uu.seUppsala University Publications
Change search
Refine search result
1 - 39 of 39
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1. Al-Saai, Salma
    et al.
    Kheir, Amany
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Abdel-Muhsin, Abdel-Muhsin A
    Al-Ghazali, Aisha
    Nwakanma, Davis
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Babiker, Hamza A
    Distinct haplotypes of dhfr and dhps among Plasmodium falciparum isolates in an area of high level of sulfadoxine-pyrimethamine (SP) resistance in eastern Sudan2009In: Infection, Genetics and Evolution, ISSN 1567-1348, E-ISSN 1567-7257, Vol. 9, no 5, 778-783 p.Article in journal (Refereed)
    Abstract [en]

    Typing of polymorphic microsatellites that are linked to drug resistance genes has shed light on the origin and pattern of spread of some anti-malarial drugs. Recent surveys revealed spread of a high-level pyrimethemine resistant lineage of Plasmodium falciparum, of Asian origin, across Africa. Here, we examined mutations in dihydrofolate reductase, dhfr [chromsosome 4], the dihydropteroate synthase, dhps [chromosome 8] associated with resistance to sulfadoxine-pyrimethamine (SP), and neighboring microsatellites among P. falciparum isolates in Asar village, eastern Sudan. This area lies at the fringes of malaria endemicity, where the remote P. falciparum parasites have some distinct genetic characteristics. Overall, 89% (84/94) of the examined isolates carried double mutations at dhfr (N51I and S108N), but the 59R and I164L mutations were not seen. Similarly, the majority, 43% (35/81) of the isolates carried double mutations at dhps (437G, 540E). Analysis of neighboring microsatellites revealed one major dhfr haplotype with mutations (51I, 108N) and one dhps haplotype with mutations (436S, 437G, 540E). These haplotypes differ from the major ones thought to drive resistance to SP across Africa. The resistant haplotypes of dhfr and dhps, in Asar, share some microsatellites with the wild genotypes suggesting that they were generated locally. Among isolates successfully examined, 40% shared identical haplotypes of the 2 loci, comprising a dominant resistant lineage. Undoubtedly, this lineage plays an important role in clinical failure to SP in this area.

  • 2. Arakere, Gayathri
    et al.
    Nadig, Savitha
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Swedberg, Göte
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Macaden, Ragini
    Amarnath, Satish K
    Raghunath, Dasarathy
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Genotyping of methicillin-resistant Staphylococcus aureus strains from two hospitals in Bangalore, South India.2005In: J Clin Microbiol, ISSN 0095-1137, Vol. 43, no 7, 3198-202 p.Article in journal (Other scientific)
  • 3. Babiker, Hamza A.
    et al.
    Hastings, Ian M.
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Impaired fitness of drug-resistant malaria parasites: evidence and implication on drug-deployment policies2009In: Expert review of anti-infective therapy, ISSN 1478-7210, Vol. 7, no 5, 581-593 p.Article, review/survey (Refereed)
    Abstract [en]

    Malaria, a leading parasitic disease, inflicts an enormous toll on human lives and is caused by protozoal parasites belonging to the genus Plasmodium. Antimalarial drugs targeting essential biochemical processes in the parasite are the primary resources for management and control. However, the parasite has established mutations, substantially reducing the efficacy of these drugs. First-line therapy is faced the with the consistent evolution of drug-resistant genotypes carrying these mutations. However, drug-resistant genotypes are likely to be less fit than the wild-type, suggesting that they might disappear by reducing the volume of drug pressure. A substantial body of epidemiological evidence confirmed that the frequency of resistant genotypes wanes when active drug selection declines. Drug selection on the parasite genome that removes genetic variation in the vicinity of drug-resistant genes (hitch-hiking) is common among resistant parasites in the field. This can further disadvantage drug-resistant strains and limit their variability in the face of a mounting immune response. Attempts to provide unequivocal evidence for the fitness cost of drug resistance have monitored the outcomes of laboratory competition experiments of deliberate mixtures of sensitive and resistant strains, in the absence of drug pressure, using isogenic clones produced either by drug selection or gene manipulation. Some of these experiments provided inconclusive results, but they all suggested reduced fitness of drug-resistant clones in the absence of drug pressure. In addition, biochemical analyses provided clearer information demonstrating that the mutation of some antimalarial-targeted enzymes lowers their activity compared with the wild-type enzyme. Here, we review current evidences for the disadvantage of drug-resistance mutations, and discuss some strategies of drug deployment to maximize the cost of resistance and limit its spread.

  • 4. Buwembo, William
    et al.
    Aery, Sahil
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Rwenyonyi, Charles
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Kironde, Fred
    Point Mutations in the folP Gene Partly Explain Sulfonamide Resistance of Streptococcus mutans2013In: International Journal of Microbiology, ISSN 1687-918X, E-ISSN 1687-9198, Vol. 2013, 367021- p.Article in journal (Refereed)
  • 5.
    Enweji, Nizar
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Kheri, Amani
    Kerje, Susanne
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Abdel-Muhsin, Abdel-Muhsin
    Babiker, Hamza
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Dynamics of asymptomatic malaria infections as revealed by microsatellite typingManuscript (preprint) (Other academic)
  • 6. Eriksen, J
    et al.
    Mwankusye, S
    Mduma, S
    Kitua, A
    Swedberg, G
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Tomson, G
    Gustafsson, L L
    Warsame, M
    Patterns of resistance and DHFR/DHPS genotypes of Plasmodium falciparum in rural Tanzania prior to the adoption of sulfadoxine-pyrimethamine as first-line treatment.2004In: Trans R Soc Trop Med Hyg, ISSN 0035-9203, Vol. 98, no 6, 347-53 p.Article in journal (Refereed)
  • 7. Eriksen, J
    et al.
    Mwankusye, S
    Mduma, S
    Veiga, M I
    Kitua, A
    Tomson, G
    Petzold, M G
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Gustafsson, L L
    Warsame, M
    Antimalarial resistance and DHFR/DHPS genotypes of Plasmodium falciparum three years after introduction of sulfadoxine-pyrimethamine and amodiaquine in rural Tanzania.2008In: Transactions of the Royal Society of Tropical Medicine and Hygiene, ISSN 0035-9203, E-ISSN 1878-3503, Vol. 102, no 2, 137-142 p.Article in journal (Refereed)
    Abstract [en]

    We assessed the efficacy of sulfadoxine-pyrimethamine (SP) and amodiaquine (AQ) and DHFR/DHPS genotypes of Plasmodium falciparum in rural Tanzania, 3 years after their introduction as first- and second-line treatments for uncomplicated malaria, respectively. Under five children with uncomplicated malaria were given standard treatments of either SP (n=66) or AQ (n=30) and treatment outcomes after 14 and 28 days were determined. Total treatment failure of 18 and 42.5% was observed for SP on days 14 and 28, respectively. For AQ, total treatment failure of 27 and 53% was found on day 14 and 28, respectively. On day 14, significantly lower SP total treatment failures were observed in 2004 compared with results from a study conducted in 1999 in the same location. No relationship was detected between clinical outcome and DHFR/DHPS genotypes, but the point mutation prevalence in parasites was higher than in 1999. Pre-treatment blood levels of SP were detected in a quarter of the study children: less than expected. We report unacceptably high levels of total treatment failures, both for first- and second-line treatments for uncomplicated malaria in Tanzania 3 years after their introduction, supporting the decision to replace them with artemisinin-based combination therapy.

  • 8. Golassa, Lemu
    et al.
    Baliraine, Frederick N.
    Enweji, Nizar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Erko, Berhanu
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Aseffa, Abraham
    Microscopic and molecular evidence of the presence of asymptomatic Plasmodium falciparum and Plasmodium vivax infections in an area with low, seasonal and unstable malaria transmission in Ethiopia2015In: BMC Infectious Diseases, ISSN 1471-2334, E-ISSN 1471-2334, Vol. 15, 310Article in journal (Refereed)
    Abstract [en]

    Background: The presence of asymptomatic infections has serious implications for malaria elimination campaigns. Since asymptomatic carriers do not seek treatment for their infection and may become gametocyte carriers, they undoubtedly contribute to the persistence of malaria transmission in a population. The presence of asymptomatic parasitemias was noted in areas with seasonal malaria transmission. In Ethiopia there is a paucity of data regarding the prevalence of asymptomatic malaria carriage. This study was undertaken to assess the presence and prevalence of asymptomatic Plasmodium falciparum and Plasmodium vivax infections in south-central Oromia, Ethiopia. Methods: A total of 1094 apparently healthy individuals >= 2 years of age in south-central Oromia, Ethiopia, an area with seasonal and unstable malaria transmission, were screened for the presence of asymptomatic plasmodial infections. Finger-prick blood samples were taken from each participant for blood film preparation for microscopy and the rapid diagnostic test (RDT). Blood samples were also spotted on Whatman 3MM filter paper for parasite DNA extraction. Results: The prevalence of asymptomatic Plasmodium carriage (P. falciparum, P. vivax and mixed species) was 5.0 % (55/1,094) as determined by microscopy, while the prevalence as determined using RDT was 8.2 % (90/1,094). PCR was done on 47 of 55 microscopy-confirmed and on 79 of 90 RDT-confirmed samples. PCR detected parasite DNA in 89.4 % (42/47) of the microscopy-positive samples and in 77.2 % (61/79) of the RDT-positive samples. No significant difference was observed in the prevalence of asymptomatic P. falciparum or P. vivax infections in the study area (P > 0.1). However, the prevalence of asymptomatic parasitaemia was significantly associated with gender (OR = 0.47, P = 0.015; being higher in males than females) and age (X-2 = 25, P < 0.001; being higher in younger than in older individuals). Age and parasite densities had an inverse relationship. Conclusions: This study confirms the presence of asymptomatic P. falciparum and P. vivax infections in south-central Oromia, an area with low, seasonal and unstable malaria transmission in Ethiopia. Of 55 microscopically confirmed asymptomatic infections, P. falciparum monoinfection accounted for 45.5 % and of 90 RDT positive asymptomatic infections, 66.7 % were P. falciparum. Although not statistically significant, P. falciparum accounted for a relatively large number of the asymptomatic infections as determined by both tests. The prevalence of asymptomatic parasitaemia was highest in the younger age group. HRP-2-based RDTs specific for P. falciparum showed high false positivity rate compared to Plasmodium lactate dehydrogenase (pLDH) specific to P. vivax. Although microscopy and RDT detected substantial numbers of asymptomatic infections in apparently healthy inhabitants, the use of a highly sensitive molecular diagnostics offers a more accurate assessment of the magnitude of asymptomatic infections.

  • 9. Golassa, Lemu
    et al.
    Enweji, Nizar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Erko, Berhanu
    Aseffa, Abraham
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Detection of a substantial number of sub-microscopic Plasmodium falciparum infections by polymerase chain reaction: a potential threat to malaria control and diagnosis in Ethiopia2013In: Malaria Journal, ISSN 1475-2875, E-ISSN 1475-2875, Vol. 12, 352- p.Article in journal (Refereed)
    Abstract [en]

    Background: Prompt and effective malaria diagnosis not only alleviates individual suffering, but also decreases malaria transmission at the community level. The commonly used diagnostic methods, microscopy and rapid diagnostic tests, are usually insensitive at very low-density parasitaemia. Molecular techniques, on the other hand, allow the detection of low-level, sub-microscopic parasitaemia. This study aimed to explore the presence of sub-microscopic Plasmodium falciparum infections using polymerase chain reaction (PCR). The PCR-based parasite prevalence was compared against microscopy and rapid diagnostic test (RDT). Methods: This study used 1,453 blood samples collected from clinical patients and sub-clinical subjects to determine the prevalence of sub-microscopic P. falciparum carriages. Subsets of RDT and microscopy negative blood samples were tested by PCR while all RDT and microscopically confirmed P. falciparum-infected samples were subjected to PCR. Finger-prick blood samples spotted on filter paper were used for parasite genomic DNA extraction. Results: The prevalence of sub-microscopic P. falciparum carriage was 19.2% (77/400) (95% CI = 15.4-23.1). Microscopy-based prevalence of P. falciparum infection was 3.7% (54/1,453) while the prevalence was 6.9% (100/1,453) using RDT alone. Using microscopy and PCR, the estimated parasite prevalence was 20.6% if PCR were performed in 1,453 blood samples. The prevalence was estimated to be 22.7% if RDT and PCR were used. Of 54 microscopically confirmed P. falciparum-infected subjects, PCR detected 90.7% (49/54). Out of 100 RDT-confirmed P. falciparum infections; PCR detected 80.0% (80/100). The sensitivity of PCR relative to microscopy and RDT was, therefore, 90.7% and 80%, respectively. The sensitivity of microscopy and RDT relative to PCR was 16.5 (49/299) and 24.2% (80/330), respectively. The overall PCR-based prevalence of P. falciparum infection was 5.6- and 3.3 fold higher than that determined by microscopy and RDT, respectively. None of the sub-microscopic subjects had severe anaemia, though 29.4% had mild anaemia (10-11.9 g/dl). Conclusions: Asymptomatic, low-density malaria infection was common in the study area and PCR may be a better tool for measuring Plasmodium prevalence than microscopy and RDT. The inadequate sensitivity of the diagnostic methods to detect substantial number of sub-microscopic parasitaemia would undoubtedly affect malaria control efforts, making reduction of transmission more difficult. RDT and microscopy-based prevalence studies and subsequent reports of reduction in malaria incidence underestimate the true pictures of P. falciparum infections in the community. PCR, on the other hand, seems to have reasonable sensitivity to detect a higher number of infected subjects with low and sub-microscopic parasite densities than RDTs or microscopy.

  • 10. Golassa, Lemu
    et al.
    Enweji, Nizar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Erko, Berhanu
    Aseffa, Abraham
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    High prevalence of pfcrt-CVIET haplotype in isolates from asymptomatic and symptomatic patients in south-central Oromia, Ethiopia2014In: Malaria Journal, ISSN 1475-2875, E-ISSN 1475-2875, Vol. 13, 120- p.Article in journal (Refereed)
    Abstract [en]

    Background: As a result of extensive chloroquine resistance (CQR) in Plasmodium falciparum in late 1990s, Ethiopia replaced CQ with sulphadoxine-pyrimethamine (SP) as first-line drug, which in turn was replaced by artemisinin combination therapy in 2004. Plasmodium falciparum resistance to CQ is determined by the mutation at K76T of the P. falciparum chloroquine resistance transporter (pfcrt) gene. Understanding diversity in the P. falciparum genome is crucial since it has the potential to influence important phenotypes of the parasite such as drug resistance. Limited data is available regarding the type of pfcrt mutant allelic type, the effect of CQ withdrawal and diversity of the parasite population in south-central Oromia, Ethiopia. Methods: Finger-pricked blood spotted on Whatman 3MM filter papers were collected from falciparum malaria patients. Parasite DNA was extracted from individual blood spots on the filter papers. The presence of K76T mutations was determined using nested PCR for all isolates. Complete sequencing of mutations in pfcrt 72-76 was done for a set of randomly selected resistant isolates. Four microsatellite (MS) markers were analysed to determine the heterozygosity. Results: Although CQ was withdrawn for more than a decade, 100% of the parasites still carried the pfcrt K76T mutation. All isolates were mutant at the K76T polymorphism. Based on combinations of MS markers, seven different Ethiopian CQR variants (E1-E7) were identified. Heterozygosity (He) for MS flanking the pfcrt chloroquine resistance allele ranged from 0.00 (mscrt -29, -29.268 kb) to 0.21 (mscrt -2, -2.814 kb). H-e ranged from 0.00 (msint 3, 0 kb) to 0.19 (msint 2, 0 kb) for MS within the pfcrt gene. Both intronic and MS flanking the pfcrt gene showed low levels of diversity. Conclusion: pfcrt CQR allele seems to be fixed in the study area. Of the different haplotypes associated with CQR, only the CVIET genotype was identified. No reversal to the wild-type has occurred in Ethiopia unlike in many Africa countries where CQR parasites declined after cessation of CQ use. Decreased diversity in CQR isolates surrounding pfcrt suggests CQ selection and homogenization among CQR parasite population. While mutation in msint 3 and mscrt -29 of the mutant pfcrt allele is being fixed, it seems that mutations in msint 2 and mscrt -2 are still evolving and may indicate the start of re-diversification of the population from a fixed 76 T population.

  • 11. Golassa, Lemu
    et al.
    Erko, Berhanu
    Baliraine, Frederick N.
    Aseffa, Abraham
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Polymorphisms in chloroquine resistance-associated genes in Plasmodium vivax in Ethiopia2015In: Malaria Journal, ISSN 1475-2875, E-ISSN 1475-2875, Vol. 14, 164Article in journal (Refereed)
    Abstract [en]

    Background: Evidence for decreasing chloroquine (CQ) efficacy against Plasmodium vivax has been reported from many endemic countries in the world. In Ethiopia, P. vivax accounts for 40% of all malaria cases and CQ is the first-line drug for vivax malaria. Mutations in multidrug resistance 1 (pvmdr-1) and K10 insertion in the pvcrt-o genes have been identified as possible molecular markers of CQ-resistance (CQR) in P. vivax. Despite reports of CQ treatment failures, no data are currently available on the prevalence of molecular markers of P. vivax resistance in Ethiopia. The objective of this study was to determine the prevalence of mutations in the pvmdr-1 and K10 insertion in the pvcrt-o genes. Methods: A total of 36 P. vivax clinical isolates were collected from West Arsi district in Ethiopia. Sequencing was used to analyse polymorphisms of the pvcrt-o and pvmdr-1 genes. Results: Sequencing results of the pvmdr-1 fragment showed the presence of two non-synonymous mutations at positions 976 and 1076. The Y -> F change at codon 976 (TAC -> TTC) was observed in 21 (75%) of 28 the isolates while the F -> L change (at codon 1076), which was due to a single mutation (TTT -> CTT), was observed in 100% of the isolates. Of 33 samples successfully amplified for the pvcrt-o, the majority of the isolates (93.9%) were wild type, without K10 insertion. Conclusions: High prevalence of mutations in candidate genes conferring CQR in P. vivax was identified. The fact that CQ is still the first-line treatment for vivax malaria, the significance of mutations in the pvcrt-o and pvmdr-1 genes and the clinical response of the patients' to CQ treatment and whether thus an association exists between point mutations of the candidate genes and CQR requires further research in Ethiopia.

  • 12. Golassa, Lemu
    et al.
    Kamugisha, Erasmus
    Ishengoma, Deus S.
    Baraka, Vito
    Shayo, Alex
    Baliraine, Frederick N.
    Enweji, Nizar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Erko, Berhanu
    Aseffa, Abraham
    Choy, Angel
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Identification of large variation in pfcrt, pfmdr-1 and pfubp-1 markers in Plasmodium falciparum isolates from Ethiopia and Tanzania2015In: Malaria Journal, ISSN 1475-2875, E-ISSN 1475-2875, Vol. 14, 264Article in journal (Refereed)
    Abstract [en]

    Background: Plasmodium falciparum resistance to anti-malarials is a major drawback in effective malaria control and elimination globally. Artemisinin-combination therapy (ACT) is currently the key first-line treatment for uncomplicated falciparum malaria. Plasmodium falciparum genetic signatures at pfmdr-1, pfcrt, and pfubp-1 loci are known to modulate in vivo and in vitro parasite response to ACT. The objective of this study was to assess the distribution of these resistance gene markers in isolates collected from different malaria transmission intensity in Ethiopia and Tanzania. Methods: Plasmodium falciparum clinical isolates were collected from different regions of Ethiopia and Tanzania. Genetic polymorphisms in the genes pfcrt, pfmdr-1 and pfubp-1 were analysed by PCR and sequencing. Frequencies of the different alleles in the three genes were compared within and between regions, and between the two countries. Results: The majority of the isolates from Ethiopia were mutant for the pfcrt 76 and wild-type for pfmdr-1 86. In contrast, the majority of the Tanzanian samples were wild-type for both pfcrt and pfmdr-1 loci. Analysis of a variable linker region in pfmdr-1 showed substantial variation in isolates from Tanzania as compared to Ethiopian isolates that had minimal variation. Direct sequencing of the pfubp-1 region showed that 92.8% (26/28) of the Ethiopian isolates had identical genome sequence with the wild type reference P. falciparum strain 3D7. Of 42 isolates from Tanzania, only 13 (30.9%) had identical genome sequences with 3D7. In the Tanzanian samples, 10 variant haplotypes were identified. Conclusion: The majority of Ethiopian isolates carried the main marker for chloroquine (CQ) resistance, while the majority of the samples from Tanzania carried markers for CQ susceptibility. Polymorphic genes showed substantially more variation in Tanzanian isolates. The low variability in the polymorphic region of pfmdr-1 in Ethiopia may be a consequence of low transmission intensity as compared to high transmission intensity and large variations in Tanzania.

  • 13.
    Jönsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Qvarnström, Yvonne
    Engstrand, Lars
    Swedberg, Göte
    Clarithromycin treatment selects for persistent macrolide-resistant bacteria in the throat commensal flora2005In: International Journal of Antimicrobial Agents, Vol. 25, 68-74 p.Article in journal (Refereed)
  • 14.
    Jönsson, Maria
    et al.
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Qvarnström, Yvonne
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Engstrand, Lars
    Department of Medical Sciences.
    Swedberg, Göte
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Clarithromycin treatment selects for persistent macrolide-resistant bacteria in throat commensal flora.2005In: Int J Antimicrob Agents, ISSN 0924-8579, Vol. 25, no 1, 68-74 p.Article in journal (Refereed)
  • 15.
    Jönsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Qvarnström, Yvonne
    Rosenling, Therese
    Swedberg, Göte
    Further characterisation of the bifunctional HPPK-DHPS from Plasmodium falciparumManuscript (Other academic)
  • 16.
    Jönsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Ström, Katrin
    Swedberg, Göte
    Mutations and Horizontal Transmission have Contributed to Sulfonamide Resistance in Streptococcus pyogenes2003In: Microbial Drug Resistance, Vol. 9, no 2, 147-153 p.Article in journal (Refereed)
  • 17.
    Jönsson, Maria
    et al.
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Swedberg, Göte
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Hydroxymethyldihydropterin pyrophosphokinase from Plasmodium falciparum complements a folK-knockout mutant in E. coli when expressed as a separate polypeptide detached from dihydropteroate synthase.2005In: Mol Biochem Parasitol, ISSN 0166-6851, Vol. 140, no 1, 123-5 p.Article in journal (Refereed)
  • 18.
    Jönsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Swedberg, Göte
    Hydroxymethyldihydropterin pyrophosphokinase from Plasmodium falciparum complements a folK-knockout mutant in E. coli when expressed as a separate polypeptide detached fromdihydropteroate synthase2005In: Molecular and Biochemical Parasitology, Vol. 140, 123-125 p.Article in journal (Refereed)
  • 19.
    Jönsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Macrolide resistance can be transferred by conjugation from viridans streptococci to Streptococcus pyogenes2006In: International Journal of Antimicrobial Agents, ISSN 0924-8579, E-ISSN 1872-7913, Vol. 28, no 2, 101-103 p.Article in journal (Refereed)
    Abstract [en]

    Efflux pumps encoded by mef genes are among the most common mechanisms of resistance to macrolides. These genes are often located on horizontally transferable elements such as transposons. We present data indicating conjugative transfer of the mef(E) gene from viridans streptococci to the pathogen Streptococcus pyogenes. The mef(E) gene is located on the previously described MEGA (macrolide efflux genetic assembly) element. Of 110 isolates tested, 85% of those that carried the mef(A/E) gene carried it on MEGA, and in all cases of conjugal transfer of the mef(E) gene it was carried on MEGA. It therefore appears reasonable to draw the conclusion that this element is important in the lateral transfer of macrolide resistance between streptococci.

  • 20. Kamugisha, Erasmus
    et al.
    Bujila, Ioana
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Lahdo, Mona
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Pello-Esso, Samtou
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Minde, Mercy
    Kongola, Gilbert
    Naiwumbwe, Halima
    Kiwuwa, Steven
    Kaddumukasa, Mark
    Kironde, Fred
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Large differences in prevalence of Pfcrt and Pfmdr1 mutations between Mwanza, Tanzania and Iganga, Uganda: a reflection of differences in policies regarding withdrawal of chloroquine?2012In: Acta Tropica, ISSN 0001-706X, E-ISSN 1873-6254, Vol. 121, no 2, 148-151 p.Article in journal (Refereed)
    Abstract [en]

    BACKGROUND:

    Malaria is still a major public health problem in the world and sub-Saharan Africa is one of the most affected areas. Efforts to control malaria are highly affected by drug resistance to commonly used antimalarials. The introduction of artemisinin based combination therapy (ACT) as a first line drug seems to be a major step in treatment of uncomplicated malaria, though search for drugs to combine with artemisinins still continues. There have been reports on increased prevalence of the wild type markers Pfcrt 76K and Pfmdr1 86N in some African countries and ideas of using chloroquine (CQ) in intermittent presumptive treatment for adults (IPTa) is coming up. The common combination of artemether and lumefantrine even selects for parasites that are wild type at these positions. This study is comparing prevalence of mutation at these two positions in two East African countries with ACT as their first line drug but following somewhat different drug policies regarding CQ. In Tanzania CQ was stopped in 2001 but in Uganda CQ was retained in combination with sulfadoxine-pyrimethamine (SP) and used in home based management of fever for some time. SP is still used in IPT for pregnant women.

    METHODS:

    Blood smears and dried blood spots on Whatman filter papers were collected from 100 patients with uncomplicated malaria in Mwanza, Tanzania and 100 patients from Iganga, Uganda. DNA was extracted from all samples using Tris EDTA method. PCR and RFLP were performed and sequencing done on Pfcrt amplification products.

    RESULTS:

    The prevalence of K76T mutations at Pfcrt in samples from Mwanza, Tanzania was 40.5% (34/84) and 100% (100/100) in samples from Iganga, Uganda. Prevalence of N86Y mutations in Pfmdr1 was 16.9% (13/77) and 77.7% (63/81) in samples from Mwanza and Iganga, respectively. The re-emergence of CQ sensitive isolates in Mwanza, Tanzania showed the haplotype CVMNK typical for wild type isolates.

    CONCLUSIONS:

    The prevalence of CQ resistant parasites in Mwanza, Tanzania is low compared to the existing high level of resistant parasites in Iganga, Uganda. This could be an indication that CQ may become useful in the future in Tanzania. This study shows clearly that there is a difference in mutations at these positions in these two countries implementing similar but somewhat different drug policies. In Uganda the drug resistance has reached fixation while in Tanzania the prevalence is going down.

  • 21. Kamugisha, Erasmus
    et al.
    Jing, Sun
    Minde, Mercy
    Kataraihya, Johaness
    Kongola, Gilbert
    Kironde, Fred
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Efficacy of artemether-lumefantrine in treatment of malaria among under-fives and prevalence of drug resistance markers in Igombe-Mwanza, north-western Tanzania2012In: Malaria Journal, ISSN 1475-2875, E-ISSN 1475-2875, Vol. 11, 58- p.Article in journal (Refereed)
    Abstract [en]

    Background: Drug resistance to anti-malarials is a major public health problem worldwide. This study aimed at establishing the efficacy of artemether-lumefantrine (ACT) in Igombe-Mwanza, north-western Tanzania after a few years of ACT use, and establish the prevalence of mutations in key targets for artemisinin, chloroquine and sulphadoxine/pyrimetamine (SP) drugs. Methods: A prospective single cohort study was conducted at Igombe health centre using artemether-lumefantrine combination therapy between February 2010 and March 2011. The follow-up period was 28 days and outcome measures were according to WHO guidelines. Blood was collected on Whatman filter paper for DNA analysis. DNA extraction was done using TRIS-EDTA method, and mutations in Pfcrt, Pfmdr1, Pfdhfr, Pfdhps and Pfatp6 were detected using PCR-RFLP methods established previously. Results: A total of 103 patients completed the 28 days follow-up. The mean haemoglobin was 8.9 g/dl (range 5.0 to 14.5 g/dl) and mean parasite density was 5,608 parasites/mu l. Average parasite clearance time was 34.7 hours and all patients cleared the parasites by day 3. There was no early treatment failure in this study. Late clinical failure was seen in three (2.9%) patients and late parasitological failure (LPF) was seen in two (1.9%). PCR-corrected LPF was 1% and adequate clinical and parasitological response was 96%. The majority of parasites have wild type alleles on pfcrt 76 and pfmdr1 86 positions being 87.8% and 93.7% respectively. Mutant parasites predominated at pfdhfr gene at the main three positions 108, 51 and 59 with prevalence of 94.8%, 75.3% and 82.5% respectively. Post-treatment parasites had more wild types of pfdhps at position 437 and 540 than pre-treatment parasites. No mutation was seen in pfatp6 769 in re-infecting or recrudescing parasites. Conclusion: The efficacy of artemether-lumefantrine for treatment of uncomplicated malaria is still high in the study area although the rate of re-infection is higher than previously reported. Parasite clearance after 48 hours was lower compared to previous studies. The prevalence of wild type allele pfcrt 76 K and pfmdr1 86 N was high in the study area while markers for SP resistance is still high. Artemether-lumefantrine may be selecting for wild type alleles on both positions (437 and 540) of pfdhps.

  • 22. Kamugisha, Erasmus
    et al.
    Sendagire, Hakim
    KadduMukasa, Mark
    Enweji, Nizar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Gheysari, Fatheme
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Kironde, Fred
    Detecting adenosine triphosphatase 6 point mutations that may be associated with Plasmodium falciparum resistance to artemisinin: prevalence at baseline, before policy change in Uganda2011In: Tanzania Journal of Health Research, ISSN 1821-6404, Vol. 13, no 1, 50-60 p.Article in journal (Refereed)
    Abstract [en]

    The artemisinin based combination therapy (ACT) of artemether and lumefantrine (Co-artem) has recently replaced chloroquine and fansidar as the first line treatment policy drug in Uganda. It is necessary to develop practical procedures to monitor the likely emergence and spread of artemisinin resistant P. falciparum strains. We have analyzed the genotypes of PfATP6 in parasites from 300 stored filter paper samples from malaria patients who were diagnosed and treated in the years 1999 to 2004 at three field sites in Uganda. This is a period just prior to introduction of Co-artem. In order to develop a simple molecular procedure for mutation detection, regions of PfATP6 encoding protein domains important in artemisinin binding was amplified by nested PCR. Three DNA products, which together contain most of the coding region of amino acids located within the putative active site of pfATP6 were readily amplified. The amplified DNA was digested by restriction enzymes and the fragments sized by agarose gel electrophoresis. For the important codons 260, 263 and 769, methods using engineered restriction sites were employed. We did not find mutations at codons for the key residues Lys 260, Leu263, Gln266, Ser769 and Asn1039. Nucleotide sequencing of pfATPase6 gene DNA from at least 15 clinical isolates confirmed the above findings and suggested that mutations at these amino acid residues have not emerged in our study sites.

  • 23.
    Kheir, Amany
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Nwakanma, Davis
    Al-Gazali, Aisha
    Akbarova, Yagut
    Al-Saai, Salma
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Babiker, Hamza A.
    Transmission and Cross-Mating of High-Level Resistance Plasmodium falciparum Dihydrofolate Reductase Haplotypes in The Gambia2010In: American Journal of Tropical Medicine and Hygiene, ISSN 0002-9637, E-ISSN 1476-1645, ISSN 20348495, Vol. 82, no 4, 535-541 p.Article in journal (Refereed)
    Abstract [en]

    A high-level pyrimethamine resistance Plasmodium falciparum lineage with triple dihydrofolate reductase (dhfr) mutations prevails across Africa. However, additional minority lineages were seen. We examined transmission success of mutant dhfr haplotypes among 22 children in The Gambia and 60 infected Anopheles gambiae mosquitoes fed on their blood. Additional polymorphic genes of the gametocyte-specific protein (pfg377) and merozoite surface protein-1 (MSP-1) were examined. Similarities were seen between pfg377 and MSP-1 alleles in children and mosquitoes and evidence of cross-mating between different parasite genotypes was seen in some infected mosquitoes, reflecting high transmission success of existing clones. With regard to dhfr, 16 haplotypes were seen among the children: 2 carried double mutations and 14 carried triple mutations. However, only nine haplotypes, all with triple mutations, were detected among mosquitoes. A single triple-mutant dhfr haplotype, similar to that in other countries in Africa, predominated among children (42%) and mosquitoes (60%), supporting the hypothesis of migration of this haplotype across Africa. However, evidence of cross-mating between the above haplotypes signifies the role of local evolution.

  • 24.
    Kheir, Amany
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Villalta, Tamara
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Nasser, Elkhansa
    Abdel-Muhsin, Abdel-Muhsin
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Babiker, Hamza
    Fitness cost of drug resistance in malaria parasitesManuscript (preprint) (Other academic)
    Abstract [en]

    Version:1.0 StartHTML:0000000186 EndHTML:0000006024 StartFragment:0000002654 EndFragment:0000005988 SourceURL:file://localhost/Users/gotes/Desktop/Amany%20disp/Paper%20IV-2011.doc @font-face { font-family: "Times New Roman"; }@font-face { font-family: "Times New Roman Italic"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman"; }table.MsoNormalTable { font-size: 10pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; }

    Many field surveys have demonstrated a decline in the prevalence of drug resistant parasites following withdrawal of drugs, implying fitness cost of mutations causing resistance. However, for clear ethical reason, within-host dynamics of drug-resistant mutants and sensitive forms in the absence of the drug has not been investigated in nature.   Here we monitored longevity of drug resistant Plasmodium falciparum parasites in a small village in eastern Sudan with a long dry period followed by a brief annual rains and appearance of Anopheles mosquitoes. This allows tracing the fate of drug resistant P. falciparum clones, in the absence of selective drug pressure, over a period of 7 to 8 months, in the dry season. Two cohorts were examined, (a) 83 patients enrolled in October 1993 and monitored to December 1994, and (b) 121 patients recruited in October 2001 and followed-up to December 2002. Patients in both cohorts were treated, on diagnosis, with chloroquine (25mg/kg) and then followed monthly, in each visit a blood sample was collected and  a patient was treated only if fever and visible parasitaemia were detected. We used PCR and RT-PCR to detect parasites and gametocytes that persisted at sub-patent levels in the dry season, respectively. In addition, we examined alleles of genes controlling the response of P. falciparum to chloroquine; the chloroquine resistance transporter (Pfcrt76T) and the multi-drug resistance protein (Pfmdr186Y).  A large proportion of both cohorts maintained gametocytes producing sub-patent asymptomatic P. falciparum infections throughout the dry season. Mutant alleles of Pfcrt76T reached fixation following CQ treatment and remained high in the transmission season, a reflection of selection. However, at the start of the dry season, wild type alleles of both genes (Pfcrt76K and Pfmdr186N) started to emerge and increased significantly in frequency as the season progressed. Some members of both cohorts, encountered malaria episode in the ensuing transmission season, all of them were found to harbour parasite with wild type alleles for both genes.  The above data has clearly shown selective disadvantage of CQ resistant genotypes (Pfcrt76T, Pfmdr186Y) in the absence of the drug. The data were discussed in the context of fitness of drug resistant parasite and its epidemiological impact.

  • 25.
    Lwanira, Catherine N.
    et al.
    Makerere Univ, Coll Hlth Sci, Sch Biomed Sci, Kampala, Uganda..
    Mukasa, Mark Kaddu
    Makerere Univ, Coll Hlth Sci, Sch Med, Kampala, Uganda..
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Kironde, Fred
    Makerere Univ, Coll Hlth Sci, Sch Biomed Sci, Kampala, Uganda.;Islamic Univ Uganda IUIU, Fac Hlth Sci, Habib Med Sch, Kampala, Uganda..
    Frequency of RANTES gene polymorphisms and their association with incidence of malaria: a longitudinal study on children in Iganga district, Uganda2015In: Malaria Journal, ISSN 1475-2875, E-ISSN 1475-2875, Vol. 14, 341Article in journal (Refereed)
    Abstract [en]

    Background: The severity and outcome of malaria is influenced by host immunity in which chemokines such as Regulated upon Activation, Normal T cell Expressed and Secreted (RANTES) play an important role. Previous studies show that variations in the RANTES gene affect RANTES protein production, hence altering host immunity. In this study, the relationship between presence of mutations in RANTES and incidence of malaria in a cohort of children living in a malaria-endemic area of Uganda was determined. Methods: This was a longitudinal study comprising of 423 children aged between 6 months and 9 years, who were actively followed up for 1 year. Malaria episodes occurring in the cohort children were detected and the affected children treated with national policy drug regimen. Mutations in the RANTES gene were determined by PCR-RFLP method and their frequencies were calculated. A multivariate negative binomial regression model was used to estimate the impact of RANTES mutations on malaria incidence. In all statistical tests, a P-value of <0.05 was considered as significant. Results: The frequencies of the -403A and In1.1C allele were 53.7 and 19.2 %, respectively. No mutations were found at the -28 locus. After adjustment of incidence rates for age, blood group, insecticide-treated bed net (ITN) use, malaria history and the sickle cell trait, 1n1.1T/C heterozygotes and homozygotes showed a non-significant trend towards higher incidence rates compared to wild-type individuals (IRR = 1.10; P = 0.55 and IRR = 1.25; P = 0.60, respectively). Similarly, there was no significant difference in malaria incidence rates between RANTES -403G/A heterozygotes or homozygotes and those without mutations (IRR = 1.09; P = 0.66 and IRR = 1.16; P = 0.50, respectively). No relation was seen between RANTES polymorphisms, baseline parasite densities and the time to first re-infection after administration of anti-malaria drugs. Conclusions: This study showed that the -403A mutation occurs in nearly half of the study population and the In1.1C allele occurs in one in every four children. Despite the high frequency of these mutations, there was no clear association with malaria incidence. Other studies evaluating more markers, that could potentially modulate RANTES gene transcription alongside other genetic modifiers of malaria susceptibility, may provide further explanations to these less dramatic findings.

  • 26.
    Lwanira, Catherine Nassozi
    et al.
    Makerere Univ, Coll Hlth Sci, Sch Biomed Sci, Kampala, Uganda..
    Kironde, Fred
    Islamic Univ Uganda IUIU, Fac Hlth Sci, Habib Med Sch, Kampala Campus, Uganda..
    Kaddumukasa, Mark
    Makerere Univ, Coll Hlth Sci, Sch Med, Kampala, Uganda..
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Prevalence of polymorphisms in glucose-6-phosphate dehydrogenase, sickle haemoglobin and nitric oxide synthase genes and their relationship with incidence of uncomplicated malaria in Iganga, Uganda2017In: Malaria Journal, ISSN 1475-2875, E-ISSN 1475-2875, Vol. 16, 322Article in journal (Refereed)
    Abstract [en]

    Background: Host genetics play an important role in Plasmodium falciparum malaria susceptibility. However, information on host genetic factors and their relationships with malaria in the vaccine trial site of Iganga, Uganda is limited. The main objective of this study was to determine the prevalence of selected host genetic markers and their relationship to malaria incidence in the vaccine trial site of Iganga, Uganda. In a 1-year longitudinal cohort study, 423 children aged below 9 years were recruited and their malaria episodes were investigated. Host genetic polymorphisms were assessed by PCR-RFLP, haemoglobin electrophoresis and DNA sequencing. Using a multivariate negative binomial regression model, estimates of the impact of human genetic polymorphisms on malaria incidence were performed. In all statistical tests, a P value of < 0.05 was considered as significant. Results: The prevalences of sickle cell haemoglobin trait, G6PD c. 202 G > A (rs 1050828) and NOS2 -954 G > C (rs 1800482) variants were 26.6, 22.7 and 17.3%, respectively. Inducible nitric oxide synthase 2 (NOS2 -954 G>C; rs 1800482) heterozygosity was associated with lower incidence of malaria in all age groups {Adjusted incident rates ratio (aIRR) 0.59; 95% CI [0.386-0.887]; P = 0.012)}. About 4% of study subjects had co-existence of sickle cell Hb trait and G6PD deficiency. Sickle cell Hb heterozygotes (Hb AS) aged less than 1 year experienced significantly more malaria episodes annually than children with normal haemoglobin (Hb AA) {aIRR = 1.98; 95% CI [1.240-3.175]; P = 0.004}. There was no significant influence of the sickle cell trait on malaria incidence among older children of 1-9 years. Conclusions: Mutation (NOS2 -954 G > C; rs 1800482) of nitric oxide synthase 2 gene promoter was associated with a lower incidence of acute malaria. The normal haemoglobin (wild genotype; HbAA) was associated with reduced malaria incidence rates during the first year of life. More understanding of the interplay between host genetics and malaria susceptibility is required.

  • 27. Marwa, Karol J.
    et al.
    Schmidt, Theresa
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Sjögren, Maria
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Minzi, Omary M. S.
    Kamugisha, Erasmus
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Cytochrome P450 single nucleotide polymorphisms in an indigenous Tanzanian population: a concern about the metabolism of artemisinin-based combinations2014In: Malaria Journal, ISSN 1475-2875, E-ISSN 1475-2875, Vol. 13, 420- p.Article in journal (Refereed)
    Abstract [en]

    Background: Artemisinin-based combinations currently recommended for treatment of uncomplicated Plasmodium falciparum malaria in many countries of sub-Saharan Africa are substrates of CYP enzymes. The cytochrome enzyme system is responsible for metabolism of about 80-90% of clinically used drugs. It is, therefore, important to obtain the pharmacogenetics of the population in the region with respect to these combinations and thereby enable practitioners to predict treatment outcomes. The aim of this study was to detect and determine allelic frequencies of CYP2C8*2, CYP2C8*3, CYP3A4*1B, CYP3A5*3 and CYP2B6*6 variant alleles in a Tanzanian indigenous population. Methods: Genomic DNA extraction from blood obtained from 256 participants who escorted patients at Karume Health Centre in Mwanza Tanzania, was carried out using the Gene JET (TM) Genomic DNA purification kit (Thermo Scientific). Genotyping for the cytochrome P450 variant alleles was performed using predesigned primers. Amplification was done by PCR while differentiation between alleles was done by restriction fragment length polymorphism (PCR-RFLP) (for CYP2C8*2, CYP2C8*3) and sequencing (for CYP2B6*6, CYP3A5*3 and CYP3A4*1B). Results: CYP2C8*2, CYP2C8*3, CYP3A5*3, CYP3A4*1B and CYP2B6*6 variant allelic frequencies were found to be 19,10,16,78 and 36% respectively. Conclusion: Prevalence of CYP2C8*2, CYP3A5*3, CYP3A4*1B and CYP2B6*6 mutations in a Tanzanian population/ subjects are common. The impact of these point mutations on the metabolism of anti-malarial drugs, particularly artemisinin-based combinations, and their potential drug-drug interactions (DDIs) needs to be further evaluated.

  • 28. Mongella, Stella
    et al.
    Enweji, Nizar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Mnongone, Naizihijwa
    Minde, Mercy
    Kamugisha, Erasmus
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    High prevalence of Plasmodium falciparum pfcrt K76T mutation in children with sickle cell disease at a tertiary hospital in north-western Tanzania2014In: Tanzania Journal of Health Research, ISSN 1821-6404, Vol. 16, no 4Article in journal (Refereed)
    Abstract [en]

    The high prevalence of sickle cell disease (SCD) and trait in Sub-Saharan Africa coincides with thedistribution of Plasmodium falciparum malaria. Due to prolonged heavy use of chloroquine (CQ) as anantimalarial, drug resistance has developed. Many countries including Tanzania abandoned the use of CQfor uncomplicated malaria, except its use as prophylaxis in patients with sickle cell disease. This studyinvestigated the prevalence of malaria in SCD patients and mutations associated with CQ resistance.Children diagnosed with sickle cell disease attending both outpatient clinic and those admitted at BugandoMedical Centre in north-western Tanzania were screened for malaria using thick blood smear. A driedblood spot on Whatman filter paper was also taken for polymerase chain reaction (PCR) and restrictionfragment length polymorphism. Among 123 known patients with sickle cell disease, the prevalence ofmalaria by blood smear microscopy was 3.2% and by PCR was 13.8%. The prevalence of K76T mutationamong the patients was 81.3%. The majority of the patients (72.4%) were using chloroquine prophylaxis. Inconclusion, the prevalence of malaria parasitaemia among children with sickle cell disease attending BMC islow (3.2%) by microscopy but several children maintain sub patent infection detectable by PCR. Theprevalence of chloroquine resistant P. falciparum in these children was higher than that previously seen innormal population in Tanzania. We recommend special attention to be paid to patients with sickle celldisease while studying the dynamics of drug resistant parasites.

  • 29.
    Qvarnström, Yvonne
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Jönsson, Maria
    Swedberg, Göte
    A method to study channelling of 6-hydroxymethyl-7,8-dihydropterin diphosphate in the folate biosynthesis pathwayManuscript (Other academic)
  • 30.
    Qvarnström, Yvonne
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Swedberg, Göte
    Additive effects of a two-amino-acid insertion and a single-amino-acid substitution in dihydropteroate synthase for the development of sulphonamide-resistant Neisseria meningitidis2000In: Microbiology, Vol. 146, 1151-1156 p.Article in journal (Refereed)
  • 31.
    Qvarnström, Yvonne
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Swedberg, Göte
    Sulphonamide resistant commensal Neisseria with alterations in the dihydropteroate synthase can be isolated from carriers not exposed to sulphonamides2002In: BMC Microbiology, Vol. 2, 34- p.Article in journal (Refereed)
  • 32.
    Qvarnström, Yvonne
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Swedberg, Göte
    Variations in gene organisation and DNA uptake sequence may limit transformational spread of sulphonamide resistance between commensal and pathogenic Neisseria speciesIn: Molecular Genetics and GenomicsArticle in journal (Refereed)
  • 33.
    Qvarnström, Yvonne
    et al.
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Swedberg, Göte
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Variations in gene organization and DNA uptake signal sequence in the folP region between commensal and pathogenic Neisseria species.2006In: BMC Microbiol, ISSN 1471-2180, Vol. 6, 11- p.Article in journal (Refereed)
  • 34. Rattanachuen, Woraphol
    et al.
    Jönsson, Maria
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Sirawaraporn, Worachart
    Probing the roles of non-homologous insertions in the N-terminal domain of Plasmodium falciparum hydroxymethylpterin pyrophosphokinase-dihydropteroate synthase2009In: Molecular and biochemical parasitology (Print), ISSN 0166-6851, E-ISSN 1872-9428, Vol. 168, no 2, 135-142 p.Article in journal (Refereed)
    Abstract [en]

    Plasmodium falciparum bifunctional hydroxymethylpterin pyrophosphokinase-dihydropteroate synthase (pfHPPK-DHPS) is a crucial enzyme in the de novo folate biosynthesis pathway. The crystal structure is not yet available for this enzyme, however, homology model of the enzyme reported previously revealed the presence of parasite-specific insertions. Alignment of pfHPPK-DHPS with HPPK and DHPS sequences from other microorganisms reveals two insertions relative to the corresponding enzyme in other organisms, i.e. HPPK-1 and HPPK-2. The former encompasses amino acid residues 66-162, while the latter covers residues 213-311. In order to investigate the roles of the two insertions, we constructed a number of mutants in which parts of these two insertions were deleted. Characterization of the mutationally altered proteins revealed that deletions of residues 74-80 in the HPPK-1 sequence of the pfHPPK-DHPS, but not that of the monofunctional pfHPPK, decreased the HPPK activity. A longer deletion (residues 74-86) in the HPPK-1 sequence of the bifunctional pfHPPK-DHPS completely inactivated both HPPK and DHPS activities. However, deletion in the HPPK-2 sequence from residues 247-306 did not disrupt the activities of HPPK and DHPS, but the kinetic properties of the recombinant proteins were slightly changed. The importance of HPPK-1 sequence on the catalytic activities of HPPK and DHPS in the bifunctional pfHPPK-DHPS could have implications for development of inhibitors targeting the non-catalytic region of this chemotherapeutically important enzyme.

  • 35. Sendagire, Hakim
    et al.
    Kaddumukasa, Mark
    Ndagire, Dorothy
    Aguttu, Clare
    Nassejje, Maureen
    Pettersson, Madeleine
    Swedberg, Gote
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Kironde, Fred
    Rapid increase in resistance of Plasmodium falciparum to chloroquine-Fansidar in Uganda and the potential of amodiaquine-Fansidar as a better alternative.2005In: Acta Trop, ISSN 0001-706X, Vol. 95, no 3, 172-82 p.Article in journal (Refereed)
  • 36. Sendagire, Hakim
    et al.
    Kyabayinze, Daniel
    Swedberg, Göte
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Kironde, Fred
    Plasmodium falciparum: higher incidence of molecular resistance markers for sulphadoxine than for pyrimethamine in Kasangati, Uganda.2005In: Trop Med Int Health, ISSN 1360-2276, Vol. 10, no 6, 537-43 p.Article in journal (Refereed)
  • 37.
    Sylvester, Boniphace
    et al.
    Muhimbili Univ Hlth & Allied Sci, Sch Publ Hlth & Social Sci, Dept Parasitol & Med Entomol, POB 65001, Dar Es Salaam, Tanzania..
    Gasarasi, Dinah B.
    Muhimbili Univ Hlth & Allied Sci, Sch Publ Hlth & Social Sci, Dept Parasitol & Med Entomol, POB 65001, Dar Es Salaam, Tanzania..
    Aboud, Said
    Muhimbili Univ Hlth & Allied Sci, Sch Med, Dept Microbiol & Immunol, POB 65001, Dar Es Salaam, Tanzania..
    Tarimo, Donath
    Muhimbili Univ Hlth & Allied Sci, Sch Publ Hlth & Social Sci, Dept Parasitol & Med Entomol, POB 65001, Dar Es Salaam, Tanzania..
    Massawe, Siriel
    Muhimbili Univ Hlth & Allied Sci, Sch Med, Dept Obstet & Gynaecol, POB 65001, Dar Es Salaam, Tanzania..
    Mpembeni, Rose
    Muhimbili Univ Hlth & Allied Sci, Sch Publ Hlth & Social Sci, Dept Community Med, POB 65001, Dar Es Salaam, Tanzania..
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Prenatal exposure to Plasmodium falciparum increases frequency and shortens time from birth to first clinical malaria episodes during the first two years of life: prospective birth cohort study2016In: Malaria Journal, ISSN 1475-2875, E-ISSN 1475-2875, Vol. 15, 379Article in journal (Refereed)
    Abstract [en]

    Background: Prenatal exposure to Plasmodium falciparum affects development of protective immunity and susceptibility to subsequent natural challenges with similar parasite antigens. However, the nature of these effects has not been fully elucidated. The aim of this study was to determine the effect of prenatal exposure to P. falciparum on susceptibility to natural malaria infection, with a focus on median time from birth to first clinical malaria episode and frequency of clinical malaria episodes in the first 2 years of life.

    Methods: A prospective birth cohort study was conducted in Rufiji district in Tanzania, between January 2013 and December 2015. Infants born to mothers with P. falciparum in the placenta at time of delivery were defined as exposed, and infants born to mothers without P. falciparum parasites in placenta were defined as unexposed. Placental infection was established by histological techniques. Out of 206 infants recruited, 41 were in utero exposed to P. falciparum and 165 infants were unexposed. All infants were monitored for onset of clinical malaria episodes in the first 2 years of life. The outcome measure was time from birth to first clinical malaria episode, defined by fever (>= 37 degrees C) and microscopically determined parasitaemia. Median time to first clinical malaria episode between exposed and unexposed infants was assessed using Kaplan-Meier survival analysis and comparison was done by log rank. Association of clinical malaria episodes with prenatal exposure to P. falciparum was assessed by multivariate binary logistic regression. Comparative analysis of mean number of clinical malaria episodes between exposed and unexposed infants was done using independent sample t test.

    Results: The effect of prenatal exposure to P. falciparum infection on clinical malaria episodes was statistically significant (Odds Ratio of 4.79, 95 % CI 2.21-10.38, p < 0.01) when compared to other confounding factors. Median time from birth to first clinical malaria episode for exposed and unexposed infants was 32 weeks (95 % CI 30.88-33.12) and 37 weeks (95 % CI 35.25-38.75), respectively, and the difference was statistically significant (p = 0.003). The mean number of clinical malaria episodes in exposed and unexposed infants was 0.51 and 0.30 episodes/infant, respectively, and the difference was statistically significant (p = 0.038).

    Conclusions: Prenatal exposure to P. falciparum shortens time from birth to first clinical malaria episode and increases frequency of clinical malaria episodes in the first 2 years of life.

  • 38. William, Buwembo
    et al.
    Rwenyonyi, Charles Mugisha
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Kironde, Fred
    Cotrimoxazole Prophylaxis Specifically Selects for Cotrimoxazole Resistance in Streptococcus mutans and Streptococcus sobrinus with Varied Polymorphisms in the Target Genes folA and folP2012In: International Journal of Microbiology, ISSN 1687-918X, E-ISSN 1687-9198, 916129- p.Article in journal (Refereed)
    Abstract [en]

    The selection of antibiotic resistance by cotrimoxazole prophylaxis was evaluated, and we characterized the mechanism of cotrimoxazole resistance in Streptococcus mutans and Streptococcus sobrinus. In vitro susceptibility to six antibiotics was evaluated on 64 mutans streptococci group (MSG) isolates from a cotrimoxazole prophylaxis group and compared to 84 MSG isolates from a nonprophylaxis group. The folA and folP genes were sequenced and compared with reference sequences at NCBI. Only resistance to cotrimoxazole was significantly higher in the prophylaxis group (54.7% versus 15.5%, OR = 6.59, 95% CI: 2.89-15.3, P < 0.05). Resistance to amoxicillin, ceftriaxone, chloramphenicol, erythromycin, and tetracycline was 1.4%, 25.5%, 6.2%, 6.5%, and 29.6% of the isolates, respectively. Considerable polymorphisms were found in the folP gene in S. mutans, but this could not be linked to sulfonamide drug resistance. No variation was seen in folP or folA genes of S. sobrinus. Genetic transfer of folate pathway genes seems unlikely in these isolates.

  • 39.
    Wilén, Maria
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Buwembo, William
    Sendagire, Hakim
    Kironde, Fred
    Swedberg, Göte
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Cotrimoxazole resistance of Streptococcus pneumoniae and commensal streptococci from Kampala, Uganda2009In: Scandinavian Journal of Infectious Diseases, ISSN 0036-5548, E-ISSN 1651-1980, Vol. 41, no 2, 113-121 p.Article in journal (Refereed)
    Abstract [en]

    Trimethoprim sulfamethoxazole (cotrimoxazole, CTX) is used frequently as part of standard medical care for people living with HIV/AIDS in Africa. The mechanisms of resistance to sulfonamides and trimethoprim in commensal streptococci from Uganda were determined and compared to S. pneumoniae. Commensal streptococci showing high-level resistance to cotrimoxazole were cultured and analysed for species identity and polymorphisms in the genes coding for dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR). Seven isolates of S. pneumoniae from blood and cerebrospinal fluid (CSF) were similarly examined. There was considerable polymorphism in both DHPS and DHFR. In DHFR, the mutations E20D and I100L were present in all sequenced isolates. Other mutations such as L135F, and different substitutions in D92, were frequent. The most common DHPS variants had 2 serine residues added after amino acid 60, or arginine and proline added after amino acid 59. In addition, 3 new insertions/substitutions were found. There were no obvious differences between the mutation patterns in S. pneumoniae and commensal streptococci, suggesting that the chromosomal mutations have been spread by transformational interchanges of DNA among related organisms.

1 - 39 of 39
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf