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| 2. |
- Kivi, Marten, et al.
(författare)
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Helicobacter pylori genome variability in a framework of familial transmission
- 2007
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Ingår i: BMC Microbiology. - : Springer Science and Business Media LLC. - 1471-2180. ; 7, s. 54-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Helicobacter pylori infection is exceptionally prevalent and is considered to be acquired primarily early in life through person-to-person transmission within the family. H. pylori is a genetically diverse bacterial species, which may facilitate adaptation to new hosts and persistence for decades. The present study aimed to explore the genetic diversity of clonal isolates from a mother and her three children in order to shed light on H. pylori transmission and host adaptation. Results: Two different H. pylori strains and strain variants were identified in the family members by PCR-based molecular typing and sequencing of five loci. Genome diversity was further assessed for 15 isolates by comparative microarray hybridizations. The microarray consisted of 1,745 oligonucleotides representing the genes of two previously sequenced H. pylori strains. The microarray analysis detected a limited mean number (+/- standard error) of divergent genes between clonal isolates from the same and different individuals (1 +/- 0.4, 0.1%, and 3 +/- 0.3, 0.2%, respectively). There was considerable variability between the two different strains in the family members (147 +/- 4, 8%) and for all isolates relative to the two sequenced reference strains (314 +/- 16, 18%). The diversity between different strains was associated with gene functional classes related to DNA metabolism and the cell envelope. Conclusion: The present data from clonal H. pylori isolates of family members do not support that transmission and host adaptation are associated with substantial sequence diversity in the bacterial genome. However, important phenotypic modifications may be determined by additional genetic mechanisms, such as phase-variation. Our findings can aid further exploration of H. pylori genetic diversity and adaptation.
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| 3. |
- Lundin, Annelie
(författare)
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Diversity and persistence of Helicobacter pylori
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Helicobacter pylori is an exceptionally diverse bacterial species, and every infected individual harbors a unique strain, apart from the strain concordance found in some families. The infection is usually acquired during childhood and once established, persists for life unless treated with antibiotics. When infecting a new host, the bacterium causes inflammation in the gastric lining, which in most cases is asymptomatic, but may progress to chronic gastritis, gastric or duodenal ulcers or gastric cancer. We have performed extensive genetic analyses of H. pylori to give further insight in this immense diversity with a focus on the cytotoxin associated gene pathogenicity island (cag PAI), encoding a type IV secretion system (TFSS). First we studied two subclones, one cag PAI positive and one negative, isolated from the same biopsy. These isolates differed genetically, as determined by microarray genotyping, but were more similar to each other than to any other analyzed strain. In addition, both subclones colonized germ-free transgenic Lewis B expressing mice to an equal density, but the cag PAI negative strain did not colonize conventionally raised mice, while the cag PAI positive did. Investigating reisolates from mice infected for up to 10 months with the cag PAI positive strain revealed genetic stability of the cag PAL In the second paper we determined the nucleotide sequence of the cag PAI in four clinical isolates, two strains isolated from patients with duodenal ulcer, and two from patients with gastric cancer. These strains all harbored a functional TFSS and the overall genetic structure of this 40 kb region was similar, with some interesting exceptions. One completely new hypothetical gene, named HP0521B, was found in three of these strains. This gene was present in about half of the Swedish clinical isolates in our study. In addition, in one duodenal ulcer strain a large insertion or rearrangement in the intergenic region between HP0546 and HP0547 was found. This genomic change did not seem to affect the function of the TFSS. The genetic composition of the H. pylori population in two individuals was examined in paper three. Subclones isolated from two time points with a nine-year interval were used. When sequencing ten loci (-6,000 bp) in three subclones from each time point, only two substitutions were found in one patient and no differences in the other. Further microarray genotyping revealed distinct differences between the subclones within the patients regardless of time of collection, indicating a potent micro-diversity. In the fourth paper we characterized a putative Nudix hydrolase, NudA, in H. pylori. The preferred substrate of NudA was AP4A, a molecule found at elevated concentrations in cells exposed to oxidative and heat stress. When challenging an isogenic mutant of nudA and a wild type with hydrogen peroxide, the mutant was less capable to survive. NudA was found to be an abundant enzyme in H. pylori, expressed at equal amounts at all stages of growth and during stress exposure. This work has increased our understanding of the complex genetic diversity of H. pylori, and revealed the function of a Nudix hydrolase likely to be important for the persistence of this bacterium in the human stomach.
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| 4. |
- Lundin, Annelie, et al.
(författare)
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The NudA protein in the gastric pathogen Helicobacter pylori is an ubiquitous and constitutively expressed dinucleoside polyphosphate hydrolase
- 2003
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 278:14, s. 12574-12578
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The gastric pathogen Helicobacter pylori harbors one Nudix hydrolase, NudA, that belongs to the nucleoside polyphosphate hydrolase subgroup. In this work, the enzymatic activity of purified recombinant NudA protein was analyzed on a number of nucleoside polyphosphates. This predicted 18.6-kDa protein preferably hydrolyzes diadenosine tetraphosphate, Ap(4)A at a k(cat) of 0.15 s(-1) and a K(m) of 80 microm, resulting in an asymmetrical cleavage of the molecule into ATP and AMP. To study the biological role of this enzyme in H. pylori, an insertion mutant was constructed. There was a 2-7-fold decrease in survival of the mutant as compared with the wild type after hydrogen peroxide exposure but no difference in survival after heat shock or in spontaneous mutation frequency. Western blot analyses revealed that NudA is constitutively expressed in H. pylori at different growth stages and during stress, which would indicate that this protein has a housekeeping function. Given that H. pylori is a diverse species and that all the H. pylori strains tested in this study harbor the nudA gene and show protein expression, we consider NudA to be an important enzyme in this bacterium.
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| 6. |
- Thelaus, Johanna, et al.
(författare)
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Network Experiences from a Cross-Sector Biosafety Level-3 Laboratory Collaboration : A Swedish Forum for Biopreparedness Diagnostics
- 2017
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Ingår i: Health Security. - : Mary Ann Liebert. - 2326-5094 .- 2326-5108. ; 15:4, s. 384-391
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Tidskriftsartikel (refereegranskat)abstract
- The Swedish Forum for Biopreparedness Diagnostics (FBD) is a network that fosters collaboration among the 4 agencies with responsibility for the laboratory diagnostics of high-consequence pathogens, covering animal health and feed safety, food safety, public health and biodefense, and security. The aim of the network is to strengthen capabilities and capacities for diagnostics at the national biosafety level-3 (BSL-3) laboratories to improve Sweden's biopreparedness, in line with recommendations from the EU and WHO. Since forming in 2007, the FBD network has contributed to the harmonization of diagnostic methods, equipment, quality assurance protocols, and biosafety practices among the national BSL-3 laboratories. Lessons learned from the network include: (1) conducting joint projects with activities such as method development and validation, ring trials, exercises, and audits has helped to build trust and improve communication among participating agencies; (2) rotating the presidency of the network steering committee has fostered trust and commitment from all agencies involved; and (3) planning for the implementation of project outcomes is important to maintain gained competencies in the agencies over time. Contacts have now been established with national agencies of the other Nordic countries, with an aim to expanding the collaboration, broadening the network, finding synergies in new areas, strengthening the ability to share resources, and consolidating long-term financing in the context of harmonized European biopreparedness.
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