| 1. |
- Guo, Betty P, et al.
(författare)
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Relapsing fever Borrelia binds to neolacto glycans and mediates rosetting of human erythrocytes.
- 2009
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 106:46, s. 19280-5
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Tidskriftsartikel (refereegranskat)abstract
- A hallmark of acute relapsing fever borreliosis is severe bacteremia. Some Borrelia species, such as B. duttonii and B. crocidurae, associate with erythrocytes and induce aggregation recognized as erythrocyte rosetting. Erythrocyte rosettes contribute to disease severity by increased tissue invasiveness (such as invasion of CNS and encephalitis), hemorrhaging, and reduced blood flow in affected microcapillaries. Here we report that relapsing fever Borrelia binds to neolacto (Galbeta4GlcNAcbeta3Galbeta4Glcbeta1)-carrying glycoconjugates that are present on human erythrocytes. This interaction is of low affinity but is compensated for by the multivalency of neo-lacto-oligosaccharides on the erythrocyte cell surface. Hence, the protein-carbohydrate interaction is dependent on multivalent neolacto-glycans to mediate binding.
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| 2. |
- Barcena-Uribarri, Ivan, et al.
(författare)
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Use of Nonelectrolytes Reveals the Channel Size and Oligomeric Constitution of the Borrelia burgdorferi P66 Porin
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 8:11, s. e78272-
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Tidskriftsartikel (refereegranskat)abstract
- In the Lyme disease spirochete Borrelia burgdorferi, the outer membrane protein P66 is capable of pore formation with an atypical high single-channel conductance of 11 nS in 1 M KCl, which suggested that it could have a larger diameter than 'normal' Gram-negative bacterial porins. We studied the diameter of the P66 channel by analyzing its single-channel conductance in black lipid bilayers in the presence of different nonelectrolytes with known hydrodynamic radii. We calculated the filling of the channel with these nonelectrolytes and the results suggested that nonelectrolytes (NEs) with hydrodynamic radii of 0.34 nm or smaller pass through the pore, whereas neutral molecules with greater radii only partially filled the channel or were not able to enter it at all. The diameter of the entrance of the P66 channel was determined to be <= 1.9 nm and the channel has a central constriction of about 0.8 nm. The size of the channel appeared to be symmetrical as judged from one-sidedness of addition of NEs. Furthermore, the P66-induced membrane conductance could be blocked by 80-90% by the addition of the nonelectrolytes PEG 400, PEG 600 and maltohexaose to the aqueous phase in the low millimolar range. The analysis of the power density spectra of ion current through P66 after blockage with these NEs revealed no chemical reaction responsible for channel block. Interestingly, the blockage of the single-channel conductance of P66 by these NEs occurred in about eight subconductance states, indicating that the P66 channel could be an oligomer of about eight individual channels. The organization of P66 as a possible octamer was confirmed by Blue Native PAGE and immunoblot analysis, which both demonstrated that P66 forms a complex with a mass of approximately 460 kDa. Two dimension SDS PAGE revealed that P66 is the only polypeptide in the complex.
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| 3. |
- Bárcena-Uribarri, Iván, et al.
(författare)
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Use of nonelectrolytes reveals the channel size and oligomeric constitution of the Borrelia burgdorferi P66 porin
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The outer membrane protein P66 of the Lyme disease spirochete Borrelia burgdorferi is capable of pore formation with an atypical high single-channel conductance of 11 nS in 1 M KCl. We studied in a non-theoretical manner the diameter of the P66 channel by analyzing its single-channel conductance in black lipid bilayers in the presence of different nonelectrolytes with known hydrodynamic radii. Furthermore, we calculated the filling of the channel with these nonelectrolytes and the results revealed that nonelectrolytes with hydrodynamic radii of 0.34 nm or smaller pass through the pore, whereas neutral molecules with greater radii only partially filled the channel or were not able to enter it at all. Thus, the diameter of the P66 entrance was determined to be ≤ 1.9 nm with a constriction site diameter of about 0.7 nm. Furthermore, the P66-induced membrane conductance could be blocked by 80-90% after addition of the nonelectrolytes PEG 400, PEG 600 and maltohexaose in the low millimolar range. Interestingly, the analysis of the power density spectra of P66 after blockage with nonelectrolytes revealed no chemical interaction responsible for channel block. The blockage of one P66 single-channel conductance unit of 11 nS occurred by seven subconducting states, thus indicating a heptameric organization of the P66 oligomer. This organization of P66 as a heptamer was confirmed by Blue Native PAGE and immunoblot analysis, which demonstrated that P66 forms a complex with a mass of approximately 460 kDa.
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| 4. |
- Bergström, Sven, 1950-
(författare)
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Chromosomal β-lactamases in enterobacteria and in vivo evolution of β-lactam resistance
- 1983
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The ß-lactam antibiotics are the most important antibacterial agents in the treatment of infectious diseases. A severe problem in ß-lactam therapy is the emergence of ß-lactam resistant bacteria. Clinical ß-lactam resistance is most often due to the production of ß-lactamases. ß-lactamase genes reside either on plasmids or on the chromosome. The aim of this study was to acquire an understanding of organisation and regulation of chromosomal ß- lactamase genes in different Gram negative species and to elucidate the mechanisms for ampC hyperproduction in the in vivo situation.By DNA hybridization with an ampC probe from Escherichia coli K-12 it was shown that other Gram negative bacteria contained an artpC like chromosomal gene, suggesting a common evolutionary origin. Furthermore, the preceding frd operon that overlaps the ampC gene in E. coli K-12 was found to be much more conserved than the ampC gene in the bacterial species investigated.The ampC and frd opérons in Shigella sonnei and Citrobacter freundii were cloned and characterized by physical mapping. The respective maps were compared to the ampC and frd region in E. coli K-12. The physical map of Sh. sonnei was almost identical to the E. coli K-12 map, whereas in C. freundii only the frd region exhibited any considerable homology. Moreover, in C. freundii, the anpC and frd regions were separated by 1100 basepairs. It is suggested that this DNA is involved in the induction of ß-lactamase production in this organism. A hypothesis for the evolution of the anpC operon in enterobacteria is presented.By isolating and characterizing six ß-lactam resistant clinica], isolates of E. coli hyperproducing the dhrcmosomal ß-lactamase, genetic mechanisms for in vivo evolved resistance was aimed at. These isolates exhibited a 24-48 fold increase in ß-lactamase production. The ß-lactamase produced was found to be biochemically and immunologically identical to the ß-lactamase produced by E. coli K-12. The ampC control region of these six E. coli isolates was DNA-seqenced. The cause of ß-lactamase hyperproduction in five of the clinical E. coli isolates, identical in the DNA segment sequenced, was due to a strong novel ampC promoter displaced 5 bp upstream of the ampC promoter defined in E. coli K-12. The ß-lactamase hyperproduction in the sixth clinical isolate was shown to be caused by two mutations affecting both the promoter and the attenuator in the regulatory region defined by E. coli K- 12. The obtained changes were sufficient to explain the increase in ampC ß- 1 act ama se expression exhibited in these clinical E. coli isolates.Sequence analysis of the ampC control region in Sh. sonnei revealed that it was, with one exception, identical to the one found in the five clinical E. coli ß-lactamase hyperproducers. The only difference was in a position that creates the strong novel ampC promoter in the E. coli hyperproducers. By isolating spontaneous Sh. sonnei mutants with a 40-fold increase in ß-lactamase production carrying the same novel ampC promoter as the clinical E. coli isolates it was concluded that this DNA segment has been transferred in vivo frcm Shigella to E. coli across the species barrier.
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| 5. |
- Comstedt, Pär, 1977-, et al.
(författare)
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Complex population structure of Lyme borreliosis group spirochete Borrelia garinii in subarctic Eurasia.
- 2009
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 4:6, s. e5841-
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Tidskriftsartikel (refereegranskat)abstract
- Borrelia garinii, a causative agent of Lyme borreliosis in Europe and Asia, is naturally maintained in marine and terrestrial enzootic cycles, which primarily involve birds, including seabirds and migratory passerines. These bird groups associate with, correspondingly, Ixodes uriae and Ixodes ricinus ticks, of which the latter species may bite and transmit the infection to humans. Studies of the overlap between these two natural cycles of B. garinii have been limited, in part due to the absence of representative collections of this spirochete's samples, as well as of the lack of reliable measure of the genetic heterogeneity of its strains. As a prerequisite for understanding the epidemiological correlates of the complex maintenance of B. garinii, the present study sought to assess the diversity and phylogenetic relationships of this species' strains from its natural hosts and patients with Lyme borreliosis from subarctic Eurasia. We used sequence typing of the partial rrs-rrl intergenic spacer (IGS) of archived and prospective samples of B. garinii from I. uriae ticks collected predominantly on Commander Islands in North Pacific, as well as on the islands in northern Sweden and arctic Norway. We also typed B. garinii samples from patients with Lyme borreliosis and I. ricinus ticks infesting migratory birds in southern Sweden, or found questing in selected sites on the islands in the Baltic Sea and Lithuania. Fifty-two (68%) of 77 B. garinii samples representing wide geographical range and associated with I. ricinus and infection of humans contributed 12 (60%) of total 20 identified IGS variants. In contrast, the remaining 25 (32%) samples recovered from I. uriae ticks from a few islands accounted for as many as 10 (50%) IGS types, suggesting greater local diversity of B. garinii maintained by seabirds and their ticks. Two IGS variants of the spirochete in common for both tick species were found in I. ricinus larvae from migratory birds, an indication that B. garinii strains are exchanged between different ecological niches. Notably, B. garinii variants associated with I. uriae ticks were found in each of the six clusters, representing two phylogenetic lineages of this species identified among the studied samples. Our findings suggest that B. garinii in subarctic Eurasia comprises two partially overlapping populations with different levels of genetic heterogeneity, presumably, due to distinctive selective pressures on the spirochete in its marine and terrestrial enzootic cycles.
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| 6. |
- Larsson, Christer, 1975-, et al.
(författare)
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A novel animal model of Borrelia recurrentis louse-borne relapsing fever borreliosis using immunodeficient mice
- 2009
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Ingår i: PLoS Neglected Tropical Diseases. - : PLoS, Public Library of Science. - 1935-2727 .- 1935-2735. ; 3:9, s. e522-
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Tidskriftsartikel (refereegranskat)abstract
- Louse-borne relapsing fever (LBRF) borreliosis is caused by Borrelia recurrentis, and it is a deadly although treatable disease that is endemic in the Horn of Africa but has epidemic potential. Research on LBRF has been severely hampered because successful infection with B. recurrentis has been achieved only in primates (i.e., not in other laboratory or domestic animals). Here, we present the first non-primate animal model of LBRF, using SCID (-B, -T cells) and SCID BEIGE (-B, -T, -NK cells) immunocompromised mice. These animals were infected with B. recurrentis A11 or A17, or with B. duttonii 1120K3 as controls. B. recurrentis caused a relatively mild but persistent infection in SCID and SCID BEIGE mice, but did not proliferate in NUDE (-T) and BALB/c (wild-type) mice. B. duttonii was infectious but not lethal in all animals. These findings demonstrate that the immune response can limit relapsing fever even in the absence of humoral defense mechanisms. To study the significance of phagocytic cells in this context, we induced systemic depletion of such cells in the experimental mice by injecting them with clodronate liposomes, which resulted in uncontrolled B. duttonii growth and a one-hundred-fold increase in B. recurrentis titers in blood. This observation highlights the role of macrophages and other phagocytes in controlling relapsing fever infection. B. recurrentis evolved from B. duttonii to become a primate-specific pathogen that has lost the ability to infect immunocompetent rodents, probably through genetic degeneration. Here, we describe a novel animal model of B. recurrentis based on B- and T-cell-deficient mice, which we believe will be very valuable in future research on LBRF. Our study also reveals the importance of B-cells and phagocytes in controlling relapsing fever infection.
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| 7. |
- Lundqvist, Jenny, 1975-, et al.
(författare)
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Concomitant Infection Decreases the Malaria Burden but Escalates Relapsing Fever Borreliosis
- 2010
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Ingår i: Infection and Immunity. - : American Society for Microbiology. - 0019-9567 .- 1098-5522. ; 78:5, s. 1924-1930
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Tidskriftsartikel (refereegranskat)abstract
- About 500 million cases of malaria occur annually. However, a substantial number of patients who actually have relapsing fever (RF) Borrelia can be misdiagnosed with malaria due to similar manifestations and geographic distribution of the two diseases. More alarmingly, high prevalence of concomitant infections with malaria and RF Borrelia has been reported. Therefore, we used a mouse model to study the effects of such mixed infection. We observed a 21-fold increase in spirochete titers, whereas the numbers of parasitized erythrocytes were reduced 15-fold. This may be explained by polarization of the host immune response towards the intracellular malaria parasite, resulting in unaffected extracellular spirochetes and hosts that succumb to sepsis. Mixed infection also resulted in severe malaria anemia with low hemoglobin levels, even though the parasite counts were low. Overall, co-infected animals had higher fatality rate and shorter time to death than both malaria and RF single infection. Furthermore, secondary malaria infection reactivated a quiescent RF brain infection, which is the first evidence of a clinically and biologically relevant cue for reactivation of RF Borrelia infection. Our study highlights the importance of investigating concomitant infections in vivo to elucidate the immune responses that are involved in the clinical outcome.
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| 8. |
- Palmgren, Helena, 1955-, et al.
(författare)
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Enteropathogenic Bacteria in Migrating Birds Arriving in Sweden
- 1997
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Ingår i: Scandinavian Journal of Infectious Diseases. - : Scandinavian University Press. - 0036-5548 .- 1651-1980. ; 29:6, s. 565-568
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Tidskriftsartikel (refereegranskat)abstract
- Birds have been thought to play a role in transmitting infectious agents like influenza, Borrelia and Salmonella. To investigate the role of migrating birds in the dispersal of enteropathogenic bacteria, stool samples from 151 wild birds (50 gulls and 101 passerines) just entering Sweden from their winter grounds were analysed for Salmonella spp., Campylobacter spp. and EHEC O157:H7. The thermophilic isolated enteropathogens found were further analysed by antibiograms. Among the 50 gulls examined, we found 2 isolates of Salmonella typhimurium with multiple antibiotic resistance. Three isolates of C. jejuni were found in the 101 stool samples from passerines. We did not isolate EHEC O157:H7 in any of the bird stools examined.
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| 9. |
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| 10. |
- Palmgren, Helena, 1955-, et al.
(författare)
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Salmonella in sub-Antarctica : low heterogeneity in salmonella serotypes in South Georgian seals and birds
- 2000
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Ingår i: Epidemiology and Infection. - : Cambridge University Press. - 0950-2688 .- 1469-4409. ; 125:2, s. 257-262
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Tidskriftsartikel (refereegranskat)abstract
- The number of human visitors to Antarctica is increasing rapidly, and with it a risk of introducing infectious organisms to native animals. To study the occurrence of salmonella serotypes in sub- Antarctic wildlife, faecal samples were collected from gentoo penguins, macaroni penguins, gray-headed albatrosses, black-browed albatrosses and Antarctic fur seals on Bird Island in the South Georgian archipelago during the austral summer of 1996 and 1998. In 1996, S. havana, S. typhimurium and S. enteritidis were isolated from 7% of gentoo penguins and 4% of fur seals. In 1998, however, 22% of fur seals were found to be infected with S. havana, S. enteritidis and S. newport. All isolates, except one, showed identical pulsed-field gel electrophoresis-patterns within each serotype, irrespective of sampling year and animal reservoir. No significant antibiotic resistance was found. The very low heterogeneity in the salmonella isolates found could either indicate a high genetic adaptation of the bacteria to the environment or a recent introduction of salmonella into the area.
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| 11. |
- Sellstedt, Magnus, 1981-, et al.
(författare)
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Synthesis and Characterization of a Multi Ring-Fused 2-Pyridone-Based Fluorescent Scaffold
- 2010
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :32, s. 6171-6178
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Tidskriftsartikel (refereegranskat)abstract
- A series of compounds based on a novel fluorescent scaffold have been synthesized. Most of the compounds displayed high quantum yields of fluorescence and unusually long fluorescence lifetimes. HeLa cells were treated with one of the compounds and its use as a fluorescent dye was demonstrated with fluorescence confocal microscopy.
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| 12. |
- Thein, Marcus, et al.
(författare)
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Oms38 is the first identified pore-forming protein in the outer membrane of relapsing fever spirochetes
- 2008
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Ingår i: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 190:21, s. 7035-7042
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Tidskriftsartikel (refereegranskat)abstract
- Relapsing fever is a worldwide, endemic disease caused by several spirochetal species belonging to the genus Borrelia. During the recurring fever peaks, borreliae proliferate remarkably quickly compared to the slow dissemination of Lyme disease Borrelia and therefore require efficient nutrient uptake from the blood of their hosts. This study describes the identification and characterization of the first relapsing fever porin, which is present in the outer membranes of B. duttonii, B. hermsii, B. recurrentis, and B. turicatae. The pore-forming protein was purified by hydroxyapatite chromatography and designated Oms38, for outer membrane-spanning protein of 38 kDa. Biophysical characterization of Oms38 was done by using the black lipid bilayer method, demonstrating that Oms38 forms small, water-filled channels of 80 pS in 1 M KCl that did not exhibit voltage-dependent closure. The Oms38 channel is slightly selective for anions and shows a ratio of permeability for cations over anions of 0.41 in KCl. Analysis of the deduced amino acid sequences demonstrated that Oms38 contains an N-terminal signal sequence which is processed under in vivo conditions. Oms38 is highly conserved within the four studied relapsing fever species, sharing an overall amino acid identity of 58% and with a strong indication for the presence of amphipathic beta-sheets.
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