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Comstedt, Pär
Publications (10 of 10) Show all publications
Hernandez, J., Bonnedahl, J., Eliasson, I., Wallensten, A., Comstedt, P., Johansson, A., . . . Drobni, M. (2010). Globally disseminated human pathogenic Escherichia coli of O25b-ST131 clone, harbouring bla(CTX-M-15), found in Glaucous-winged gull at remote Commander Islands, Russia. Environmental Microbiology Reports, 2(2), 329-332
Open this publication in new window or tab >>Globally disseminated human pathogenic Escherichia coli of O25b-ST131 clone, harbouring bla(CTX-M-15), found in Glaucous-winged gull at remote Commander Islands, Russia
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2010 (English)In: Environmental Microbiology Reports, ISSN 1758-2229, E-ISSN 1758-2229, Vol. 2, no 2, p. 329-332Article in journal (Refereed) Published
Abstract [en]

With focus on environmental dissemination of antibiotic resistance among clinically relevant bacteria, such as the rising ESBL type of resistance among Escherichia coli, we investigated antibiotic resistance levels in wild birds in the Commander Islands and Kamchatka, Russia. Despite overall low resistance levels in randomly selected E. coli (one from each sample), we found multi-resistant ESBL-producing E. coli harbouring bla(CTX-M-14) and bla(CTX-M-15) using selective screening. Among these multi-resistant ESBL-producing E. coli we found one bla(CTX-M-15) harbouring strain belonging to the O25b-ST131 clone, recognized for its clonal disseminated worldwide as a human pathogen. The potential in acquiring resistant bacteria of human origin, especially highly pathogenic clones, as well as downstream consequences of that, should not be underestimated but further investigated.

Keywords
Escherichia coli, Drug Resistance
National Category
Microbiology in the medical area
Identifiers
urn:nbn:se:umu:diva-109713 (URN)10.1111/j.1758-2229.2010.00142.x (DOI)000279432000014 ()23766085 (PubMedID)
Available from: 2015-10-05 Created: 2015-10-05 Last updated: 2018-06-07Bibliographically approved
Comstedt, P., Asokliene, L., Eliasson, I., Olsen, B., Wallensten, A., Bunikis, J. & Bergström, S. (2009). Complex population structure of Lyme borreliosis group spirochete Borrelia garinii in subarctic Eurasia.. PloS one, 4(6), e5841
Open this publication in new window or tab >>Complex population structure of Lyme borreliosis group spirochete Borrelia garinii in subarctic Eurasia.
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2009 (English)In: PloS one, ISSN 1932-6203, Vol. 4, no 6, p. e5841-Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:umu:diva-32841 (URN)10.1371/journal.pone.0005841 (DOI)19513109 (PubMedID)
Available from: 2010-03-29 Created: 2010-03-29 Last updated: 2018-06-08Bibliographically approved
Jaenson, T. G., Eisen, L., Comstedt, P., Mejlon, H. A., Lindgren, E., Bergström, S. & Olsen, B. (2009). Risk indicators for the tick Ixodes ricinus and Borrelia burgdorferi sensu lato in Sweden.. Medical and Veterinary Entomology, 23(3), 226-37
Open this publication in new window or tab >>Risk indicators for the tick Ixodes ricinus and Borrelia burgdorferi sensu lato in Sweden.
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2009 (English)In: Medical and Veterinary Entomology, ISSN 0269-283X, E-ISSN 1365-2915, Vol. 23, no 3, p. 226-37Article in journal (Refereed) Published
Abstract [en]

The distributional area of the tick Ixodes ricinus (L.), the primary European vector to humans of Lyme borreliosis spirochaetes (Borrelia burgdorferi sensu lato) and tick-borne encephalitis virus, appears to be increasing in Sweden. It is therefore important to determine which environmental factors are most useful to assess risk of human exposure to this tick and its associated pathogens. The geographical distribution of I. ricinus in Sweden was analysed with respect to vegetation zones and climate. The northern limit of I. ricinus and B. burgdorferi s.l. in Sweden corresponds roughly to the northern limit of the southern boreal vegetation zone, and is characterized climatically by snow cover for a mean duration of 150 days and a vegetation period averaging 170 days. The zoogeographical distribution of I. ricinus in Sweden can be classified as southerly-central, with the centre of the distribution south of the Limes Norrlandicus. Ixodes ricinus nymphs from 13 localities in different parts of Sweden were examined for the presence of B. burgdorferi s.l. and found to be infected with Borrelia afzelii and Borrelia garinii. Tick sampling localities were characterized on the basis of the density of Borrelia-infected I. ricinus nymphs, presence of specific mammals, dominant vegetation and climate. Densities of I. ricinus nymphs and Borrelia-infected nymphs were significantly correlated, and nymphal density can thus serve as a general indicator of risk for exposure to Lyme borreliosis spirochaetes. Analysis of data from this and other studies suggests that high densities of Borrelia-infected nymphs typically occur in coastal, broadleaf vegetation and in mixed deciduous/spruce vegetation in southern Sweden. Ixodes ricinus populations consistently infected with B. burgdorferi s.l. can occur in: (a) biotopes with shrews, rodents, hares and birds; (b) biotopes with shrews, rodents, hares, deer and birds, and (c) island locations where the varying hare (Lepus timidus) is the only mammalian tick host.

Identifiers
urn:nbn:se:umu:diva-46285 (URN)10.1111/j.1365-2915.2009.00813.x (DOI)19712153 (PubMedID)
Available from: 2011-08-30 Created: 2011-08-30 Last updated: 2018-06-08
Comstedt, P. (2008). Biology of Borrelia garinii Spirochetes. (Doctoral dissertation). Umeå: Molekylärbiologi (Medicinska fakulteten)
Open this publication in new window or tab >>Biology of Borrelia garinii Spirochetes
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Lyme borreliosis is a tick-transmitted infectious disease. The causative agents are spiral-shaped bacteria and the most common sign of infection is a skin rash at the site of the tick bite. If not treated with antibiotics, the bacteria can disseminate and cause a variety of different manifestations including arthritis, carditis or neurological problems. The disease is a zoonosis and the bacteria are maintained in nature by different vertebrate reservoir host animals. In Europe, three different Borrelia genospecies cause Lyme borreliosis: B. burgdorferi, B. afzelii and B. garinii. The latter depends in part on birds as its reservoir host. B. garinii bacteria have been found in a marine enzootic infection cycle worldwide and also among terrestrial birds. This thesis suggests that passerine birds and seabirds constitute an important reservoir for B. garinii bacteria also with clinical importance. We have found bacteria very similar to Lyme borreliosis causing isolates in ticks infesting migrating passerine birds. The birds not only transport infected ticks, but are competent reservoir hosts, as measured by their ability to infect naïve ticks. Their role as a reservoir host is dependent on their foraging behavior, where ground-dwelling birds are of greater importance than other species. When comparing B. garinii isolates from Europe, the Arctic and North Pacific, and including isolates from seabirds, passerine birds, Ixodes ricinus ticks and Lyme borreliosis patients, we found that phylogenetic grouping was not necessarily dependent on geographical or biological origin. B. garinii from seabirds were very heterogeneous and found in all different groups. Therefore, the marine and the terrestrial infection cycles are likely to overlap. This was supported by the fact that B. garinii isolated from seabirds can establish a long-term infection in mice. Bacteria from the genospecies B. garinii are overrepresented among neuroborreliosis patients. Interestingly, many clinical B. garinii isolates are sensitive to human serum and have shown weak binding to the complement inhibitor protein factor H. By transforming a serum-sensitive B. garinii isolate with a shuttle vector containing the gene for the factor H binding protein OspE from complement-resistant B. burgdorferi, serum resistance could be increased. In addition, neurovirulent B. garinii strains recently isolated from neuroborreliosis patients were shown to express a factor H binding protein, not found in bacteria that had been kept in culture for a long time. This protein may contribute to the virulence of neuroborreliosis-causing B. garinii strains. When testing B. garinii isolates from Lyme borreliosis patients and seabirds for resistance to human serum, all members of the latter group were sensitive to even low levels of serum. This suggests that seabird isolates are not capable of infecting humans. In agreement with this, B. garinii isolated from seabirds do not appear to bind human factor H.

Place, publisher, year, edition, pages
Umeå: Molekylärbiologi (Medicinska fakulteten), 2008. p. 73
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1161
Keywords
Borrelia garinii, Lyme borreliosis, birds, migration, reservoir host, complement, Ixodes ricinus, Europe, Asia, infection cycle
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-1578 (URN)978-91-7264-521-9 (ISBN)
Public defence
2008-03-28, Major Groove, 6L, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2008-03-14 Created: 2008-03-14 Last updated: 2018-06-09Bibliographically approved
Larsson, C., Comstedt, P., Olsen, B. & Bergström, S. (2007). First record of Lyme disease Borrelia in the Arctic. Vector Borne and Zoonotic Diseases, 7(3), 453-456
Open this publication in new window or tab >>First record of Lyme disease Borrelia in the Arctic
2007 (English)In: Vector Borne and Zoonotic Diseases, ISSN 1530-3667, E-ISSN 1557-7759, Vol. 7, no 3, p. 453-456Article in journal (Refereed) Published
Abstract [en]

The epidemiology and ecology of Lyme disease is very complex, and its reported geographical distribution is constantly increasing. Furthermore, the involvement of birds in long distance dispersal and their role as reservoir hosts is now well established. In this study, we have shown that sea birds in the Arctic region of Norway carry Ixodes uriae ticks infected with Lyme disease Borrelia garinii spirochetes. Interestingly, DNA sequencing showed that these isolates are closely related to B. garinii previously isolated from birds, as well as from clinical specimens in northern Europe.

National Category
Microbiology in the medical area Infectious Medicine Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:umu:diva-19556 (URN)10.1089/vbz.2006.0644 (DOI)17767412 (PubMedID)
Available from: 2009-03-06 Created: 2009-03-06 Last updated: 2018-06-09Bibliographically approved
Östberg, Y., Berg, S., Comstedt, P., Wieslander, Å. & Bergström, S. (2007). Functional analysis of a lipid galactosyltransferase synthesizing the major envelope lipid in the Lyme disease spirochete Borrelia burgdorferi. FEMS Microbiology Letters, 272(1), 22-29
Open this publication in new window or tab >>Functional analysis of a lipid galactosyltransferase synthesizing the major envelope lipid in the Lyme disease spirochete Borrelia burgdorferi
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2007 (English)In: FEMS Microbiology Letters, ISSN 0378-1097, E-ISSN 1574-6968, Vol. 272, no 1, p. 22-29Article in journal (Refereed) Published
Abstract [en]

One of the major lipids in the membranes of Borrelia burgdorferi is monogalactosyl diacylglycerol (MGalDAG), a glycolipid recently shown to carry antigenic potency. Herein, it is shown that the gene mgs (TIGR designation bb0454) of B. burgdorferi encodes for the protein bbMGS that, when expressed in Escherichia coli, catalyzes the glycosylation of 1,2-diacylglycerol with specificity for the donor substrate UDP-Gal yielding MGalDAG. Related lipid enzymes were found in many Gram-positive bacteria. The presence of this galactosyltransferase activity and synthesis of a cholesteryl galactoside by another enzyme were verified in B. burgdorferi cell extract. Besides MGalDAG, phosphatidylcholine, phosphatidylglycerol, and cholesterol were also found as major lipids in the cell envelope. The high isoelectric point of bbMGS and clustered basic residues in its amino acid sequence suggest that the enzyme interacts with acidic lipids in the plasma membrane, in agreement with strong enzymatic activation of bbMGS by phosphatidylglycerol. The membrane packing and immunological properties of MGalDAG are likely to be of great importance in vivo.

National Category
Cell and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-48648 (URN)10.1111/j.1574-6968.2007.00728.x (DOI)17456185 (PubMedID)
Available from: 2011-10-26 Created: 2011-10-26 Last updated: 2018-06-08Bibliographically approved
Comstedt, P., Bergström, S., Olsen, B., Garpmo, U., Marjavaara, L., Mejlon, H., . . . Bunikis, J. (2006). Migratory passerine birds as reservoirs of Lyme borreliosis in Europe.. Emerging Infectious Diseases, 12(7), 1087-95
Open this publication in new window or tab >>Migratory passerine birds as reservoirs of Lyme borreliosis in Europe.
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2006 (English)In: Emerging Infectious Diseases, ISSN 1080-6040, Vol. 12, no 7, p. 1087-95Article in journal (Refereed) Published
Abstract [en]

To define the role of birds as reservoirs and disseminators of Borrelia spirochetes, we characterized tick infestation and reservoir competence of migratory passerine birds in Sweden. A total of 1,120 immature Ixodes ricinus ticks were removed from 13,260 birds and assayed by quantitative polymerase chain reaction (PCR) for Borrelia, followed by DNA sequencing for species and genotype identification. Distributions of ticks on birds were aggregated, presumably because of varying encounters with ticks along migratory routes. Lyme borreliosis spirochetes were detected in 160 (1.4%) ticks. Borrelia garinii was the most common species in PCR-positive samples and included genotypes associated with human infections. Infestation prevalence with infected ticks was 5 times greater among ground-foraging birds than other bird species, but the 2 groups were equally competent in transmitting Borrelia. Migratory passerine birds host epidemiologically important vector ticks and Borrelia species and vary in effectiveness as reservoirs on the basis of their feeding behavior.

Keywords
Animals, Bird Diseases/parasitology, Borrelia/classification, Disease Reservoirs, Europe/epidemiology, Lyme Disease/*epidemiology/microbiology, Passeriformes/*microbiology, Tick Infestations/veterinary, Ticks/microbiology
Identifiers
urn:nbn:se:umu:diva-12902 (URN)16836825 (PubMedID)
Available from: 2008-01-08 Created: 2008-01-08 Last updated: 2018-06-09Bibliographically approved
Alitalo, A., Meri, T., Comstedt, P., Jeffery, L., Tornberg, J., Strandin, T., . . . Meri, S. (2005). Expression of complement factor H binding immunoevasion proteins in Borrelia garinii isolated from patients with neuroborreliosis.. Eur J Immunol, 35(10), 3043-3053
Open this publication in new window or tab >>Expression of complement factor H binding immunoevasion proteins in Borrelia garinii isolated from patients with neuroborreliosis.
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2005 (English)In: Eur J Immunol, ISSN 0014-2980, Vol. 35, no 10, p. 3043-3053Article in journal (Refereed) Published
Abstract [en]

The Lyme disease-pathogen Borrelia burgdorferi binds the complement inhibitor factor H (FH) to its outer surface protein E- (OspE) and BbA68-families of lipoproteins. In earlier studies, only serum-resistant strains of the genospecies B. burgdorferi sensu stricto or B. afzelii, but not serum-sensitive B. garinii strains, have been shown to bind FH. Since B. garinii often causes neuroborreliosis in man, we have readdressed the interactions of B. garinii with FH. B. garinii 50/97 strain did not express FH-binding proteins. By transforming the B. garinii 50/97 strain with an OspE-encoding gene from complement-resistant B. burgdorferi (ospE-297), its resistance to serum killing could be increased. OspE genes were detected and cloned from the B. garinii BITS, Pistoia and 40/97 strains by PCR and sequencing. The deduced amino acid sequences differed in an N-terminal lysine-rich FH-binding region from OspE sequences of resistant strains. Recombinant B. garinii BITS OspE protein was found to have a considerably lower FH-binding activity than the B. burgdorferi sensu stricto 297 OspE protein P21 (P21-297). Unlike bacteria that had been kept in culture for a long time, neurovirulent B. garinii strains from neuroborreliosis patients were found to express approximately 27-kDa FH-binding proteins. These were not recognized by polyclonal anti-OspE or anti-BbA68 antibodies. We conclude that B. garinii strains carry ospE genes but have a decreased expression of OspE proteins and a reduced ability to bind FH, especially when grown for prolonged periods in vitro. Recently isolated neuroinvasive B. garinii strains, however, can express FH-binding proteins, which may contribute to the virulence of neuroborreliosis-causing B. garinii strains.

Keywords
Amino Acid Sequence, Animals, Antigens; Bacterial/*genetics/immunology/metabolism, Bacterial Outer Membrane Proteins/*genetics/immunology/metabolism, Bacterial Proteins/*genetics/immunology/metabolism, Base Sequence, Borrelia burgdorferi Group/*pathogenicity/*physiology, Complement Factor H/immunology/metabolism, Humans, Immunoblotting, Lipoproteins/*genetics/immunology/metabolism, Lyme Neuroborreliosis/immunology/*metabolism, Molecular Sequence Data, Polymerase Chain Reaction, Surface Plasmon Resonance
Identifiers
urn:nbn:se:umu:diva-12936 (URN)16208765 (PubMedID)
Available from: 2007-10-03 Created: 2007-10-03 Last updated: 2018-06-09Bibliographically approved
Pinne, M., Östberg, Y., Comstedt, P. & Bergström, S. (2004). Molecular analysis of the channel-forming protein P13 and its paralogue family 48 from different Lyme disease Borrelia species. Microbiology, 150(Pt 3), 549-559
Open this publication in new window or tab >>Molecular analysis of the channel-forming protein P13 and its paralogue family 48 from different Lyme disease Borrelia species
2004 (English)In: Microbiology, ISSN 1350-0872, E-ISSN 1465-2080, Vol. 150, no Pt 3, p. 549-559Article in journal (Refereed) Published
Abstract [en]

The aetiological agent of Lyme disease, Borrelia burgdorferi cycles between its tick vector and mammalian hosts, implying that it can sense different environments and consequently change the expression of genes encoding several surface-associated proteins. The genome of the type strain B. burgdorferi B31 has revealed 175 different gene families. The p13 gene, situated on the chromosome, encodes a channel-forming protein that belongs to the gene family 48 consisting of eight additional paralogous genes. The heterogeneity of the P13 protein from different Lyme disease Borrelia strains was investigated. The predicted surface-exposed domains are the most heterogeneous regions and contain probable epitopes of P13. The membrane-spanning architecture of P13 was determined and a model for the location of this protein in the outer membrane is presented. The transcription of the paralogues of gene family 48 during in vitro culturing and in a mouse infection model was also analysed. The bba01 gene is the only p13 paralogue present in all three Lyme-disease-causing genospecies; it is stable during cultivation in vitro and the BBA01 protein was expressed in all Borrelia strains investigated. Conversely, paralogues bbi31, bbq06 and bbh41 were only detected in B. burgdorferi and the corresponding plasmids harbouring bbi31 and bbh41 were lost during in vitro passage. Finally, p13 and bbi31 are the only members of gene family 48 that are transcribed in mice, suggesting their importance during mammalian infection.

Keywords
Amino Acid Sequence, Animals, Bacterial Outer Membrane Proteins/chemistry/genetics/physiology, Bacterial Proteins/chemistry/*genetics/physiology, Base Sequence, Borrelia/*genetics/pathogenicity/physiology, DNA; Bacterial/genetics, Epitope Mapping, Genes; Bacterial, Humans, Ion Channels/chemistry/genetics/physiology, Lyme Disease/microbiology, Mice, Mice; Inbred C3H, Models; Molecular, Molecular Sequence Data, Multigene Family, Sequence Homology; Amino Acid, Species Specificity
National Category
Cell and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-12966 (URN)10.1099/mic.0.26728-0 (DOI)14993304 (PubMedID)
Available from: 2008-01-10 Created: 2008-01-10 Last updated: 2018-06-09Bibliographically approved
Comstedt, P., Larsson, C., Meri, T., Meri, S. & Bergström, S.Borrelia garinii isolated from seabirds can infect rodents but is sensitive to normal human serum.
Open this publication in new window or tab >>Borrelia garinii isolated from seabirds can infect rodents but is sensitive to normal human serum
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(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:umu:diva-3006 (URN)
Available from: 2008-03-14 Created: 2008-03-14 Last updated: 2018-06-09Bibliographically approved
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