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gram negative bacteria

Sandrine Alibert, Joannah N'Gompazza Diarra, Jessica Hernandez, Aurélien Stutzmann, Marwa Fouad, Gérard Boyer, Jean-Marie Pagès
Worrying levels of bacterial resistance have been reported worldwide involving the failure of many available antibiotic treatments. Multidrug resistance (MDR) in Gram-negative bacteria is often ascribed to the presence of multiple and different resistance mechanisms in the same strain. RND efflux pumps play a major role and are an attractive target to discover new antibacterial drugs. Areas covered: This review discusses the prevalence of efflux pumps, their overexpression in clinical scenarios, their polyselectivity, their effect on the intracellular concentrations of various antibiotics associated with the alteration of the membrane permeability and their involvement in pathogenicity are discussed...
October 20, 2016: Expert Opinion on Drug Metabolism & Toxicology
Li Fang, Qiong Chen, Keren Shi, Xi Li, Qiucheng Shi, Fang He, Jiancang Zhou, Yunsong Yu, Xiaoting Hua
Klebsiella pneumoniae is a gram-negative bacterium that causes numerous diseases, including pneumonia and urinary tract infections. An increase in multidrug resistance has complicated the treatment of these bacterial infections, and although tigecycline shows activity against a broad spectrum of bacteria, resistant strains have emerged. In this study, the whole genomes of two clinical and six laboratory-evolved strains were sequenced to identify putative mutations related to tigecycline resistance. Of seven tigecycline-resistant strains, seven (100%) had ramR mutations, five (71...
2016: PloS One
Julia I Tandberg, Leidy X Lagos, Petter Langlete, Eva Berger, Anne-Lise Rishovd, Norbert Roos, Deepa Varkey, Ian T Paulsen, Hanne C Winther-Larsen
Membrane vesicles (MVs) are spherical particles naturally released from the membrane of Gram-negative bacteria. Bacterial MV production is associated with a range of phenotypes including biofilm formation, horizontal gene transfer, toxin delivery, modulation of host immune responses and virulence. This study reports comparative profiling of MVs from bacterial strains isolated from three widely disperse geographical areas. Mass spectrometry identified 119, 159 and 142 proteins in MVs from three different strains of Piscirickettsia salmonis isolated from salmonids in Chile (LF-89), Norway (NVI 5692) and Canada (NVI 5892), respectively...
2016: PloS One
Fatima Belkhadem, Adil A Othman
Four N- and S-glycosides 13-16 having nucleobases 7-12 binding to sugar molecules from one side and to 3,5-dinitrophenyl moieties from another side were synthesized from 3,5-dinitrobenzoic acid 2. The synthetic intermediates, hydrazide 5 and thiosemicarbazide 6 regarded as important key compounds for the synthesis of nucleobases 7-12, each was obtained by two approaches. Structures of synthesized compounds were determined spectroscopically. Antibacterial activities for synthetic intermediates and glycosides were assessed using the paper disk diffusion method against Gram-negative bacteria: Pseudomonas aeruginosa, Pseudomonas fluorescens, and Escherichia coli and Gram-positive bacteria: Bacillus cereus and Staphylococcus aureus...
October 19, 2016: Molecular Diversity
Paola Sperandeo, Alessandra M Martorana, Alessandra Polissi
The outer membrane (OM) of Gram-negative bacteria is an asymmetric lipid bilayer containing a unique glycolipid, lipopolysaccharide (LPS) in its outer leaflet. LPS molecules confer to the OM peculiar permeability barrier properties enabling Gram-negative bacteria to exclude many toxic compounds, including clinically useful antibiotics, and to survive harsh environments. Transport of LPS poses several problems to the cells due to the amphipatic nature of this molecule. In this review we summarize the current knowledge on the LPS transport machinery, discuss the challenges associated with this process and present the solutions that bacterial cells have evolved to address the problem of LPS transport and assembly at the cell surface...
October 17, 2016: Biochimica et Biophysica Acta
Teresa A Garrett
Mass spectrometry of lipids, especially those isolated from bacteria, has ballooned over the past two decades, affirming in the process the complexity of the lipidome. With this has come the identification of new and interesting lipid structures. Here is an overview of several novel lipids, from both Gram-negative and Gram-positive bacteria with roles in health and disease, whose structural identification was facilitated using mass spectrometry. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E...
October 17, 2016: Biochimica et Biophysica Acta
Seonghoon Kim, Dhilon S Patel, Soohyung Park, Joanna Slusky, Jeffery B Klauda, Göran Widmalm, Wonpil Im
Lipid A is the lipid anchor of a lipopolysaccharide in the outer leaflet of the outer membrane of Gram-negative bacteria. In general, lipid A consists of two phosphorylated N-acetyl glucosamine and several acyl chains that are directly linked to the two sugars. Depending on the bacterial species and environments, the acyl chain number and length vary, and lipid A can be chemically modified with phosphoethanolamine, aminoarabinose, or glycine residues, which are key to bacterial pathogenesis. In this work, homogeneous lipid bilayers of 21 distinct lipid A types from 12 bacterial species are modeled and simulated to investigate the differences and similarities of their membrane properties...
October 18, 2016: Biophysical Journal
Maite L Ortiz-Suarez, Firdaus Samsudin, Thomas J Piggot, Peter J Bond, Syma Khalid
OmpA is a multidomain protein found in the outer membranes of most Gram-negative bacteria. Despite a wealth of reported structural and biophysical studies, the structure-function relationships of this protein remain unclear. For example, it is still debated whether it functions as a pore, and the precise molecular role it plays in attachment to the peptidoglycan of the periplasm is unknown. The absence of a consensus view is partly due to the lack of a complete structure of the full-length protein. To address this issue, we performed molecular-dynamics simulations of the full-length model of the OmpA dimer proposed by Robinson and co-workers...
October 18, 2016: Biophysical Journal
Marissa B Guzzo, Hoa T Nguyen, Thanh H Pham, Monika Wyszczelska-Rokiel, Hieronim Jakubowski, Kerstin A Wolff, Sam Ogwang, Joseph L Timpona, Soumya Gogula, Michael R Jacobs, Markus Ruetz, Bernhard Kräutler, Donald W Jacobsen, Guo-Fang Zhang, Liem Nguyen
The methylfolate trap, a metabolic blockage associated with anemia, neural tube defects, Alzheimer's dementia, cardiovascular diseases, and cancer, was discovered in the 1960s, linking the metabolism of folate, vitamin B12, methionine and homocysteine. However, the existence or physiological significance of this phenomenon has been unknown in bacteria, which synthesize folate de novo. Here we identify the methylfolate trap as a novel determinant of the bacterial intrinsic death by sulfonamides, antibiotics that block de novo folate synthesis...
October 2016: PLoS Pathogens
Jlenia Brunetti, Giulia Roscia, Ilaria Lampronti, Roberto Gambari, Leila Quercini, Chiara Falciani, Luisa Bracci, Alessandro Pini
The synthetic antimicrobial peptide SET-M33 has strong activity against bacterial infections due to Gram-negative bacteria. It is currently in preclinical development as a new drug to treat lung infections caused by Gram-negative bacteria. Here we report its strong anti-inflammatory activity in terms of reduced expression of a number of cytokines, enzymes and signal transduction factors involved in inflammation triggered by lipopolysaccharides (LPS) from P. aeruginosa, K. pneumoniae and E. coli. Sixteen cytokines and other major agents involved in inflammation were analyzed in macrophages and bronchial cells after stimulation with LPS and incubation with SET-M33...
October 7, 2016: Journal of Biological Chemistry
Peng Sang, Yan Shi, Peng Teng, Annie Cao, Hai Xu, Qi Li, Jianfeng Cai
Antibiotic resistance is one of the biggest public concerns in the 21st century. Host-defense peptides (HDPs) can potentially mitigate the problem through the disruption of bacterial membranes; however, they suffer from moderate activity and low stability. We recently developed a new class of peptidomimetics termed "AApeptides". This class of peptidomimetics can mimic the mechanism of action of HDPs, and effectively arrest the growth of multidrug resistant Gram-positive and Gram-negative bacteria. As they are built on unnatural backbone, they are highly resistant to proteolytic degradation...
October 18, 2016: Current Topics in Medicinal Chemistry
Grzegorz Majka, Grażyna Więcek, Małgorzata Śróttek, Klaudyna Śpiewak, Małgorzata Brindell, Joanna Koziel, Janusz Marcinkiewicz, Magdalena Strus
Translocation of bacteria, primarily Gram-negative pathogenic flora, from the intestinal lumen into the circulatory system leads to sepsis. In newborns, and especially very low birth weight infants, sepsis is a major cause of morbidity and mortality. The results of recently conducted clinical trials suggest that lactoferrin, an iron-binding protein that is abundant in mammalian colostrum and milk, may be an effective agent in preventing sepsis in newborns. However, despite numerous basic studies on lactoferrin, very little is known about how metal saturation of this protein affects a host's health...
October 18, 2016: Biometals: An International Journal on the Role of Metal Ions in Biology, Biochemistry, and Medicine
Ia Kusradze, Natia Karumidze, Sophio Rigvava, Teona Dvalidze, Malkhaz Katsitadze, Irakli Amiranashvili, Marina Goderdzishvili
Acinetobacter baumannii is a gram-negative, non-motile bacterium that, due to its multidrug resistance, has become a major nosocomial pathogen. The increasing number of multidrug resistant (MDR) strains has renewed interest in phage therapy. The aim of our study was to assess the effectiveness of phage administration in Acinetobacter baumannii wound infections in an animal model to demonstrate phage therapy as non-toxic, safe and alternative antibacterial remedy. Using classical methods for the study of bacteriophage properties, we characterized phage vB-GEC_Ab-M-G7 as a dsDNA myovirus with a 90 kb genome size...
2016: Frontiers in Microbiology
Yuji Watanabe, Nozomi Oikawa, Maya Hariu, Ryota Fuke, Masafumi Seki
Procalcitonin (PCT) and C-reactive protein serve as biomarkers of infection in patients with sepsis/bacteremia. The present study assessed the clinical characteristics of 280 patients with suspected sepsis who were admitted to Tohoku Medical and Pharmaceutical University Hospital between January 2012 and December 2013. Among the patients, 133 and 147 were positive and negative for PCT, respectively. Patients who were PCT positive were older and more frequently male, had reduced levels of platelets and albumin, and increased levels of aspartate aminotransferase, alanine aminotransferase, blood urea nitrogen, creatinine, and C-reactive protein...
2016: International Journal of General Medicine
Ai-Jun Pan, Qing Mei, Ying Ye, Hong-Ru Li, Bao Liu, Jia-Bin Li
The purpose of this study was to validate the mutant selection window (MSW) hypothesis in vitro and in vivo with Escherichia coli and Pseudomonas aeruginosa exposed to fosfomycin. Two standard strains of Gram-negative bacteria, those are E. coli ATCC 25922 and P. aeruginosa ATCC 27853, were exposed to fosfomycin at concentrations below MIC, between the MIC and the mutant prevention concentration (MPC), and above the MPC in Luria-Bertani broth and in a tissue-cage infection model, respectively. With the in vitro time-kill studies, there were bacterial re-growth and emergence of resistance thereafter for both strains at antibiotic concentrations of × 4, × 8 and × 16 MIC...
October 19, 2016: Journal of Antibiotics
Darja Kušar, Karin Šrimpf, Petra Isaković, Lina Kalšek, Javid Hosseini, Irena Zdovc, Tina Kotnik, Modest Vengušt, Gabrijela Tavčar-Kalcher
BACKGROUND: Bacterial intercellular communication, called quorum sensing, takes place via the production and collective response to signal molecules. In Gram-negative bacteria, like Pseudomonas aeruginosa, these signaling molecules are N-acylhomoserine lactones (AHLs). P. aeruginosa is a common cause of inflammation of the ear canal (otitis externa) in dogs. It employs quorum sensing to coordinate the expression of host tissue-damaging factors, which are largely responsible for its virulence...
October 18, 2016: BMC Veterinary Research
Dar-Chone Chow, Kacie Rice, Wanzhi Huang, Robert L Atmar, Timothy G Palzkill
The β-lactamase inhibitory protein (BLIP) binds and inhibits a wide range of class A β-lactamases including the TEM-1 β-lactamase (Ki= 0.5 nM), which is widely present in Gram-negative bacteria, and the KPC-2 β-lactamase (Ki= 1.2 nM), which hydrolyzes virtually all clinically useful β-lactam antibiotics. The extent to which the specificity of a protein that binds a broad range of targets can be modified to display narrow specificity was explored in this study by engineering BLIP to bind selectively to KPC-2 β-lactamase...
October 18, 2016: ACS Infectious Diseases
Zhijie Pan, Rong Liu, Pei Zhang, Hua Zhou, Yiqi Fu, Jianying Zhou
Raoultella planticola is a gram-negative bacterium that rarely causes diseases in humans. Here, we present a case of hospital-acquired pneumonia caused by R. planticola that likely originated in the gastrointestinal tract. To the best of our knowledge, this is the second report describing the detection of the gene New Delhi Metallo-β-lactamase-1 (blaNDM-1) in multidrug-resistant R. planticola. Clinical samples were collected for bacterial culture and antimicrobial susceptibility testing from a patient during hospitalization...
October 18, 2016: Microbial Drug Resistance: MDR: Mechanisms, Epidemiology, and Disease
Taeho Kim, Gary B Braun, Zhi-Gang She, Sazid Hussain, Erkki Ruoslahti, Michael J Sailor
A theranostic nanoparticle with biochemically triggered antibacterial activity is demonstrated. Metallic silver is deposited onto porous silicon nanoparticles (pSiNPs) by galvanic displacement. When aqueous diaminesilver ([Ag(NH3)2](+)) is used as a silver source, the pSiNPs template the crystalline silver as small (mean diameter 13 nm) and well-dispersed nanoparticles embedded within and on the larger (100 nm) pSiNPs. The silver nanoparticles quench intrinsic photoluminescence (PL) from the porous silicon matrix...
October 18, 2016: ACS Applied Materials & Interfaces
Wen-Shuo Kuo, Chia-Yuan Chang, Hua-Han Chen, Chih-Li Lilian Hsu, Jiu-Yao Wang, Hui-Fang Kao, Lawrence Chao-Shan Chou, Yi-Chun Chen, Shean-Jen Chen, Wen-Tsan Chang, Shih-Wen Tseng, Ping-Ching Wu, Ying-Chih Pu
A graphene quantum dot (GQD) used as the photosensitizer with high two-photon absorption in the near-infrared region, a large absolute cross section of two-photon excitation (TPE), strong two-photon luminescence and impressive two-photon stability could be used for dual modality two-photon photodynamic therapy (PDT) and two-photon bioimaging with an ultrashot pulse laser (or defined as TPE). In this study, a GQD efficiently generated reactive oxygen species coupled with TPE, which highly increased the effective PDT ability of both gram-positive and -negative bacteria, with ultra-low energy and an extremely short photoexcitation time generated by TPE...
October 18, 2016: ACS Applied Materials & Interfaces
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