• The fight to keep resistance at bay, epidemiology of carbapenemase producing organisms (CPOs), vancomycin resistant enterococci (VRE) and methicillin resistant Staphylococcus aureus (MRSA) in Norway, 2006-2017 

      Elstrøm, Petter; Astrup, Elisabeth; Hegstad, Kristin; Samuelsen, Ørjan; Enger, Hege; Kacelnik, Oliver (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-04)
      <p><i>Introduction - </i>Scandinavian countries have traditionally had a low prevalence of resistant organisms, but have in recent years experienced a change in their epidemiology. We aim to describe the epidemiology of carbapenemase-producing organisms (CPOs), vancomycin-resistant enterococci (VRE) and methicillin-resistant <i>S. aureus</i> (MRSA) in Norway, measure the importance of infections ...
    • Gastrointestinal carriage of Klebsiella pneumoniae in a general adult population: a cross-sectional study of risk factors and bacterial genomic diversity 

      Raffelsberger, Niclas Peter; Hetland, Marit Andrea Klokkhammer; Svendsen, Kristian; Småbrekke, Lars; Löhr, Iren Høyland; Andreassen, Lotte; Brisse, Sylvain; Holt, Kathryn E.; Sundsfjord, Arnfinn; Samuelsen, Ørjan; Gravningen, Kirsten Midttun (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-28)
      Antibiotic resistant <i>Klebsiella pneumoniae</i> is a leading public health threat and gastrointestinal carriage is an established risk factor for subsequent infections during hospitalization. Our study contributes new knowledge of risk factors for gastrointestinal carriage and the genomic population structure of <i>K. pneumoniae</i> colonizing humans in a representative sample of a general population ...
    • A high-throughput multiplexing and selection strategy to complete bacterial genomes 

      Alonso, Sergio Arredondo; Pöntinen, Anna K.; Cleon, Francois Pierre Alexandre; Gladstone, Rebecca Ashley; Schürch, Anita C.; Johnsen, Pål Jarle; Samuelsen, Ørjan; Corander, Jukka (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-09)
      Background: Bacterial whole-genome sequencing based on short-read technologies often results in a draft assembly formed by contiguous sequences. The introduction of long-read sequencing technologies permits those contiguous sequences to be unambiguously bridged into complete genomes. However, the elevated costs associated with long-read sequencing frequently limit the number of bacterial isolates ...
    • Horizontal plasmid transfer among klebsiella pneumoniae isolates is the key factor for dissemination of extended-spectrum β-lactamases among children in Tanzania 

      Pedersen, Torunn Annie; Tellevik, Marit Gjerde; Kommedal, Øyvind; Lindemann, Paul Christoffer; Moyo, Sabrina John; Janice, Jessin; Blomberg, Bjørn; Samuelsen, Ørjan; Langeland, Nina (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-07-15)
      Increased knowledge about the role of horizontal gene transfer is key to improve our understanding of the spread of antimicrobial resistance (AMR) in human populations. We therefore studied the dissemination of the <i>bla</i><sub>CTX-M-15</sub> extended-spectrum-β-lactamase (ESBL) gene in <i>Klebsiella pneumoniae</i> isolates obtained from stool samples from hospitalized children and healthy controls ...
    • Host dependent maintenance of a blaNDM-1-encoding plasmid in clinical Escherichia coli isolates 

      Alves Gama, Joao Pedro; Kloos, Julia Maria; Johnsen, Pål Jarle; Samuelsen, Ørjan (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-09)
      Dissemination of bacterial clones carrying plasmid-mediated resistance genes is a major factor contributing to the increasing prevalence of antibiotic resistance. Understanding the evolution of successful clones and the association to mobile resistance elements are therefore crucial. In this study, we determined the sequence of a 145 kb IncC multi-drug resistance plasmid (pK71-77-1-NDM), harbouring ...
    • Identification of VIM-2-producing Pseudomonas aeruginosa from Tanzania is associated with sequence types 244 and 640 and the location of blaVIM-2 in a TniC integron 

      Moyo, Sabrina John; Haldorsen, Bjørg; Aboud, Said; Blomberg, Bjørn; Maselle, Samuel Y; Sundsfjord, Arnfinn; Langeland, Nina; Samuelsen, Ørjan (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
    • Impact of extensive antibiotic treatment on faecal carriage of antibiotic-resistant enterobacteria in children in a low resistance prevalence setting 

      Knudsen, Per Kristian; Brandtzæg, Petter; Høiby, Ernst Arne; Bohlin, Jon; Samuelsen, Ørjan; Steinbakk, Martin; Abrahamsen, Tore G; Müller, Fredrik; Gammelsrud, Karianne Wiger (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-07)
      We prospectively studied the consequences of extensive antibiotic treatment on faecal carriage of antibiotic-resistant enterobacteria in a cohort of children with cystic fibrosis (CF) and a cohort of children with cancer compared to healthy children with no or low antibiotic exposure. The study was conducted in Norway in a low resistance prevalence setting. Sixty longitudinally collected faecal ...
    • Intracellular Transposition and Capture of Mobile Genetic Elements following Intercellular Conjugation of Multidrug Resistance Conjugative Plasmids from Clinical Enterobacteriaceae Isolates 

      Tansirichaiya, Supathep; Goodman, Richard N.; Guo, Xinyu; Bulgasim, Issra; Samuelsen, Ørjan; Al-Haroni, Mohammed; Roberts, Adam P. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-19)
      Mobile genetic elements (MGEs) are often associated with antimicrobial resistance genes (ARGs). They are responsible for intracellular transposition between different replicons and intercellular conjugation and are therefore important agents of ARG dissemination. Detection and characterization of functional MGEs, especially in clinical isolates, would increase our understanding of the underlying ...
    • Intraregional hospital outbreak of OXA-244-producing Escherichia coli ST38 in Norway, 2020 

      Lindemann, Paul Christoffer; Pedersen, Torunn Annie; Oma, Dorthea Hagen; Janice, Jessin; Grøvan, Fredrik; Chedid, Ghantous Milad; Hafne, Liv Jorunn; Josefsen, Ellen Haldis; Kacelnik, Oliver; Sundsfjord, Arnfinn; Samuelsen, Ørjan (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-06)
      Infections with OXA-244-carbapenemase-producing Escherichia coli with sequence type (ST)38 have recently increased in Europe. Due to its low-level activity against carbapenems, OXA-244 can be difficult to detect. Previous assessments have not revealed a clear source and route of transmission for OXA-244-producing E. coli, but there are indications of non-healthcare related sources and community ...
    • Investigating the role of residues W228 and Y233 in the structure and activity of the GIM-1 metallo-beta-lactamase. 

      Skagseth, Susann; Carlsen, Trine Josefine Olsen; Bjerga, Gro Elin Kjæreng; Spencer, James; Samuelsen, Ørjan; Leiros, Hanna-Kirsti S. (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-07)
      Metallo--lactamases (MBLs) hydrolyze virtually all -lactam antibiotics, including penicillins, cephalosporins, and carbapenems. The worldwide emergence of antibiotic-resistant bacteria harboring MBLs poses an increasing clinical threat. The MBL German imipenemase-1 (GIM-1) possesses an active site that is narrower and more hydrophobic than the active sites of other MBLs. The GIM-1 active-site ...
    • A Long-Term Low-Frequency Hospital Outbreak of KPC-Producing Klebsiella pneumoniae Involving Intergenus Plasmid Diffusion and a Persisting Environmental Reservoir 

      Tofteland, Ståle; Naseer, Mohammed Umaer; Lislevand, Jan Helge; Sundsfjord, Arnfinn; Samuelsen, Ørjan (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Background: To study the molecular characteristics of a long-term, low frequency outbreak of blaKPC-2 in a low prevalence setting involving the hospital environment. Methodology/Principal Findings: KPC-producing bacteria were screened by selective chromogenic agar and Real-Time PCR. The presence of antibiotic resistance genes was ascribed by PCRs and subsequent sequencing, and the KPC-producing isolates ...
    • Metallo-β-lactamase inhibitors by bioisosteric replacement: preparation, activity and binding 

      Skagseth, Susann; Akhter, Sundus; Paulsen, Marianne H; Muhammad, Zeeshan; Samuelsen, Ørjan; Leiros, Hanna-Kirsti S.; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-14)
      Bacterial resistance is compromising the use of β-lactam antibiotics including carbapenems. The main resistance mechanism against β-lactams is hydrolysis of the β-lactam ring mediated by serine- or metallo-β-lactamases (MBLs). Although several inhibitors of MBLs have been reported, none has been developed into a clinically useful inhibitor. Mercaptocarboxylic acids are among the most prominent ...
    • Mge-cluster: a reference-free approach for typing bacterial plasmids 

      Alonso, Sergio Arredondo; Gladstone, Rebecca Ashley; Pöntinen, Anna Kaarina; Gama, João Alves; Schürch, Anita C.; Lanza, Val F.; Johnsen, Pål Jarle; Samuelsen, Ørjan; Tonkin-Hill, Gerry; Corander, Jukka (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-10)
      Extrachromosomal elements of bacterial cells such as plasmids are notorious for their importance in evolution and adaptation to changing ecology. However, high-resolution population-wide analysis of plasmids has only become accessible recently with the advent of scalable long-read sequencing technology. Current typing methods for the classification of plasmids remain limited in their scope which ...
    • Molecular and epidemiological characterization of carbapenemase-producing Enterobacteriaceae in Norway, 2007 to 2014 

      Samuelsen, Ørjan; Overballe-Petersen, Søren; Bjørnholt, Jørgen; Brisse, Sylvain; Doumith, Michel; Woodford, Neil; Hopkins, Katie L.; Aasnæs, Bettina; Haldorsen, Bjørg; Sundsfjord, Arnfinn (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-15)
      The prevalence of carbapenemase-producing Enterobacteriaceae (CPE) is increasing worldwide. Here we present associated patient data and molecular, epidemiological and phenotypic characteristics of all CPE isolates in Norway from 2007 to 2014 confirmed at the Norwegian National Advisory Unit on Detection of Antimicrobial Resistance. All confirmed CPE isolates were characterized pheno- and genotypically, ...
    • A nationwide genomic study of clinical Klebsiella pneumoniae in Norway 2001–15: introduction and spread of ESBLs facilitated by clonal groups CG15 and CG307 

      Fostervold, Aasmund; Hetland, Marit Andrea Klokkhammer; Bakksjø, Ragna-Johanne; Bernhoff, Eva; Holt, Kathryn E.; Samuelsen, Ørjan; Simonsen, Gunnar Skov; Sundsfjord, Arnfinn; Wyres, Kelly L.; Löhr, Iren Høyland (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-22)
      Objectives: To use the nationwide Norwegian surveillance programme on resistant microbes in humans (NORM) to address longitudinal changes in the population structure of Klebsiella pneumoniae isolates from 2001–15, focusing on the emergence and dissemination of ESBL-producing K. pneumoniae in Norway.<p> <p>Methods: Among blood (n = 6124) and urinary tract (n = 5496) surveillance isolates from ...
    • Nationwide, population-based observational study of the molecular epidemiology and temporal trend of carbapenemase-producing Enterobacterales in Norway, 2015 to 2021 

      Ljungquist, Oskar; Haldorsen, Bjørg; Pöntinen, Anna Kaarina; Janice, Jessin; Josefsen, Ellen Haldis; Elstrøm, Petter; Kacelnik, Oliver; Sundsfjord, Arnfinn; Samuelsen, Ørjan; Handal, Nina; Ranheim, Trond Egil; Hansen, Bent-Are; Mjøen, Andreas Fossum; Lindemann, Paul Christoffer; Nilsen, Einar; Zaragkoulias, Kyriakos; Larsen, Hege Elisabeth; Bjørnholt, Jørgen; Gammelsrud, Karianne Wiger; Jakovljev, Aleksandra; Löhr, Iren Høyland; Bredberg, Anders; Marvik, Åshild; Minge, Christina; Tofteland, Ståle; Papp, Kristina; Onken, Annette; Weme, Einar Tollaksen; Guennigsman, Brian Albert (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-06)
      National and regional carbapenemaseproducing Enterobacterales (CPE) surveillance is essential to understand the burden of antimicrobial resistance, elucidate outbreaks, and develop infection-control or antimicrobial-treatment recommendations. Aim: This study aimed to describe CPE and their epidemiology in Norway from 2015 to 2021. Methods: A nationwide, population-based observational study of ...
    • OXA-48-Mediated Ceftazidime-Avibactam Resistance Is Associated with Evolutionary Trade-Offs 

      Fröhlich, Christopher; Sørum, Vidar; Thomassen, Ane Molden; Johnsen, Pål Jarle; Samuelsen, Ørjan (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-27)
      Infections due to carbapenemase-producing Gram-negative pathogens are associated with limited treatment options and consequently lead to increased mortality and morbidity. In response, combinations of existing β-lactams and novel β-lactamase inhibitors, such as ceftazidime-avibactam (CAZ-AVI), have been developed as alternative treatment options. To understand the development of resistance and ...
    • Performance of the EUCAST disc diffusion method and two MIC methods in detection of Enterobacteriaceae with reduced susceptibility to meropenem: the NordicAST CPE study. 

      Haldorsen, Bjørg; Giske, Christian G; Hansen, Dennis S; Helgason, Kristjan Orri; Kahlmeter, Gunnar; Löhr, Iren Høyland; Matuschek, Erika; Österblad, Monica; Rantakokko-Jalava, Kaisu; Wang, Mikala; Småbrekke, Lars; Samuelsen, Ørjan; Sundsfjord, Arnfinn (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-24)
      Objectives: To examine performance of EUCAST disc diffusion and supplementary MIC methods for detection of Enterobacteriaceae with reduced susceptibility to meropenem using EUCAST screening recommendations.<p> <p>Methods: Sixty-one Nordic laboratories delivered data on EUCAST disc diffusion (n " 61), semi-automated meropenem MIC (n " 23; VITEK2, n " 20 and Phoenix, n " 3) and gradient meropenem ...
    • Pharmacokinetics and pharmacodynamics of fosfomycin and its activity against extended-spectrum-lactamase-, plasmid-mediated AmpC-, and carbapenemase-producing escherichia coli in a murine urinary tract infection model 

      Zykov, Ilya Nikolaevich; Samuelsen, Ørjan; Jakobsen, Lotte; Småbrekke, Lars; Andersson, Dan I.; Sundsfjord, Arnfinn; Frimodt-Møller, Niels (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-25)
      Fosfomycin has become an attractive treatment alternative for urinary tract infections (UTIs) due to increasing multidrug resistance (MDR) in <i>Escherichia coli</i>. In this study, we evaluated the pharmacokinetic (PK) and pharmacodynamic (PD) indices of fosfomycin and its <i>in vivo</i> activity in an experimental murine model of ascending UTI. Subcutaneous administration of fosfomycin showed that ...
    • Phenotypic and genotypic characterisation of thymine auxotrophy in Escherichia coli isolated from a patient with recurrent bloodstream infection 

      Jakovljev, Aleksandra; Afset, Jan Egil; Haugum, Kjersti; Steinum, Harald Otto; Rønning, Torunn Gresdal; Samuelsen, Ørjan; Ås, Christina Gabrielsen (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-08)
      Introduction<p> <p>Thymine auxotrophic in vitro mutants of Escherichia coli were first reported in the mid-20th century. Later, thymine-dependent clinical strains of E. coli as well as other Enterobacterales, Enterococcus faecalis and Staphylococcus aureus have been recognized as the cause of persistent and recurrent infections. <p>Objectives <p>The aim of this study was to characterize the ...