| 1. |
- Labbé Sandelin, Lisa, 1977-
(author)
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Neoehrlichia mikurensis in Sweden : An emerging tick-borne human pathogen
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Neoehrlichia mikurensis is an emerging tick-borne human pathogen, causing neoehrlichiosis in immunosuppressed and immunocompetent individuals. It targets the vascular endothelium, leading to thromboembolic and vascular events, but can also pass without symptoms. As symptoms easily are misinterpreted, immunosuppressive treatment or chemotherapy is often incorrectly initiated. Diagnostic delay can be considerable.The overall aim of this thesis was to gain a better understanding on N. mikurensis in Sweden, focusing on human infections and public health aspects. The prevalence of N. mikurensis in different populations was examined. The symptomatology of neoehrlichiosis and the risk of transfusion-mediated transmission was studied. N. mikurensis was observed in low prevalences in ticks collected from migratory birds, in tick-bitten individuals, in patients with persistent symptoms attributed to presumed tick-bite exposure, and in blood donors. Fourteen N. mikurensis-positive individuals were identified. The majority were immunocompetent and asymptomatic. Both spontaneous clearance and persistence was observed. Two of 102 tick-bitten individuals were N. mikurensis-positive. Both presented with erythema migrans, but borreliosis was a more probable cause in both. The findings do not support a change in practice regarding first-line treatment of erythema migrans, but further studies are warranted.Persistence of N. mikurensis in blood raises questions regarding the possibility of transmission by transfusion and the risk of activating the infection if immune status is altered. N. mikurensis was identified in seven out of 1 006 blood donors. Look-back and tracing identified 12 recipients who were transfused with blood components from N. mikurensis-positive donors. Several recipients had multiple risk factors for severe neoehrlichiosis, but transfusion-transmitted neoehrlichiosis was not detected. Nevertheless, the possibility that N. mikurensis can be transmitted by transfusion cannot be excluded.Isolates from birds and blood donors were identical to previously reported Swedish human isolates. Migrating birds can act as dispersal vectors of N. mikurensis, but their role as transmission hosts is still unclear.The disease burden and public health impact of neoehrlichiosis is probably small, but information is lacking in several areas. Suspicion of neoehrlichiosis is warranted in immunocompromised and/or splenectomised patients with persistent fever, with or without thromboembolic and vascular events. Furthermore, neoehrlichiosis should be included in the differential diagnosis of anaplasmosis. Besides raised awareness, a possible mandatory notification is proposed as well as a comprehensive surveillance system for transfusion-transmitted infections. One of the priority issues is the possible need for screening of patients living in N. mikurensis-endemic areas before and during immunosuppressive treatment.
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| 2. |
- Christerson, Linus, 1985-
(author)
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High Resolution Genotyping of Chlamydia trachomatis
- 2011
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Doctoral thesis (other academic/artistic)abstract
- Chlamydia trachomatis is an obligate intracellular bacterium of major human health concern, causing urogential chlamydia infections, lymphogranuloma venereum (LGV) and trachoma. Chlamydia is one of the most common sexually transmitted infections worldwide and can cause infertility. In the first four papers described herein we used a high resolution multilocus sequence typing (MLST) system to investigate the epidemiology of C. trachomatis, and showed that MLST is superior to conventional ompA genotyping with respect to resolution. In the fifth paper we simplified the methodology by developing and validating a multilocus typing (MLT) DNA microarray based on the MLST system. In more detail, MLST analysis of consecutive specimens from 2006 in Örebro County in Sweden, and comparison to specimens from 1999-2000, showed that the new variant C. trachomatis (nvCT) is monoclonal and likely has appeared in recent years. MLST analysis of LGV specimens from men who have sex with men (MSM) showed that the increase of LGV in Europe in the last decade indeed was a clonal outbreak, contrary to the USA where LGV might have been present all along. In the third paper, clinical symptoms could not be correlated with the MLST genotypes, suggesting, together with the combined results of all previous studies, that bacterial factors, if important, need to be understood in the context of host factors. MLST analysis of specimens from a high incidence C. trachomatis area in North Norway revealed interesting epidemiological details concerning unusual genetic variants, the nvCT and MSM, but found no significant difference in genetic diversity compared to two other geographic areas in Norway. Lastly, we developed a MLT array that provides high resolution while being rapid and cost-effective, which makes it an interesting alternative for C. trachomatis genotyping. In conclusion, the MLST system and the MLT array have proven to be useful tools and should now be applied in further investigations to improve our understanding of C. trachomatis epidemiology.
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| 3. |
- Eriksson, Per
(author)
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Avian Influenza Virus : Deciphering receptor interactions and their role in interspecies transmission
- 2019
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Doctoral thesis (other academic/artistic)abstract
- Influenza A virus (IAV) annually infects approximately 5–15 % of the human population, causing ~500,000 deaths globally. Novel IAVs have emerged and spread pandemically in the human population, but have over time established endemic circulation with reduced pathogenicity causing seasonal influenza. The natural reservoir of IAVs is wild waterfowl. The past pandemics have been associated with host switch and have partly or entirely originated from birds, or adapted via passage through pigs (postulated IAV mixing vessel). Understanding IAV interspecies transmission mechanisms is essential for pandemic preparedness. Enzootic circulation of avian IAV (AIV) is concentrated to a few waterfowl species, while other bird species seldom are infected. A species barrier preventing IAV interspecies transmission has been suggested. To investigate IAV host range and mixing vessels, histochemistry studies were conducted with tissues from avian species, pigs, and humans. Virus adaptation to new hosts was studied by challenging tufted ducks and chickens with mallard-derived AIVs, together with AIV receptor tropism and glycoproteomic analysis of receptor distribution. Finally, receptor and tissue tropism in ducks was studied systematically for AIV (H1–16). More abundant AIV attachment to human than pig tissues was observed, questioning the pig mixing vessel theory. Attachment patterns of AIVs to bird tissues was generally broad with abundant attachment to trachea. However, among ducks, pronounced attachment was observed to colon of Anas spp., suggesting that intestinal infection might be restricted to Anas spp., whereas other species may be susceptible to respiratory infection. Tufted ducks and chickens could not be infected by intraesophageal inoculation further supporting this hypothesis. Glycan array analysis revealed 3’SLN, 3’STF, and their fucosylated and sulfated analogues as main AIV receptors. Moreover, AIV Neu5Acα2,6 recognition was widespread. Avian respiratory and intestinal tracts glycoproteomic analysis revealed that avian and mammalian receptor structures are much more similar than earlier thought. Furthermore, observed AIV subtype titer variation in challenged tufted ducks and chickens did not correlate with virus receptor tropism. In summary, this thesis suggests that IAV receptor recognition, in particular α2,3 vs. α2,6 sialylated receptor structures, is less important for the IAV interspecies barrier than previously thought.
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| 4. |
- Thegerström, Johanna, 1972-
(author)
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Mycobacterium avium infections in children
- 2009
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Doctoral thesis (other academic/artistic)abstract
- Mycobacterium avium belongs to a group of over 130 species of non-tuberculous mycobacteria (NTM) or environmental mycobacteria. The subspecies Mycobacterium avium avium was originally described as the causative agent of bird tuberculosis, but was later found to cause disease also in humans. Small children display a special form of infection that is seldom detected in other age groups. It manifests as a chronic lymphadenitis usually in the head and neck region. The incidence rate is approximately 1-5/100,000 children/year. However, exposure to this bacterium is high as judged by sensitin skin test studies. Even if a lot of persons are infected with M. avium, a majority of them do not develop disease and the bacterium is therefore considered to be of low virulence, causing disease mainly in immunocompromised persons. Children with M. avium lymphadenitis, however, usually do not have any known deficiencies in the immune system.This thesis elucidates why small children are prone to develop disease by M. avium. Investigation of a possible zoonotic spread of this bacterium to children involved analysis and comparison of different strains isolated from birds and other animals and from children, using the restriction fragment length polymorphism (RFLP) method on insertion sequence IS1245, resulting in the finding that the children were infected exclusively with the new proposed subspecies M. avium hominissuis. Animals in general and birds in particular were infected with the subspecies M. avium avium (using the more narrow definition). Moreover, when investigating the immunological response of human peripheral blood mononuclear cells (PBMCs) to stimulation with M. avium hominissuis and M. avium avium, respectively, it was found that the former subspecies induced lower IFN-γ and IL-17 than the latter, but higher levels of Il-10, which might contribute to explain the higher pathogenicity of M. avium hominissuis in humans.Through studies of the geographical distribution of cases of M. avium infection in children in Sweden and the seasonal variation of the disease, a fluctuation of the incidence over the year was detected, with higher numbers of cases in the autumn months and lower numbers in the late spring. There was a higher incidence rate in children living close to water than in those living in the inland or in the urban areas. Therefore, outdoor natural water is the most probable source of infection in children with M. avium lymphadenitis. Through a descriptive clinical retrospective study, complete surgical removal of the affected lymph node was found to lead to better results than treatment by incision and drainage of abscess or expectation only.Finally there might be several explanations as to why an individual develops disease after infection with M. avium, such as, exposure, bacterial virulence factors or possible specific deficiencies of the immune system of the host or a combination of these factors. Which are the more important factors regarding children with M. avium lymphadenitis is still an open question.
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| 5. |
- Devi, Priya
(author)
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Molecular characterization of the hepatitis C virus core protein
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Hepatitis C virus (HCV) is an RNA virus that causes chronic infection, which can lead to hepatocellular carcinomas in humans. Besides liver diseases, the chronic HCV infection causes a broad spectrum of extrahepatic complications such as lymphoproliferative, metabolic and autoimmune disorders. Notably, HCV encoded core (C) protein is the major virion component that is involved in the oncogenesis and immune subversion. Therefore, detailed molecular characterization of the C protein provides a rational starting point for identification of novel countermeasures against pathogenic HCV infections. In this thesis we have investigated the suppressive effect of the C protein on T cell functions in immortalized cell lines and clinical samples.In paper I, we found that the expression of the C protein enhanced overall tyrosine phosphorylation in immortalized T cells. Interestingly, stable expression of the C protein specifically reduced accumulation of the tyrosine phosphatase SHP-1 mRNA. Our detailed bisulfite sequencing (BS) studies revealed that the SHP-1 P2 promoter was particularly hypermethylated at CpG1 and proximal islands in these cells. In paper II, we presented a new high-throughput next generation bisulfite sequencing (NGS-BS) protocol for the analysis of locus specific CpG methylation in HCV-infected cells using SHP-1 P2 as a model promoter. In line with our data from the BS, the NGS-BS method showed similar methylation profile at CpG1 island in immortalized cells. Strikingly, peripheral blood mononuclear cells (PBMCs) isolated from healthy controls and HCV-positive (HCV+) patients, showed much lower levels of methylation at the CpG1 island with no significant difference in DNA methylation pattern. In paper III, we investigated the mechanism of the C protein-mediated release of Ca2+ from intracellular stores. We identified two distinct regions in the N- and C-terminal parts of the protein that were essential for activation of the Ca2+/NFAT pathway. Of these, the N-terminal region was required for self-association of the C protein into nucleocapsid-like structures whereas the C-terminal part is essential for anchoring the protein to the ER-membrane. In paper IV, we presented a PCR based diagnostic method for the specific detection of positive and negative strand HCV RNA using primers with a non-viral tag. The method was evaluated by analysing the plasma and PBMC samples from chronic HCV+ patients.Taken together, our studies provide more detailed molecular characterization of the HCV C protein functions in immortalized as well as in HCV+ T cells. Importantly, specific DNA methylation pattern of the SHP-1 gene promoter may function as a potential prognostic marker for the disease progression in HCV-induced tumors. In addition, our updated PCR-based HCV diagnostic method may provide a more specific tool to monitor HCV infections in minor reservoirs.
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| 6. |
- Hoffman, Tove
(author)
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Dispersal of ticks and their microorganisms by African-Western Palaearctic migratory birds
- 2021
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Doctoral thesis (other academic/artistic)abstract
- In Europe, tick-borne diseases are the most widespread and common vector-borne diseases and their geographical distribution is increasing. The dispersal of ticks depends on the movements of their vertebrate hosts. Avian hosts are more likely to be involved in long-distance range expansion of ticks due to their migration pattern. Billions of birds in the African-Palaearctic migration system migrate biannually between breeding grounds in the Palaearctic and wintering grounds in Africa and thereby create natural links between Africa, Europe, and Asia. In this thesis the dispersal of ticks and their microorganisms by northbound migratory birds utilizing flyways in the African-Western Palaearctic region has been investigated and the association between bird ecology and tick taxon addressed. The results suggest that long-distance migratory birds with wintering regions in Africa are involved in northward dispersal of the tick species Hyalomma rufipes, a known vector or Crimean-Congo hemorrhagic fever virus, and that birds with an open or wetland habitat have more H. rufipes in comparison to birds with a winter habitat comprising forest and shrubs. The results also suggest a role for birds in the ecology of Alkhurma hemorrhagic fever virus, a hemorrhagic flavivirus, and a potential mechanism for dispersal of the virus to new regions, including Europe and Asia Minor. The results did not provide evidence for immature ticks of the Hyalomma marginatum complex and birds having a major role in the ecology and northward dispersal of tick-borne Anaplasma phagocytophilum, a zoonotic bacterium causing febrile illness in humans and domestic animals. However, the results give support to the idea of a divergent enzootic cycle of A. phagocytophilum involving birds as hosts. Finally, the results of this thesis suggest that H. rufipes do not serve as vectors or contribute to the transmission of the tularemia-causing bacterium Francisella tularensis and that migratory birds do not contribute to northward dispersal of F. tularensis-infected ticks. However, the results suggest that migratory birds contribute to northward dispersal of H. rufipes carrying both Francisella and spotted fever group Rickettsia species, including Francisella-like endosymbionts and Rickettsia aeschlimannii. In conclusion, this thesis helps to clarify the knowledge about the dispersal of ticks and the microorganisms they carry by northbound migrating birds in the African-Western Palaearctic region. Furthermore, it highlights the need of establishing surveillance programs for monitoring the risk of introduction and establishment of important exotic tick species, such as H. rufipes, and tick-borne pathogens in the Western Palaearctic.
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| 7. |
- Lindblom, Anders, 1957-
(author)
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Spotted Fever Rickettsioses in Sweden : Aspects of Epidemiology, Clinical Manifestations and Co-infections
- 2016
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Doctoral thesis (other academic/artistic)abstract
- The spotted fever group rickettsiae are emerging diseases. They cause damage in their hosts by invading the endothelium in small to medium-sized blood vessels, which results in vasculitis that can cause clinical manifestations from most organs.The present thesis describes the prevalence of Rickettsia helvetica in ticks, the incidence of rickettsial infection based on seroreactivity and seroconversion in humans and their symptoms, from different parts of Sweden and the Åland Islands in Finland. This was accomplished through serological analysis of both retrospective and prospective serum samples from confirmed and suspected tick-bitten individuals compared to individuals with no knowledge of tick exposure (blood donors). We found a comparable seroprevalence to Rickettsia spp. in different geographical areas where ticks are present; it was also comparable to the seroprevalence of Borrelia spp. Seroprevalence was also more common, as suspected, in the tick-exposed group compared to blood donors. In comparison with co-infections with other tick-borne infections (Anaplasma spp. and Borrelia spp.), we could conclude that co-infections do exist and that, based on clinical findings, it is difficult to distinguish which microorganism causes certain clinical manifestations. For reliable conclusions regarding the causative microorganism, the diagnosis should basically rely on diagnostic tests. In comparison with Borrelia spp., seroconversion to Rickettisa spp. was more common in the areas we investigated, indicating that rickettsiosis is a common tick-borne infection in Sweden and most likely underdiagnosed.When investigating patients with meningitis, we found R. felis in cerebrospinal fluid from two patients with subacute meningitis. This was the first report in which R. felis was found and diagnosed in patients in Sweden. The patients recovered without sequelae and without causal treatment. To provide guidelines on when to treat Rickettisa spp. infections, more investigations are needed.The present thesis shows that Rickettsia spp. are common in ticks and do infect humans. Rickettsial infection should be considered in both non-specific or specific symptoms after a tick bite. It was also shown in the thesis that flea-borne rickettsiosis (R. felis) occurs in Sweden and may cause invasive infections
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| 8. |
- Sütterlin, Susanne
(author)
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Aspects of Bacterial Resistance to Silver
- 2015
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Doctoral thesis (other academic/artistic)abstract
- Bacterial resistance to antibiotics has increased rapidly within recent years, and it has become a serious threat to public health. Infections caused by multi-drug resistant bacteria entail higher morbidity, mortality, and a burden to health care systems. The use of biocides, including silver compounds, may affect the resistance to both biocides and antibiotics and, thereby, can be a driving factor in this development.The aim of the following thesis was to investigate the frequency of silver resistance and the effects of silver exposure on bacterial populations being of clinical significance and from geographically different parts of the world. Furthermore, it explored the genetic background of silver resistance, and if silver could select directly or indirectly for antibiotic resistance.By a range of methods, from culture in broth to whole genome sequencing, bacterial populations from humans, birds and from the environment were characterized.The studies showed that sil genes, encoding silver resistance, occurred at a high frequency. Sil genes were found in 48 % of Enterobacter spp., in 41 % of Klebsiella spp. and in 21 % of all human Escherichia coli isolates with production of certain types of extended-spectrum beta-lactamases (CTX-M-14 and CTX-M-15). In contrast, silver resistance was not found in bird isolates or in bacterial species, such as Pseudomonas aeruginosa and Legionella spp., with wet environments as their natural habitat. One silver-resistant Enterobacter cloacae strain was isolated from a chronic leg ulcer after only three weeks of treatment with silver-based dressings. The in-vivo effects of these dressings were limited, and they failed to eradicate both Gram-positive and Gram-negative bacteria. The activity of silver nitrate in vitro was bacteriostatic on Gram-positive species such as S. aureus and bactericidal on Gram-negative species. In Enterobacteriaceae, sil genes were associated with silver resistance phenotypes in all but one case. Using whole genome sequencing, single nucleotide polymorphisms in the silS gene were discovered after silver exposure in isolates with expressed silver resistance. This resistance could co-select for resistance to beta-lactams, co-trimoxazole and gentamicin.The findings of this thesis indicate that silver exposure may cause phenotypic silver resistance, and it may reduce the susceptibility to mainly beta-lactams and select for bacteria with resistance to clinically important antibiotics.
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| 9. |
- Svahn, Stefan, 1977-
(author)
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Analysis of Secondary Metabolites from Aspergillus fumigatus and Penicillium nalgiovense : Antimicrobial Compounds from Filamentous Fungi Isolated from Extreme Environments
- 2015
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Doctoral thesis (other academic/artistic)abstract
- This thesis describes the cultivation and extraction of filamentous fungi isolated from extreme environments in the search for new antibiotic compounds. Filamentous fungi are a rich source of medicines including antibiotics, and it is believed that many currently unknown fungal species and bioactive fungal metabolites remain to be discovered.Aspergillus fumigatus and Penicillium nalgiovense strains were isolated from an antibiotic-contaminated riverbed near Hyderabad, India, and soil taken from a penguin’s nest on Paulete Island, Antarctica, respectively. It was anticipated that the extreme conditions within these environments would exert unusual selective pressures on their filamentous fungi, possibly causing the secretion of new bioactive compounds.The cultivation, extraction and analysis of metabolites from the A. fumigatus strain resulted in the isolation of the antimicrobial substance gliotoxin. Subsequent investigations revealed that this strain’s secretion of gliotoxin was increased by as much as 65 % when it was cultivated in the presence of pathogen-associated molecular patterns. These results indicate the existence of a fungal receptor/signaling system for detecting nearby bacteria. The scope for using gliotoxin and the related metabolite bis(methyl)gliotoxin as biomarker metabolites for diagnosing the lethal pulmonary condition invasive aspergillosis was also investigated. Bronchoalveolar lavage fluid from 42 patients with and without possible invasive aspergillosis was extracted and analyzed. The results obtained suggest that gliotoxin and bis(methyl)gliotoxin are not suitable markers for diagnosing invasive aspergillosis.Studies on the P. nalgiovense strain from Antarctica resulted in the isolation of the antifungal agent amphotericin B. The secretion of this compound increased when P. nalgiovense was cultured on a potato-dextrose agar enriched with coconut flakes rather than liquid RPMI 1640 medium. This was the first time amphotericin B was isolated from any organism other than the bacterium Streptomyces nodosus.The results presented in this thesis will be useful in the continuing search for novel bioactive compounds, the diagnosis of fungal infections, and as a source of insight into the interactions between microorganisms. Moreover, they show that even extensively studied fungal genera such as Aspergillus and Penicillium are not completely understood and may produce unexpected or previously unknown bioactive metabolites under appropriate conditions.
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| 10. |
- Wagrell, Sofia
(author)
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Drivers and Hindrances to Med-Tech Innovation : A device's guide to the Swedish healthcare galaxy
- 2017
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Doctoral thesis (other academic/artistic)abstract
- Today, the expectations on new medical technology solutions are substantial. On the one hand, healthcare policy expects new technologies both to improve the quality of people’s life and to reduce the burgeoning healthcare costs. On the other hand, innovation policy expects new med-tech solutions to stimulate economic growth, with large emphasis on the production of new solutions. However, despite the growing importance of med-tech innovations it is cumbersome to embed these innovative promising products into use in the Swedish healthcare sector.This thesis investigates med-tech innovation by following a microwave-based device in the treatment of the common disease BPH, Benign Prostatic Enlargement. This is an empirically based longitudinal study where the microwave device is used as a probe to capture a med-tech innovation journey. We follow the device through the efforts of technological and scientific development, through complex industrial production structures and foremost inits struggles to achieve widespread use in Swedish public healthcare.This study identifies a number of hindrances and drivers and, importantly, how they are interconnected in the innovation process. By applying the different settings of development, production and use of this device, a central finding is that the very same mechanisms can have contradicting effects in the different settings. Moreover, what functions as a trigger to innovation during development, can become later a hindrance to use. The study also shows that, whereas drivers prevail over hindrances in the development and production of med-tech solutions, hindrances clearly prevail in their use, which involves the provision of healthcare services. Not only has the use setting a generally weak financial support, but its organisational structures and regulations do also have a negative impact on the spread of new solutions in healthcare.
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