| 1. |
- Zubair, Saima, et al.
(författare)
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Complete genome sequence of Staphylococcus aureus, strain ILRI_Eymole1/1, isolated from a Kenyan dromedary camel
- 2015
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Ingår i: Standards in Genomic Sciences. - : Springer Science and Business Media LLC. - 1944-3277. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- We report the genome of a Staphylococcus aureus strain (ILRI_Eymole1/1) isolated from a nasal swab of a dromedary camel (Camelus dromedarius) in North Kenya. The complete genome sequence of this strain consists of a circular chromosome of 2,874,302 bp with a GC-content of 32.88 %. In silico annotation predicted 2755 protein-encoding genes and 76 non-coding genes. This isolate belongs to MLST sequence type 30 (ST30). Phylogenetic analysis based on a subset of 283 core genes revealed that it falls within the human clonal complex 30 (CC30) S. aureus isolate cluster but is genetically distinct. About 79 % of the protein encoding genes are part of the CC30 core genome (genes common to all CC30 S. aureus isolates), similar to 18 % were within the variable genome (shared among multiple but not all isolates) and similar to 3 % were found only in the genome of the camel isolate. Among the 85 isolate-specific genes, 79 were located within putative phages and pathogenicity islands. Protein encoding genes associated with bacterial adhesion, and secretory proteins that are essential components of the type VII secretion system were also identified. The complete genome sequence of S. aureus strain ILRI_Eymole1/1 has been deposited in the European Nucleotide Archive under the accession no LN626917.1.
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| 2. |
- Bereczky, Sándor, et al.
(författare)
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Multiclonal asymptomatic Plasmodium falciparum infections predict a reduced risk of malaria disease in a Tanzanian population
- 2007
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Ingår i: Microbes and infection. - : Elsevier BV. - 1286-4579 .- 1769-714X. ; 9:1, s. 103-110
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Tidskriftsartikel (refereegranskat)abstract
- Protective immunity to malaria is acquired after repeated exposure to the polymorphic Plasmodium falciparum parasite. Whether the number of concurrent antigenically diverse clones in asymptomatic infections predicts the risk of subsequent clinical malaria needs further understanding. We assessed the diversity of P. falciparum infections by merozoite surface protein 2 genotyping in a longitudinal population based study in Tanzania. The number of clones was highest in children 6–10 years and in individuals with long time to previous anti-malarial treatment. Individual exposure, analysed by circumsporozoite protein antibody levels, was associated with parasite prevalence but not with the number of clones. The risk of subsequent clinical malaria in children free of acute disease or recent treatment was, compared to one clone, reduced in individuals with multiclonal infections or without detectable parasites, with the lowest hazard ratio 0.28 (95% confidence interval 0.10–0.78 Cox regression) for 2–3 clones. The number of clones was not associated with haemoglobin levels. A reduced risk of malaria in asymptomatic individuals with multiclonal persistent P. falciparum infections suggests that controlled maintenance of diverse infections is important for clinical protection in continuously exposed individuals, and needs to be considered in the design and evaluation of new malaria control strategies.
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| 3. |
- Liljander, Anne, et al.
(författare)
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Influences of intermittent preventive treatment and persistent multiclonal Plasmodium falciparum infections on clinical malaria risk
- 2010
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 5:10
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Intermittent preventive treatment (IPT) of malaria involves administration of curative doses of antimalarials at specified time points to vulnerable populations in endemic areas, regardless whether a subject is known to be infected. The effect of this new intervention on the development and maintenance of protective immunity needs further understanding. We have investigated how seasonal IPT affects the genetic diversity of Plasmodium falciparum infections and the risk of subsequent clinical malaria.MATERIAL AND METHODS: The study included 2227 Ghanaian children (3-59 months) who were given sulphadoxine-pyrimethamine (SP) bimonthly, artesunate plus amodiaquine (AS+AQ) monthly or bimonthly, or placebo monthly for six months spanning the malaria transmission season. Blood samples collected at three post-interventional surveys were analysed by genotyping of the polymorphic merozoite surface protein 2 gene. Malaria morbidity and anaemia was monitored during 12 months follow-up.RESULTS: Monthly IPT with AS+AQ resulted in a marked reduction in number of concurrent clones and only children parasite negative just after the intervention period developed clinical malaria during follow-up. In the placebo group, children without parasites as well as those infected with ≥2 clones had a reduced risk of subsequent malaria. The bimonthly SP or AS+AQ groups had similar number of clones as placebo after intervention; however, diversity and parasite negativity did not predict the risk of malaria. An interaction effect showed that multiclonal infections were only associated with protection in children without intermittent treatment.CONCLUSION: Molecular typing revealed effects of the intervention not detected by ordinary microscopy. Effective seasonal IPT temporarily reduced the prevalence and genetic diversity of P. falciparum infections. The reduced risk of malaria in children with multiclonal infections only seen in untreated children suggests that persistence of antigenically diverse P. falciparum infections is important for the maintenance of protective malaria immunity in high transmission settings.
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| 4. |
- Liljander, Anne
(författare)
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Malaria : multiclonal infections and protective immunity
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The mortality and morbidity attributable to malaria remain high in Sub-Saharan Africa, especially among children less than five years of age. In areas of high transmission, immunity to clinical malaria is gradually acquired after repeated exposure to the polymorphic Plasmodium falciparum parasite. Increased knowledge of the interaction between the human host and the genetic diversity of P. falciparum infections is a prerequisite for understanding the mechanisms underlying acquisition of protective malaria immunity, an understanding important for the development of malaria control strategies e.g. vaccines. This thesis has assessed how the genetic diversity of P. falciparum infections affects the risk of clinical malaria and how clearance of asymptomatic infections affects host protection. The thesis also includes establishment/development of a new technique to analyze the genetic diversity of parasite populations. P. falciparum infections were genotyped based on sequence and size polymorphisms of the genes encoding the parasite antigens merozoite surface protein 1 and 2 (msp 1 and 2). A nested PCR method widely used to characterize parasite populations was adapted to fluorescent PCR and capillary electrophoresis in a DNA sequencer. The improved sensitivity and specificity of allelic discrimination forwards this new method as an important tool in molecular epidemiology studies and antimalarial drug trials. Factors associated with the genetic diversity of P. falciparum infections were investigated in different transmission settings in Tanzania, Ghana and Kenya. The number of concurrent clones increased with age in all studies. Individual exposure, analyzed by antibody levels to the circumsporozoite protein, increased with age but was not associated with the number of clones in a high transmission setting in Tanzania. The number of P. falciparum clones was correlated to the individual s subsequent risk of clinical malaria. In Tanzania, the lowest risk was found in asymptomatic children infected with 2-3 clones. In Ghana, intermittent preventive treatment administered during 6 months of the peak malaria season reduced the infection diversity. Although temporary, this reduction affected susceptibility to malaria during the following high transmission season. Infections composed of ≥2 clones again predicted a lower risk of febrile malaria, however only in children given placebo. These findings suggest that persistence of antigenically diverse P. falciparum infections is important for protective immunity and that clearance of multiclonal infections might contribute to the rebound in clinical disease observed after IPT was stopped in some studies. In an area of lower transmission in Kenya, children with ≥ 2 clones had a marked decreased risk of febrile malaria only when the parasites had been cleared with a course of an antimalarial drug. In Kenya, the number of clones was associated with level of exposure. When excluding children who remained uninfected after treatment and thus considered less exposed, the protection associated with multiclonal infections were even more evident and associated with blood stage immunity. A reduced risk of malaria in asymptomatic individuals with persistent multiclonal P. falciparum infections suggests that controlled maintenance of diverse infections is important for clinical protection in continuously exposed individuals. The findings need to be considered in the design and evaluation of new malaria control strategies such as vaccines and interventions aiming to clear asymptomatic infections.
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| 5. |
- Schieck, Elise, et al.
(författare)
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High antibody titres against predicted Mycoplasma surface proteins do not prevent sequestration in infected lung tissue in the course of experimental contagious bovine pleuropneumonia
- 2014
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Ingår i: Veterinary Microbiology. - : Elsevier BV. - 0378-1135 .- 1873-2542. ; 172:1-2, s. 285-293
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Tidskriftsartikel (refereegranskat)abstract
- Contagious bovine pleuropneumonia (CBPP), a severe respiratory disease of cattle caused by Mycoplasma mycoides subsp. mycoides (Mmm) is endemic in many African countries due to fragmented veterinary services and the lack of an efficient vaccine and sensitive diagnostics. More efficient tools to control the disease are needed, but to develop the tools, a better understanding of host-pathogen interactions is necessary. The aim of this study was to characterize the kinetics of the humoral immune response against 65 Mmm surface antigens for an extended period in cattle that survived a primary infection with Mmm. We describe clinical and haematological outcomes, and dissect the humoral immune response over time, to specific antigens and compared the antibody responses between different pathomorphological outcomes. No antigen-specific antibodies correlating with protection were identified. Interestingly we found that animals that developed MycopIasma-containing sequestra had significantly higher antibody levels against proteins comprising the surface proteome than the animals that cleared Mycoplasma from their lungs. Based on these data we suggest that high antibody titres might play a role in the establishment of pathomorphological changes, such as vasculitis, which should be investigated in future studies. Beneficial antibody specificities and cellular immune responses need to be identified in order to foster the development of an improved vaccine in the future.
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