| 1. |
- Allander, Lisa
(författare)
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β-lactam combinations against multidrug-resistant Enterobacterales : Exploring combination effects and resistance development
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The β-lactam antibiotics are a cornerstone in treating bacterial infections, but the increasing prevalence of antibiotic resistance worldwide threatens their effectiveness. The main driver of β-lactam resistance is the production of β-lactamases, which are bacterial enzymes that inactivate the antibiotic. Moreover, resistance to multiple antibiotic classes is common in β-lactamase producing bacteria, further limiting treatment options. At the same time, few novel antibacterial agents are reaching the market. To address this challenge, antibiotic combination therapy is employed to enhance the effects of existing drugs against multidrug-resistant bacteria. Yet, there is a lack of knowledge regarding which antibiotics to combine to achieve the best effect. The investigations in this thesis evaluate the potential and limitations of combinations involving β-lactams, β-lactamase inhibitors and colistin against multidrug-resistant Enterobacterales in vitro. In the first paper, we investigated resistance mechanisms to three commonly used β-lactam/β-lactamase inhibitor combinations (BLBLIs) in an Escherichia coli strain encoding multiple β-lactamases. We found that β-lactamase gene amplifications were a key driver of resistance, with variations in the amplification pattern depending on the BLBLI combination. Clinical resistance could be reached by gene amplifications for ampicillin-sulbactam and piperacillin-tazobactam, whereas ceftazidime-avibactam resistance required multiple genetic changes. In the second paper, we evaluated the efficacy of double-carbapenem combinations against E. coli and Klebsiella pneumoniae producing carbapenemases (KPC-2, OXA-48, NDM-1, and NDM-5). Synergistic effects were most commonly observed against OXA-48-producing strains, whereas the efficacy was low against KPC-2 and negligible against NDM producers. In the third and fourth papers, we evaluated the antibacterial activity of colistin in combination with BLBLIs. Considering that reduced membrane permeability is associated with decreased susceptibility towards BLBLIs, adding colistin may be beneficial since its membrane-disrupting effect may increase the entry of other drugs. In paper three, we showed synergistic effects with colistin and ceftazidime-avibactam against a KPC-2-producing K. pneumoniae strain with porin deficiencies. However, when systematically assessing the impact of porin loss on the synergistic potential of colistin in combination with BLBLIs in paper four, we did not find any clear association between porin loss and synergy. These studies provide insight into the therapeutic potential and limitations of combinations, including β-lactam antibiotics against strains with different setups of resistance genes. More research is required to understand how to best use the newly introduced BLBLI combinations to preserve their activity and enhance the value of the available antibiotics for future generations.
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| 2. |
- Bengtsson, Stina, et al.
(författare)
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Sequence types and plasmid carriage of uropathogenic Escherichia coli devoid of phenotypically detectable resistance
- 2012
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Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 67:1, s. 69-73
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Tidskriftsartikel (refereegranskat)abstract
- Objectives Plasmids play a major role in the dissemination of antibiotic resistance, and several studies have shown the association between specific resistance mechanisms and certain plasmid types and/or Escherichia coli lineages. This study describes the distribution of plasmids, replicon types, sequence types (STs) and ST complexes (STCs) of E. coli devoid of phenotypic resistance to 24 antibiotics. Methods Eighty E. coli isolates from urinary tract infections from four European countries were selected because of their lack of phenotypically detectable antibiotic resistance. The isolates were characterized to the phylogenetic group level using PCR and to ST by multilocus sequence typing. Plasmid carriage was assessed using S1 nuclease PFGE profiling and PCR-based replicon typing. Results Plasmids were detected in only 38/80 (47%) of the isolates; one (n = 18), two (n = 14), three (n = 5) and four (n = 1) plasmids. Six different replicon types were identified, the most common being a combination of IncFII and IncFIB. Most isolates belonged to phylogenetic group B2 and STC73 (n = 20), STC95 (n = 7) and ST420 (n = 6). A high proportion of STC73 isolates (75%) was devoid of plasmids. No association could be found between specific STs and replicon type. Conclusions A large proportion of E. coli strains phenotypically devoid of antibiotic resistance were plasmid naive. Those isolates that harboured plasmids displayed replicon types similar to those of resistant isolates, but the distributions of STs and STCs were different. This may indicate chromosomally encoded mechanisms important for the stabilization of plasmids harbouring antibiotic resistance.
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| 3. |
- Bjørkeng, Eva, et al.
(författare)
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Clustering of polyclonal VanB-type vancomycin-resistant Enterococcus faecium in a low-endemic area was associated with CC17-genogroup strains harbouring transferable vanB2-Tn5382 and pRUM-like repA containing plasmids with axe-txe plasmid addiction systems
- 2011
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Ingår i: Acta Pathologica, Microbiologica et Immunologica Scandinavica (APMIS). - : Wiley-Blackwell. - 0903-4641 .- 1600-0463. ; 119:4-5, s. 247-258
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Tidskriftsartikel (refereegranskat)abstract
- VanB-type vancomycin-resistant Enterococcus faecium isolates (n = 17) from 15 patients at the Örebro University hospital in Sweden during a span of 18 months was characterized. All patients had underlying disorders and received broad-spectrum antimicrobial therapy. Pulsed-field gel electrophoresis (PFGE) grouped 14 isolates in three PFGE types and three isolates in unique PFGE patterns. All isolates had multi-locus sequence types [ST17 (n = 5); ST18 (n = 3); ST125 (n = 7); ST262 (n = 1); ST460 (n = 1)] belonging to the successful hospital-adapted clonal complex 17 (CC17), harboured CC17-associated virulence genes, were vanB2-positive and expressed diverse vancomycin minimum inhibitory concentration (MICs; 8 to > 256 mg/L). Isolate 1 had a unique PFGE type and a chromosomal transferable vanB2-Tn5382 element. Interestingly, the other five PFGE types had Tn5382 located on plasmids containing pRUM-like repA and a plasmid addiction system (axe-txe) shown by co-hybridization analysis of PFGE-separated S1-nuclease digested total DNA. The resistance plasmids were mainly of 120-kb and supported intraspecies vanB transfer. Two strains were isolated from patient 6 and we observed a possible transfer of the vanB2-resistance genes from PFGE type III ST460 to a more successful PFGE type I ST125. This latter PFGE type I ST125 became the predominant type afterwards. Our observations support the notion that vanB-type vancomycin-resistant Enterococcus faecium can persist in a low-endemic area through successful clones and plasmids with stability functions in hospital patients with known risk factors.
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| 4. |
- Crowe-McAuliffe, Caillan, et al.
(författare)
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Structural basis for PoxtA-mediated resistance to phenicol and oxazolidinone antibiotics
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- PoxtA and OptrA are ATP binding cassette (ABC) proteins of the F subtype (ABCF). They confer resistance to oxazolidinone and phenicol antibiotics, such as linezolid and chloramphenicol, which stall translating ribosomes when certain amino acids are present at a defined position in the nascent polypeptide chain. These proteins are often encoded on mobile genetic elements, facilitating their rapid spread amongst Gram-positive bacteria, and are thought to confer resistance by binding to the ribosome and dislodging the bound antibiotic. However, the mechanistic basis of this resistance remains unclear. Here we refine the PoxtA spectrum of action, demonstrate alleviation of linezolid-induced context-dependent translational stalling, and present cryo-electron microscopy structures of PoxtA in complex with the Enterococcus faecalis 70S ribosome. PoxtA perturbs the CCA-end of the P-site tRNA, causing it to shift by ∼4 Å out of the ribosome, corresponding to a register shift of approximately one amino acid for an attached nascent polypeptide chain. We postulate that the perturbation of the P-site tRNA by PoxtA thereby alters the conformation of the attached nascent chain to disrupt the drug binding site.
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| 5. |
- Hällgren, Anita, 1963-
(författare)
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Enterococci in Swedish intensive care units : studies on epidemiology, mechanisms of antibiotic resistance and virulence factors
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this thesis was to study enterococci in Sweden, their resistance to antibiotics in general and high-level gentamicin resistance (HLGR) in particular, with a special focus on the ICU setting. Dynamics of rectal colonisation during prolonged intensive care unit (ICU) stay was assessed. In addition, enterococcal virulence factors and the ability to adhere to abiotic surfaces such as urinary catheters were studied.We found that among prolonged-stay patients admitted to ICUs, the rectal flora was altered, with a decrease in Gram-negative rods in favour of Gram-positive bacteria, mainly Coagulase negative staphylococci and enterococci.Among clinical enterococcal isolates from patients admitted to Swedish ICUs, although vancomycin resistant enterococci (VRE) were only sporadically found, multidrug resistance was common. This was most apparent in Enterococcus faecium, where the majority of isolates were ampicillin- and quinolone resistant. Enterococcus faecalis was still the most frequently isolated enterococcal species in clinical specimens. Among patients admitted to Swedish ICUs 1996-1998, E. faecalis with HLGR was found in higher frequency (20%) than previously reported. The majority (89%) of these isolates belonged to two dominating clusters of genetically related E. faecalis. Cluster I (69%), which was predominantly found in the eastern and central parts of southern Sweden and Cluster II (20%) in south-western Sweden.In the County of Östergötland, the first E. faecalis with HLGR isolated from blood cultures was found in 1996. The yearly incidence of isolates with HLGR in E. faecalis bacteraemia was studied from 1996-2001, and varied between 9-22%. The majority of these isolates were genetically related and belonged to Cluster I, also found in the previous study. The first blood isolate of E. faecium with HLGR in the County of Östergötland was found in 1999. A clone of E. faecium, with HLGR and ampicillin resistance, was found to colonise 6/10 and 2/11 prolonged-stay patients admitted from November 2001 through January 2002 to the general ICU and cardio-thoracic ICU, respectively, at the University Hospital of Linköping.All studied isolates with HLGR carried the gene aac(6')-Ie-aph(2'')-Ia encoding the bifunctional aminoglycoside modifying enzyme Aac(6')Ie-Aph(2'')Ia, which conveys resistance to all commercially available amino-glycosides except streptomycin. The location of the gene, aac(6')Ie-aph(2'')-Ia, was studied in 45 E. faecalis isolates and the gene was carried on a Tn5281-like transposon in all isolates except one. The 30 µg disc diffusion test, as recommended by the SRGA, had 100% sensitivity and specificity when compared to PCR detection of aac(6')-Ie-aph(2'')-Ia.E. faecalis isolates with HLGR belonging to widely disseminated clusters of genetically related isolates were more likely to carry both the gene encoding enterococcal surface protein (esp) and the gene encoding aggregation substance (asa1) compared to unique isolates. Esp was the only virulence factor found among E. faecium isolates, where it was common. E. faecalis isolates adhered with higher bacterial densities to urinary tract catheters compared to E. faecium isolates. In vitro adherence to urinary tract catheters was not affected by esp.
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| 6. |
- 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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| 7. |
- 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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| 8. |
- Samuelsen, Orjan, et al.
(författare)
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Molecular Epidemiology of Metallo-beta-Lactamase-Producing Pseudomonas aeruginosa Isolates from Norway and Sweden Shows Import of International Clones and Local Clonal Expansion
- 2010
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Ingår i: Antimicrobial Agents and Chemotherapy. - 1098-6596. ; 54:1, s. 346-352
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Tidskriftsartikel (refereegranskat)abstract
- Scandinavia is considered a region with a low prevalence of antimicrobial resistance. However, the number dof multidrug-resistant (MDR) Gram-negative bacteria is increasing, including metallo-beta-lactamase (MBL)-producing Pseudomonas aeruginosa. In this study MBL-producing P. aeruginosa isolates identified in Norway (n = 4) and Sweden (n = 9) from 1999 to 2007 were characterized. Two international clonal complexes (CC), CC111 (n = 8) and CC235 (n = 2), previously associated with MBL-producing isolates, were dominant. CC111 isolates (ST111/229; serotype O12; bla(VIM-2)) included clonally related isolates identified in Skane County, Sweden (n = 6), and two isolates associated with importation from Greece and Denmark. In all CC111 isolates, bla(VIM-2) was located in integron In59.2 or In59 variants. The two CC235 isolates (ST235/ST230; serotype O11; bla(VIM-4)) were imported from Greece and Cyprus, were possibly clonally related, and carried bla(VIM-4) in two different integron structures. Three isolates imported from Ghana (ST233; serotype O6; bla(VIM-2)), Tunisia (ST654; serotype O11; bla(VIM-2)), and Thailand (ST260; serotype O6; bla(IMP-14)) were clonally unrelated. ST233 was part of a new CC (CC233) that included other MBL-producing isolates, while ST654 could also be part of a new CC associated with MBL producers. In the isolates imported from Ghana and Tunisia, bla(VIM-2) was part of unusual integron structures lacking the 3' conserved segment and associated with transposons. The bla(VIM) gene was found to be located on the chromosome in all isolates. Known risk factors for acquisition of MBL were reported for all patients except one. The findings suggest that both import of successful international clones and local clonal expansion contribute to the emergence of MBL-producing P. aeruginosa in Scandinavia.
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| 9. |
- Sundqvist, Martin, 1974-, et al.
(författare)
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Within-Population Distribution of Trimethoprim Resistance in Escherichia coli before and after a Community-Wide Intervention on Trimethoprim Use
- 2014
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Ingår i: Antimicrobial Agents and Chemotherapy. - : American Society for Microbiology. - 0066-4804 .- 1098-6596. ; 58:12, s. 7492-7500
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Tidskriftsartikel (refereegranskat)abstract
- A 2-year prospective intervention on the prescription of trimethoprim reduced the use by 85% in a health care region with 178,000 inhabitants. Here, we performed before-and-after analyses of the within-population distribution of trimethoprim resistance in Escherichia coli. Phylogenetic and population genetic methods were applied to multilocus sequence typing data of 548 consecutively collected E. coli isolates from clinical urinary specimens. Results were analyzed in relation to antibiotic susceptibility and the presence and genomic location of different trimethoprim resistance gene classes. A total of 163 E. coli sequence types (STs) were identified, of which 68 were previously undescribed. The isolates fell into one of three distinct genetic clusters designated BAPS 1 (E. coli phylogroup B2), BAPS 2 (phylogroup A and B1), and BAPS 3 (phylogroup D), each with a similar frequency before and after the intervention. BAPS 2 and BAPS 3 were positively and BAPS 1 was negatively associated with trimethoprim resistance (odds ratios of 1.97, 3.17, and 0.26, respectively). In before-and-after analyses, trimethoprim resistance frequency increased in BAPS 1 and decreased in BAPS 2. Resistance to antibiotics other than trimethoprim increased in BAPS 2. Analysis of the genomic location of different trimethoprim resistance genes in isolates of ST69, ST58, and ST73 identified multiple independent acquisition events in isolates of the same ST. The results show that despite a stable overall resistance frequency in E. coli before and after the intervention, marked within-population changes occurred. A decrease of resistance in one major genetic cluster was masked by a reciprocal increase in another major cluster.
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| 10. |
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