Browsing by Subject "GRAM-NEGATIVE BACTERIA"

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  • Sartelli, Massimo; Weber, Dieter G.; Ruppe, Etienne; Bassetti, Matteo; Wright, Brian J.; Ansaloni, Luca; Catena, Fausto; Coccolini, Federico; Abu-Zidan, Fikri M.; Coimbra, Raul; Moore, Ernest E.; Moore, Frederick A.; Maier, Ronald V.; De Waele, Jan J.; Kirkpatrick, Andrew W.; Griffiths, Ewen A.; Eckmann, Christian; Brink, Adrian J.; Mazuski, John E.; May, Addison K.; Sawyer, Rob G.; Mertz, Dominik; Montravers, Philippe; Kumar, Anand; Roberts, Jason A.; Vincent, Jean-Louis; Watkins, Richard R.; Lowman, Warren; Spellberg, Brad; Abbott, Iain J.; Adesunkanmi, Abdulrashid Kayode; Al-Dahir, Sara; Al-Hasan, Majdi N.; Agresta, Ferdinando; Althani, Asma A.; Ansari, Shamshul; Ansumana, Rashid; Augustin, Goran; Bala, Miklosh; Balogh, Zsolt J.; Baraket, Oussama; Bhangu, Aneel; Beltran, Marcelo A.; Bernhard, Michael; Biffl, Walter L.; Boermeester, Marja A.; Brecher, Stephen M.; Cherry-Bukowiec, Jill R.; Buyne, Otmar R.; Cainzos, Miguel A.; Cairns, Kelly A.; Camacho-Ortiz, Adrian; Chandy, Sujith J.; Jusoh, Asri Che; Chichom-Mefire, Alain; Colijn, Caroline; Corcione, Francesco; Cui, Yunfeng; Curcio, Daniel; Delibegovic, Samir; Demetrashvili, Zaza; De Simone, Belinda; Dhingra, Sameer; Diaz, Jose J.; Di Carlo, Isidoro; Dillip, Angel; Di Saverio, Salomone; Doyle, Michael P.; Dorj, Gereltuya; Dogjani, Agron; Dupont, Herve; Eachempati, Soumitra R.; Enani, Mushira Abdulaziz; Egiev, Valery N.; Elmangory, Mutasim M.; Ferrada, Paula; Fitchett, Joseph R.; Fraga, Gustavo P.; Guessennd, Nathalie; Giamarellou, Helen; Ghnnam, Wagih; Gkiokas, George; Goldberg, Staphanie R.; Gomes, Carlos Augusto; Gomi, Harumi; Guzman-Blanco, Manuel; Haque, Mainul; Hansen, Sonja; Hecker, Andreas; Heizmann, Wolfgang R.; Herzog, Torsten; Hodonou, Adrien Montcho; Hong, Suk-Kyung; Kafka-Ritsch, Reinhold; Kaplan, Lewis J.; Kapoor, Garima; Karamarkovic, Aleksandar; Kees, Martin G.; Kenig, Jakub; Kiguba, Ronald; Kim, Peter K.; Kluger, Yoram; Khokha, Vladimir; Koike, Kaoru; Kok, Kenneth Y. Y.; Kong, Victory; Knox, Matthew C.; Inaba, Kenji; Isik, Arda; Iskandar, Katia; Ivatury, Rao R.; Labbate, Maurizio; Labricciosa, Francesco M.; Laterre, Pierre-Francois; Latifi, Rifat; Lee, Jae Gil; Lee, Young Ran; Leone, Marc; Leppäniemi, Ari; Li, Yousheng; Liang, Stephen Y.; Loho, Tonny; Maegele, Marc; Malama, Sydney; Marei, Hany E.; Martin-Loeches, Ignacio; Marwah, Sanjay; Massele, Amos; McFarlane, Michael; Melo, Renato Bessa; Negoi, Ionut; Nicolau, David P.; Nord, Carl Erik; Ofori-Asenso, Richard; Omari, AbdelKarim H.; Ordonez, Carlos A.; Ouadii, Mouaqit; Pereira Junior, Gerson Alves; Piazza, Diego; Pupelis, Guntars; Rawson, Timothy Miles; Rems, Miran; Rizoli, Sandro; Rocha, Claudio; Sakakhushev, Boris; Sanchez-Garcia, Miguel; Sato, Norio; Lohse, Helmut A. Segovia; Sganga, Gabriele; Siribumrungwong, Boonying; Shelat, Vishal G.; Soreide, Kjetil; Soto, Rodolfo; Talving, Peep; Tilsed, Jonathan V.; Timsit, Jean-Francois; Trueba, Gabriel; Trung, Ngo Tat; Ulrych, Jan; van Goor, Harry; Vereczkei, Andras; Vohra, Ravinder S.; Wani, Imtiaz; Uhl, Waldemar; Xiao, Yonghong; Yuan, Kuo-Ching; Zachariah, Sanoop K.; Zahar, Jean-Ralph; Zakrison, Tanya L.; Corcione, Antonio; Melotti, Rita M.; Viscoli, Claudio; Viale, Perluigi (2016)
    Intra-abdominal infections (IAI) are an important cause of morbidity and are frequently associated with poor prognosis, particularly in high-risk patients. The cornerstones in the management of complicated IAIs are timely effective source control with appropriate antimicrobial therapy. Empiric antimicrobial therapy is important in the management of intra-abdominal infections and must be broad enough to cover all likely organisms because inappropriate initial antimicrobial therapy is associated with poor patient outcomes and the development of bacterial resistance. The overuse of antimicrobials is widely accepted as a major driver of some emerging infections (such as C. difficile), the selection of resistant pathogens in individual patients, and for the continued development of antimicrobial resistance globally. The growing emergence of multi-drug resistant organisms and the limited development of new agents available to counteract them have caused an impending crisis with alarming implications, especially with regards to Gram-negative bacteria. An international task force from 79 different countries has joined this project by sharing a document on the rational use of antimicrobials for patients with IAIs. The project has been termed AGORA (Antimicrobials: A Global Alliance for Optimizing their Rational Use in Intra-Abdominal Infections). The authors hope that AGORA, involving many of the world's leading experts, can actively raise awareness in health workers and can improve prescribing behavior in treating IAIs.
  • Ottman, Noora; Huuskonen, Laura; Reunanen, Justus; Boeren, Sjef; Klievink, Judith; Smidt, Hauke; Belzer, Clara; de Vos, Willem M. (2016)
    Akkermansia muciniphila is a common member of the human gut microbiota and belongs to the Planctomycetes-Verrucomicrobia-Chlamydiae superphylum. Decreased levels of A. muciniphila have been associated with many diseases, and thus it is considered to be a beneficial resident of the intestinal mucus layer. Surface-exposed molecules produced by this organism likely play important roles in colonization and communication with other microbes and the host, but the protein composition of the outer membrane (OM) has not been characterized thus far. Herein we set out to identify and characterize A. muciniphila proteins using an integrated approach of proteomics and computational analysis. Sarkosyl extraction and sucrose density-gradient centrifugation methods were used to enrich and fractionate the OM proteome of A. muciniphila. Proteins from these fractions were identified by LC-MS/MS and candidates for OM proteins derived from the experimental approach were subjected to computational screening to verify their location in the cell. In total we identified 79 putative OM and membrane-associated extracellular proteins, and 23 of those were found to differ in abundance between cells of A. muciniphila grown on the natural substrate, mucin, and those grown on the non-mucus sugar, glucose. The identified OM proteins included highly abundant proteins involved in secretion and transport, as well as proteins predicted to take part in formation of the pili-like structures observed in A. muciniphila. The most abundant OM protein was a 95-kD protein, termed PilQ, annotated as a type IV pili secretin and predicted to be involved in the production of pili in A. muciniphila. To verify its location we purified the His-Tag labeled N-terminal domain of PilQ and generated rabbit polyclonal antibodies. Immunoelectron microscopy of thin sections immunolabeled with these antibodies demonstrated the OM localization of PilQ, testifying for its predicted function as a type IV pili secretin in A. muciniphila. As pili structures are known to be involved in the modulation of host immune responses, this provides support for the involvement of OM proteins in the host interaction of A. muciniphila. In conclusion, the characterization of A. muciniphila OM proteome provides valuable information that can be used for further functional and immunological studies.
  • Weirich, Johanna; Braeutigam, Cornelia; Muehlenkamp, Melanie; Franz-Wachtel, Mirita; Macek, Boris; Meuskens, Ina; Skurnik, Mikael; Leskinen, Katarzyna; Bohn, Erwin; Autenrieth, Ingo; Schuetz, Monika (2017)
    The emergence of multiresistant Gram-negative bacteria requires new therapies for combating bacterial infections. Targeting the biogenesis of virulence factors could be an alternative strategy instead of killing bacteria with antibiotics. The outer membrane (OM) of Gram-negative bacteria acts as a physical barrier. At the same time it facilitates the exchange of molecules and harbors a multitude of proteins associated with virulence. In order to insert proteins into the OM, an essential oligomeric membrane-associated protein complex, the ss-barrel assembly machinery (BAM) is required. Being essential for the biogenesis of outer membrane proteins (OMPs) the BAM and also periplasmic chaperones may serve as attractive targets to develop novel antiinfective agents. Herein, we aimed to elucidate which proteins belonging to the OMP biogenesis machinery have the most important function in granting bacterial fitness, OM barrier function, facilitating biogenesis of dedicated virulence factors and determination of overall virulence. To this end we used the enteropathogen Yersinia enterocolitica as a model system. We individually knocked out all non-essential components of the BAM (BamB, C and E) as well as the periplasmic chaperones DegP, SurA and Skp. In summary, we found that the most profound phenotypes were produced by the loss of BamB or SurA with both knockouts resulting in significant attenuation or even avirulence of Ye in a mouse infection model. Thus, we assume that both BamB and SurA are promising targets for the development of new antiinfective drugs in the future.
  • Bauwens, Eva; Joosten, Myrthe; Taganna, Joemar; Rossi, Mirko; Debraekeleer, Ayla; Tay, Alfred; Peters, Fanny; Backert, Steffen; Fox, James; Ducatelle, Richard; Remaut, Han; Haesebrouck, Freddy; Smet, Annemieke (2018)
    Helicobacter (H.) pylori is an important risk factor for gastric malignancies worldwide. Its outer membrane proteome takes an important role in colonization of the human gastric mucosa. However, in zoonotic non-H. pylori helicobacters (NHPHs) also associated with human gastric disease, the composition of the outer membrane (OM) proteome and its relative contribution to disease remain largely unknown. By means of a comprehensive survey of the diversity and distribution of predicted outer membrane proteins (OMPs) identified in all known gastric Helicobacter species with fully annotated genome sequences, we found genus- and species-specific families known or thought to be implicated in virulence. Hop adhesins, part of the Helicobacter-specific family 13 (Hop, Hor and Horn) were restricted to the gastric species H. pylori, H. cetorum and H. acinonychis. Hof proteins (family 33) were putative adhesins with predicted Occ- or MOMP-family like 18-stranded beta-barrels. They were found to be widespread amongst all gastric Helicobacter species only sporadically detected in enterohepatic Helicobacter species. These latter are other members within the genus Helicobacter, although ecologically and genetically distinct. LpxR, a lipopolysaccharide remodeling factor, was also detected in all gastric Helicobacter species but lacking as well from the enterohepatic species H. cinaedi, H. equorum and H. hepaticus. In conclusion, our systemic survey of Helicobacter OMPs points to species and infection-site specific members that are interesting candidates for future virulence and colonization studies.
  • Bozcal, Elif; Dagdeviren, Melih; Uzel, Atac; Skurnik, Mikael (2017)
    It is crucial to understand the in vitro and in vivo regulation of the virulence factor genes of bacterial pathogens. In this study, we describe the construction of a versatile reporter system for Yersinia enterocolitica serotype O:3 (YeO3) based on the luxCDABE operon. In strain YeO3-luxCDE we integrated the luciferase substrate biosynthetic genes, luxCDE, into the genome of the bacterium so that the substrate is constitutively produced. The luxAB genes that encode the luciferase enzyme were cloned into a suicide vector to allow cloning of any promoter-containing fragment upstream the genes. When the obtained suicide-construct is mobilized into YeO3-luxCDE bacteria, it integrates into the recipient genome via homologous recombination between the cloned promoter fragment and the genomic promoter sequence and thereby generates a single-copy and stable promoter reporter. Lipopolysaccharide (LPS) O-antigen (O-ag) and outer core hexasaccharide (OC) of YeO3 are virulence factors necessary to colonization of the intestine and establishment of infection. To monitor the activities of the OC and O-ag gene cluster promoters we constructed the reporter strains YeO3-P-oc::luxAB and YeO3-P-op1::luxAB, respectively. In vitro, at 37 degrees C both promoter activities were highest during logarithmic growth and decreased when the bacteria entered stationary growth phase. At 22 degrees C the OC gene cluster promoter activity increased during the late logarithmic phase. Both promoters were more active in late stationary phase. To monitor the promoter activities in vivo, mice were infected intragastrically and the reporter activities monitored by the IVIS technology. The mouse experiments revealed that both LPS promoters were well expressed in vivo and could be detected by IVIS, mainly from the intestinal region of orally infected mice.
  • Mosselhy, Dina A.; Granbohm, Henrika; Hynonen, Ulla; Ge, Yanling; Palva, Airi; Nordstrom, Katrina; Hannula, Simo-Pekka (2017)
    Infected superficial wounds were traditionally controlled by topical antibiotics until the emergence of antibiotic-resistant bacteria. Silver (Ag) is a kernel for alternative antibacterial agents to fight this resistance quandary. The present study demonstrates a method for immobilizing small-sized (similar to 5 nm) silver nanoparticles on silica matrix to form a nanosilver-silica (Ag-SiO2) composite and shows the prolonged antibacterial effects of the composite in vitro. The composite exhibited a rapid initial Ag release after 24 h and a slower leaching after 48 and 72 h and was effective against both methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli). Ultraviolet (UV)-irradiation was superior to filter-sterilization in retaining the antibacterial effects of the composite, through the higher remaining Ag concentration. A gauze, impregnated with the Ag-SiO2 composite, showed higher antibacterial effects against MRSA and E. coli than a commercial Ag-containing dressing, indicating a potential for the management and infection control of superficial wounds. Transmission and scanning transmission electron microscope analyses of the composite-treated MRSA revealed an interaction of the released silver ions with the bacterial cytoplasmic constituents, causing ultimately the loss of bacterial membranes. The present results indicate that the Ag-SiO2 composite, with prolonged antibacterial effects, is a promising candidate for wound dressing applications.
  • Kiessling, Andreas R.; Malik, Anchal; Goldman, Adrian (2020)
    Adhesion is the initial step in the infection process of gram-negative bacteria. It is usually followed by the formation of biofilms that serve as a hub for further spread of the infection. Type V secretion systems engage in this process by binding to components of the extracellular matrix, which is the first step in the infection process. At the same time they provide protection from the immune system by either binding components of the innate immune system or by establishing a physical layer against aggressors. Trimeric autotransporter adhesins (TAAs) are of particular interest in this family of proteins as they possess a unique structural composition which arises from constraints during translocation. The sequence of individual domains can vary dramatically while the overall structure can be very similar to one another. This patchwork approach allows researchers to draw conclusions of the underlying function of a specific domain in a structure-based approach which underscores the importance of solving structures of yet uncharacterized TAAs and their individual domains to estimate the full extent of functions of the protein a priori. Here, we describe recent advances in understanding the translocation process of TAAs and give an overview of structural motifs that are unique to this class of proteins. The role of BpaC in the infection process of Burkholderia pseudomallei is highlighted as an exceptional example of a TAA being at the centre of infection initiation.
  • Tyrrell, Jonathan M.; Aboklaish, Ali F.; Walsh, Timothy R.; Vaara, Timo; Vaara, Martti (2019)
    The antibiotic crisis has reinstated polymyxins, once abandoned because of their toxicity. Now, preclinical studies have revealed better tolerated and more effective derivatives of polymyxins such as NAB739. Simultaneously, polymyxin-resistant (PMR) strains such as the mcr-1 strains have received lots of justified publicity, even though they are still very rare. Here we show that NAB739 sensitizes the PMR strains to rifampin, a classic "anti-Gram-positive" antibiotic excluded by the intact outer membrane (OM) permeability barrier, as well as to retapamulin, the surrogate of lefamulin, an antibiotic under development against Gram-positive bacteria. Polymyxin B was used as a comparator. The combination of NAB739 and rifampin was synergistic against ten out of eleven PMR strains of Escherichia coll. (Fractional Synergy Indices, FICs, 0.14-0.19) and that of NAB739 and retapamulin against all the tested eleven strains (FICs 0.19-0.25). Against PMR Klebsiella pneumoniae (n = 7), the FICs were 0.13-0.27 for NAB739 + rifampin and 0.14-0.28 for NAB739 + retapamulin. Against Acinetobacter baumannii (n = 2), the combination of NAB739 and rifampin had the FIC of 0.09-0.19. Furthermore, NAB739 and meropenem were synergistic (FICs 0.25-0.50) against four out of five PMR strains that were simultaneously resistant to meropenem.