| 1. |
- Fröhlich, Christopher, et al.
(författare)
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Structural and biochemical characterization of the environmental MBLs MYO-1, ECV-1 and SHD-1.
- 2020
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Ingår i: The Journal of antimicrobial chemotherapy. - : Oxford University Press (OUP). - 1460-2091 .- 0305-7453. ; 75:9, s. 2554-2563
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Tidskriftsartikel (refereegranskat)abstract
- MBLs form a large and heterogeneous group of bacterial enzymes conferring resistance to β-lactam antibiotics, including carbapenems. A large environmental reservoir of MBLs has been identified, which can act as a source for transfer into human pathogens. Therefore, structural investigation of environmental and clinically rare MBLs can give new insights into structure-activity relationships to explore the role of catalytic and second shell residues, which are under selective pressure.To investigate the structure and activity of the environmental subclass B1 MBLs MYO-1, SHD-1 and ECV-1.The respective genes of these MBLs were cloned into vectors and expressed in Escherichia coli. Purified enzymes were characterized with respect to their catalytic efficiency (kcat/Km). The enzymatic activities and MICs were determined for a panel of different β-lactams, including penicillins, cephalosporins and carbapenems. Thermostability was measured and structures were solved using X-ray crystallography (MYO-1 and ECV-1) or generated by homology modelling (SHD-1).Expression of the environmental MBLs in E. coli resulted in the characteristic MBL profile, not affecting aztreonam susceptibility and decreasing susceptibility to carbapenems, cephalosporins and penicillins. The purified enzymes showed variable catalytic activity in the order of <5% to ∼70% compared with the clinically widespread NDM-1. The thermostability of ECV-1 and SHD-1 was up to 8°C higher than that of MYO-1 and NDM-1. Using solved structures and molecular modelling, we identified differences in their second shell composition, possibly responsible for their relatively low hydrolytic activity.These results show the importance of environmental species acting as reservoirs for MBL-encoding genes.
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| 2. |
- Gudmundsdottir, Jonina S., et al.
(författare)
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The chemotherapeutic drug methotrexate selects for antibiotic resistance
- 2021
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Ingår i: EBioMedicine. - : Elsevier. - 2352-3964. ; 74
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Tidskriftsartikel (refereegranskat)abstract
- Background: Understanding drivers of antibiotic resistance evolution is fundamental for designing optimal treatment strategies and interventions to reduce the spread of antibiotic resistance. Various cytotoxic drugs used in cancer chemotherapy have antibacterial properties, but how bacterial populations are affected by these selective pressures is unknown. Here we test the hypothesis that the widely used cytotoxic drug methotrexate affects the evolution and selection of antibiotic resistance.Methods: First, we determined methotrexate susceptibility (IC90) and selective abilities in a collection of Escherichia coli and Klebsiella pneumoniae strains with and without pre-existing trimethoprim resistance determinants. We constructed fluorescently labelled pairs of E. coli MG1655 differing only in trimethoprim resistance determinants and determined the minimum selective concentrations of methotrexate using flow-cytometry. We further used an experimental evolution approach to investigate the effects of methotrexate on de novo trimethoprim resistance evolution.Findings: We show that methotrexate can select for acquired trimethoprim resistance determinants located on the chromosome or a plasmid. Additionally, methotrexate co-selects for genetically linked resistance determinants when present together with trimethoprim resistance on a multi-drug resistance plasmid. These selective effects occur at concentrations 40- to >320-fold below the methotrexate minimal inhibitory concentration.Interpretation: Our results strongly suggest a selective role of methotrexate for virtually any antibiotic resistance determinant when present together with trimethoprim resistance on a multi-drug resistance plasmid. The presented results may have significant implications for patient groups strongly depending on effective antibiotic treatment.
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| 3. |
- Karah, Nabil, et al.
(författare)
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CRISPR-cas subtype I-Fb in Acinetobacter baumannii : evolution and utilization for strain subtyping
- 2015
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- Clustered regularly interspaced short palindromic repeats (CRISPR) are polymorphic elements found in the genome of some or all strains of particular bacterial species, providing them with a system of acquired immunity against invading bacteriophages and plasmids. Two CRISPR-Cas systems have been identified in Acinetobacter baumannii, an opportunistic pathogen with a remarkable capacity for clonal dissemination. In this study, we investigated the mode of evolution and diversity of spacers of the CRISPR-cas subtype I-Fb locus in a global collection of 76 isolates of A. baumannii obtained from 14 countries and 4 continents. The locus has basically evolved from a common ancestor following two main lineages and several pathways of vertical descent. However, this vertical passage has been interrupted by occasional events of horizontal transfer of the whole locus between distinct isolates. The isolates were assigned into 40 CRISPR-based sequence types (CST). CST1 and CST23-24 comprised 18 and 9 isolates, representing two main sub-clones of international clones CC1 and CC25, respectively. Epidemiological data showed that some of the CST1 isolates were acquired or imported from Iraq, where it has probably been endemic for more than one decade and occasionally been able to spread to USA, Canada, and Europe. CST23-24 has shown a remarkable ability to cause national outbreaks of infections in Sweden, Argentina, UAE, and USA. The three isolates of CST19 were independently imported from Thailand to Sweden and Norway, raising a concern about the prevalence of CST19 in Thailand. Our study highlights the dynamic nature of the CRISPR-cas subtype I-Fb locus in A. baumannii, and demonstrates the possibility of using a CRISPR-based approach for subtyping a significant part of the global population of A. baumannii.
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| 4. |
- Karah, Nabil, et al.
(författare)
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Plasmid-mediated quinolone resistance determinants qnr and aac(6')-Ib-cr in Escherichia coli and Klebsiella spp. from Norway and Sweden
- 2010
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Ingår i: Diagnostic microbiology and infectious disease. - : Elsevier BV. - 0732-8893 .- 1879-0070. ; 66:4, s. 425-431
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Tidskriftsartikel (refereegranskat)abstract
- The prevalence of the plasmid-mediated quinolone resistance genes qnr and aac(6')-Ib-cr was investigated among clinical isolates of Escherichia coli and Klebsiella spp. selected from 2 collections of consecutive isolates collected in 2004 to 2005 in Norway (n = 2479) and Sweden (n = 2980) and 1 group of extended-spectrum beta-lactamase (ESBL)-producing isolates collected in 2003 in Norway (n = 71). A total of 414 isolates was selected for screening based on resistance to nalidixic acid and/or reduced susceptibility/resistance to ciprofloxacin. The prevalence of both qnr and aac(6')-Ib-cr was higher among the ESBL producers (9.1% and 52.3%, respectively) than in the consecutive isolates (1.1% and 3.2%, respectively). qnrS1 was detected in 6 isolates, whereas qnrB1 and qnrB7 were detected in 2 isolates. The genetic structure surrounding qnrS1 was similar to previously described structures. In 2 isolates, qnrS1 was located on conjugative IncN-type plasmids of approximately 140 kb.
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| 5. |
- Ljungquist, Oskar, et al.
(författare)
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Nationwide, population-based observational study of the molecular epidemiology and temporal trend of carbapenemase-producing Enterobacterales in Norway, 2015 to 2021
- 2023
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Ingår i: Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin. - 1560-7917. ; 28:27, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- IntroductionNational and regional carbapenemase-producing Enterobacterales (CPE) surveillance is essential to understand the burden of antimicrobial resistance, elucidate outbreaks, and develop infection-control or antimicrobial-treatment recommendations.AimThis study aimed to describe CPE and their epidemiology in Norway from 2015 to 2021.MethodsA nationwide, population-based observational study of all verified clinical and carriage CPE isolates submitted to the national reference laboratory was conducted. Isolates were characterised by antimicrobial susceptibility testing, whole genome sequencing (WGS) and basic metadata. Annual CPE incidences were also estimated.ResultsA total of 389 CPE isolates were identified from 332 patients of 63 years median age (range: 0-98). These corresponded to 341 cases, 184 (54%) being male. Between 2015 and 2021, the annual incidence of CPE cases increased from 0.6 to 1.1 per 100,000 person-years. For CPE-isolates with available data on colonisation/infection, 58% (226/389) were associated with colonisation and 38% (149/389) with clinical infections. WGS revealed a predominance of OXA-48-like (51%; 198/389) and NDM (34%; 134/389) carbapenemases in a diversified population of Escherichia coli and Klebsiella pneumoniae, including high-risk clones also detected globally. Most CPE isolates were travel-related (63%; 245/389). Although local outbreaks and healthcare-associated transmission occurred, no interregional spread was detected. Nevertheless, 18% (70/389) of isolates not directly related to import points towards potentially unidentified transmission routes. A decline in travel-associated cases was observed during the COVID-19 pandemic.ConclusionsThe close-to-doubling of CPE case incidence between 2015 and 2021 was associated with foreign travel and genomic diversity. To limit further transmission and outbreaks, continued screening and monitoring is essential.
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| 6. |
- Lofton Tomenius, Hava, 1976-
(författare)
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Mechanisms and Biological Costs of Bacterial Resistance to Antimicrobial Peptides
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The global increasing problem of antibiotic resistance necessarily drives the pursuit and discovery of new antimicrobial agents. Antimicrobial peptides (AMPs) initially seemed like promising new drug candidates. Already members of the innate immune system, it was assumed that they would be bioactive and non-toxic. Their common trait for fundamental, non-specific mode of action also seemed likely to reduce resistance development.In this thesis, we demonstrate the ease with which two species of pathogenic bacteria, the gram-negative Salmonella typhimurium (S. typhimurium), and the gram-positive Staphylococcus aureus (S. aureus), can gain increased tolerance and stable resistance to various AMPs. By serially passaging each bacterial species separately under increasing AMP selection pressure we observed increasing AMP tolerance. Resulting in independent bacterial lineages exposed to four different AMPs (including a two-AMP combination) that exhibited 2 to 16-fold increases in MIC. Substantial cross-resistance between the AMPs was observed. Additionally, the S. aureus mutants were found to be cross-resistant to human beta-defensins 1, 2, 3, and 4.The LPS molecule, with mutations in the waaY, pmrB and phoP genes, was the principal target for S. typhimurium resistance development. The main target for S. aureus remained elusive. Reduced membrane potential was a common change for two of the mutants, but not for the others. All sequenced mutants had one or more mutations in various stress response pathways.Fitness of the resistant mutants was assayed by growth rate analysis and in vitro virulence factor testing (e.g. survival response to bile, superoxide, acidic pH). Furthermore an in vivo survival/virulence test involving a mouse competition experiment (S. typhimurium) and sepsis model (S. aureus) was performed. In the absence of AMPs there was often little or no fitness reduction in the mutants. Our results suggest that AMP resistance mechanisms do not irrevocably weaken either species with regard to virulence characteristics or survival within the host.In light of these findings, we suggest that the progression of therapeutic use of AMPs should proceed with great caution since otherwise we might select for AMP resistant mutants that are more resistant to our innate host defenses and thereby potentially more virulent.
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| 7. |
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| 8. |
- Vik, Anders, et al.
(författare)
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Antimicrobial and cytotoxic activity of agelasine and agelasimine analogs
- 2007
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Ingår i: Bioorganic & Medicinal Chemistry. - : Elsevier BV. - 0968-0896 .- 1464-3391. ; 15:12, s. 4016-4037
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Tidskriftsartikel (refereegranskat)abstract
- Agelasine and agelasimine derivatives with substantially less complicated terpenoid side chains compared to the naturally occurring compounds have been synthesized and their ability to inhibit growth of microorganisms and cancer cells has been studied. Compounds with excellent activity against cancer cell lines (MIC ca. 1 μM for the most potent compounds), including a drug resistant renal cell line, have been identified. Most compounds studied also exhibited broad spectrum antimicrobial activity including activity against Mycobacterium tuberculosis.
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