingår i: PLoS Pathogens. - : Public Library of Science. - 1553-7366 .- 1553-7374. ; 17:3
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Tidskriftsartikel (refereegranskat)abstract
- Vibrio cholerae is a noninvasive intestinal pathogen extensively studied as the causative agent of the human disease cholera. Our recent work identified MakA as a potent virulence factor of V. cholerae in both Caenorhabditis elegans and zebrafish, prompting us to investigate the potential contribution of MakA to pathogenesis also in mammalian hosts. In this study, we demonstrate that the MakA protein could induce autophagy and cytotoxicity of target cells. In addition, we observed that phosphatidic acid (PA)-mediated MakA-binding to the host cell plasma membranes promoted macropinocytosis resulting in the formation of an endomembrane-rich aggregate and vacuolation in intoxicated cells that lead to induction of autophagy and dysfunction of intracellular organelles. Moreover, we functionally characterized the molecular basis of the MakA interaction with PA and identified that the N-terminal domain of MakA is required for its binding to PA and thereby for cell toxicity. Furthermore, we observed that the ΔmakA mutant outcompeted the wild-type V. cholerae strain A1552 in the adult mouse infection model. Based on the findings revealing mechanistic insights into the dynamic process of MakA-induced autophagy and cytotoxicity we discuss the potential role played by the MakA protein during late stages of cholera infection as an anti-colonization factor.
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| 5. |
- Nadeem, Aftab, et al.
(författare)
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Protein-lipid interaction at low pH induces oligomerization of the MakA cytotoxin from Vibrio cholerae
- 2022
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Ingår i: eLIFE. - : eLife Sciences Publications, Ltd. - 2050-084X. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- The α-pore-forming toxins (α-PFTs) from pathogenic bacteria damage host cell membranes by pore formation. We demonstrate a remarkable, hitherto unknown mechanism by an α-PFT protein from Vibrio cholerae. As part of the MakA/B/E tripartite toxin, MakA is involved in membrane pore formation similar to other α-PFTs. In contrast, MakA in isolation induces tube-like structures in acidic endosomal compartments of epithelial cells in vitro. The present study unravels the dynamics of tubular growth, which occurs in a pH-, lipid-, and concentration-dependent manner. Within acidified organelle lumens or when incubated with cells in acidic media, MakA forms oligomers and remodels membranes into high-curvature tubes leading to loss of membrane integrity. A 3.7 Å cryo-electron microscopy structure of MakA filaments reveals a unique protein-lipid superstructure. MakA forms a pinecone-like spiral with a central cavity and a thin annular lipid bilayer embedded between the MakA transmembrane helices in its active α-PFT conformation. Our study provides insights into a novel tubulation mechanism of an α-PFT protein and a new mode of action by a secreted bacterial toxin.
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| 6. |
- Toh, Eric, et al.
(författare)
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Bacterial protein MakA causes suppression of tumour cell proliferation via inhibition of PIP5K1α/Akt signalling
- 2022
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Ingår i: Cell Death and Disease. - : Springer Nature. - 2041-4889 .- 2041-4889. ; 13:12
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Tidskriftsartikel (refereegranskat)abstract
- Recently, we demonstrated that a novel bacterial cytotoxin, the protein MakA which is released by Vibrio cholerae, is a virulence factor, causing killing of Caenorhabditis elegans when the worms are grazing on the bacteria. Studies with mammalian cell cultures in vitro indicated that MakA could affect eukaryotic cell signalling pathways involved in lipid biosynthesis. MakA treatment of colon cancer cells in vitro caused inhibition of growth and loss of cell viability. These findings prompted us to investigate possible signalling pathways that could be targets of the MakA-mediated inhibition of tumour cell proliferation. Initial in vivo studies with MakA producing V. cholerae and C. elegans suggested that the MakA protein might target the PIP5K1α phospholipid-signalling pathway in the worms. Intriguingly, MakA was then found to inhibit the PIP5K1α lipid-signalling pathway in cancer cells, resulting in a decrease in PIP5K1α and pAkt expression. Further analyses revealed that MakA inhibited cyclin-dependent kinase 1 (CDK1) and induced p27 expression, resulting in G2/M cell cycle arrest. Moreover, MakA induced downregulation of Ki67 and cyclin D1, which led to inhibition of cell proliferation. This is the first report about a bacterial protein that may target signalling involving the cancer cell lipid modulator PIP5K1α in colon cancer cells, implying an anti-cancer effect.
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| 7. |
- Toh, Eric, et al.
(författare)
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Sublytic activity of a pore-forming protein from commensal bacteria causes epigenetic modulation of tumor-affiliated protein expression
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Cytolysin A (ClyA) is a pore-forming protein expressed at sublytic levels by a strongly silenced gene in non-pathogenic Escherichia coli, including typical commensal isolates in the intestinal microbiome of healthy mammalian hosts. Upon overproduction, the ClyA-expressing bacteria display a cytolytic phenotype. However, it remains unclear whether sublytic amounts of native ClyA play a role in commensal E. coli-host interactions in vivo. Here, we show that sublytic amounts of ClyA are released via outer membrane vesicles (OMVs) and can affect host cells in a profound and remarkable manner. OMVs isolated from ClyA+ E. coli were rapidly internalised into cultured colon cancer cells. The OMV-associated ClyA inhibited the expression of cancer-activating proteins such as H3K27me3, CXCR4, STAT3, and MDM2 via the EZH2/H3K27me3/miR622/CXCR4 signalling axis. Our results demonstrate that sublytic amounts of ClyA in OMVs from non-pathogenic E. coli can target the stability of the EZH2 protein to modulate epigenetics of colon cancer cells
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| 8. |
- Abbara, Aula, et al.
(författare)
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A summary and appraisal of existing evidence of antimicrobial resistance in the Syrian conflict
- 2018
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Ingår i: International Journal of Infectious Diseases. - : Elsevier. - 1201-9712 .- 1878-3511. ; 75, s. 26-33
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Forskningsöversikt (refereegranskat)abstract
- Antimicrobial resistance (AMR) in populations experiencing war has yet to be addressed, despite the abundance of contemporary conflicts and the protracted nature of twenty-first century wars, in combination with growing global concern over conflict-associated bacterial pathogens. The example of the Syrian conflict is used to explore the feasibility of using existing global policies on AMR in conditions of extreme conflict. The available literature on AMR and prescribing behaviour in Syria before and since the onset of the conflict in March 2011 was identified. Overall, there is a paucity of rigorous data before and since the onset of conflict in Syria to contextualize the burden of AMR. However, post onset of the conflict, an increasing number of studies conducted in neighbouring countries and Europe have reported AMR in Syrian refugees. High rates of multidrug resistance, particularly Gram-negative organisms, have been noted amongst Syrian refugees when compared with local populations. Conflict impedes many of the safeguards against AMR, creates new drivers, and exacerbates existing ones. Given the apparently high rates of AMR in Syria, in neighbouring countries hosting refugees, and in European countries providing asylum, this requires the World Health Organization and other global health institutions to address the causes, costs, and future considerations of conflict-related AMR as an issue of global governance. (c) 2018 The Authors. Published by Elsevier Ltd on behalf of International Society for Infectious Diseases.
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| 9. |
- Abbara, Aula, et al.
(författare)
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Antimicrobial resistance in the context of the Syrian conflict : Drivers before and after the onset of conflict and key recommendations
- 2018
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Ingår i: International Journal of Infectious Diseases. - : Elsevier. - 1201-9712 .- 1878-3511. ; 73, s. 1-6
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Forskningsöversikt (refereegranskat)abstract
- Current evidence describing antimicrobial resistance (AMR) in the context of the Syrian conflict is of poor quality and sparse in nature. This paper explores and reports the major drivers of AMR that were present in Syria pre-conflict and those that have emerged since its onset in March 2011. Drivers that existed before the conflict included a lack of enforcement of existing legislation to regulate over-the-counter antibiotics and notification of communicable diseases. This contributed to a number of drivers of AMR after the onset of conflict, and these were also compounded by the exodus of trained staff, the increase in overcrowding and unsanitary conditions, the increase in injuries, and economic sanctions limiting the availability of required laboratory medical materials and equipment. Addressing AMR in this context requires pragmatic, multifaceted action at the local, regional, and international levels to detect and manage potentially high rates of multidrug-resistant infections. Priorities are (1) the development of a competent surveillance system for hospital-acquired infections, (2) antimicrobial stewardship, and (3) the creation of cost-effective and implementable infection control policies. However, it is only by addressing the conflict and immediate cessation of the targeting of health facilities that the rehabilitation of the health system, which is key to addressing AMR in this context, can progress.
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| 10. |
- Ahmad, Irfan, et al.
(författare)
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A Cyclic-di-GMP signalling network regulates biofilm formation and surface associated motility of Acinetobacter baumannii 17978
- 2020
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Acinetobacter baumannii has emerged as an increasing multidrug-resistant threat in hospitals and a common opportunistic nosocomial pathogen worldwide. However, molecular details of the pathogenesis and physiology of this bacterium largely remain to be elucidated. Here we identify and characterize the c-di-GMP signalling network and assess its role in biofilm formation and surface associated motility. Bioinformatic analysis revealed eleven candidate genes for c-di-GMP metabolizing proteins (GGDEF/EAL domain proteins) in the genome of A. baumannii strain 17978. Enzymatic activity of the encoded proteins was assessed by molecular cloning and expression in the model organisms Salmonella typhimurium and Vibrio cholerae. Ten of the eleven GGDEF/EAL proteins altered the rdar morphotype of S. typhimurium and the rugose morphotype of V. cholerae. The over expression of three GGDEF proteins exerted a pronounced effect on colony formation of A. baumannii on Congo Red agar plates. Distinct panels of GGDEF/EAL proteins were found to alter biofilm formation and surface associated motility of A. baumannii upon over expression. The GGDEF protein A1S_3296 appeared as a major diguanylate cyclase regulating macro-colony formation, biofilm formation and the surface associated motility. AIS_3296 promotes Csu pili mediated biofilm formation. We conclude that a functional c-di-GMP signalling network in A. baumannii regulates biofilm formation and surface associated motility of this increasingly important opportunistic bacterial pathogen.
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