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| 2. |
- Säll, Olof, 1980-
(författare)
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Infections in the central nervous system with focus on meningococcal disease : clinical and epidemiological aspects
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Infections in the central nervous system (CNS) include meningitis and encephalitis and are associated with high mortality and morbidity. A large number of different pathogens can cause these infections, including Neisseria meningitidis. It’s crucial to find the causative pathogen in order to provide the best treatment to the patient and for disease surveillance. In Paper I, molecular methods were used to investigate the microbial etiology in patients presenting with CNS infections at United Mission Hospital in Tansen, Nepal. Although the cerebrospinal fluid samples were analyzed for a large number of microbes using two commercial multiplex PCR panels and additional in-house real-time PCR, the etiology of the infections was still unknown in a large number of patients. This calls for further development of diagnostic methods for CNS infections.Neisseria meningitidis, the meningococcus, is a strictly human commensal but also capable to cause severe disease, typically in the form of sepsis and meningitis. The aim of Paper II and III was to study the clinical presentation of N. meningitidis serogroup Y and W infections, which increased unexpectedlyin Sweden from 2007 and 2014, respectively. By reviewing medical records of these infection episodes, the conclusion was drawn that atypical presentations with respiratory and gastrointestinal symptoms were common, rather than meningitis and petechiae.In Paper IV, meningococcal carriage was studied among students at Örebro University. Age ≤22 years, smoking, previous tonsillectomy, frequent partying and male gender were associated with higher carrier rates. The so far longest observation of carriage of the same meningococcal strain was presented, with a duration of at least one year.In conclusion, the results from these studies highlight the importance of early detection of meningococcal infections with atypical presentations and the need of improved diagnostics for CNS infections
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| 4. |
- Eriksson, Lorraine, 1990-, et al.
(författare)
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Difference in virulence between Neisseria meningitidis serogroups W and Y in transgenic mice
- 2020
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Ingår i: BMC Microbiology. - : BioMed Central. - 1471-2180. ; 20:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Neisseria meningitidis serogroups W and Y are the most common serogroups causing invasive meningococcal disease in Sweden. The majority of cases are caused by the serogroup W UK 2013 strain of clonal complex (cc) 11, and subtype 1 of the serogroup Y, YI strain of cc23. In this study, virulence factors of several lineages within cc11 and cc23 were investigated in transgenic BALB/c mice expressing human transferrin. Transgenic mice were infected intraperitoneally with serogroup W and Y isolates. Levels of bacteria and the proinflammatory cytokine CXCL1 were determined in blood collected 3 h and 24 h post-infection. Apoptosis was investigated in immune cells from peritoneal washes of infected mice. Adhesion and induction of apoptosis in human epithelial cells were also scored.RESULTS: The levels of bacteraemia, CXCL1, and apoptosis were higher in serogroup W infected mice than in serogroup Y infected mice. Serogroup W isolates also induced higher levels of apoptosis and adhesion in human epithelial cells. No significant differences were observed between different lineages within cc11 and cc23.CONCLUSIONS: N. meningitidis Serogroup W displayed a higher virulence in vivo in transgenic mice, compared to serogroup Y. This was reflected by higher bacteremia, proinflammatory activity, and ability to induce apoptosis in mouse immune cells and human epithelial cells.
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| 5. |
- Eriksson, Lorraine, 1990-
(författare)
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Exploring genomic and phenotypic differences in Neisseria meningitidis : understanding carriage and invasive disease
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Neisseria meningitidis can colonise the nasopharynx in humans and is also the cause of invasive meningococcal disease (IMD), which often presents as septicaemia and meningitis with high mortality rates. Invasive disease is often associated with specific capsular serogroups and clonal complexes (CC). In Sweden, serogroups Y and W have had a high incidence in recent years, but were previously considered rare causes of IMD, suggesting a change in the virulence potential of these serogroups. Currently, no specific genes exist that can reliably predict whether an N. meningitidis isolate will result in invasive disease or remain in the carriage state. Genetically similar isolates can be found during carriage and IMD, and it is more common for the carriage isolates to lack a capsule. The aim of this thesis was to investigate how genetic and phenotypic differences in N. meningitidis, can affect the virulence and the transition from a carriage state to invasive disease.The results indicate that the increase of serogroup W in Sweden is due to a specific lineage of CC11. This CC is rarely found among carriers and is considered highly virulent. Infections in transgenic mice with serogroup W CC11 isolates showed a greater virulence compared to serogroup Y isolates from other CCs. Although both serogroups are common causes of IMD in Sweden, they differ in virulence in transgenic mice. A genome-wide association study comparing carriage and invasive isolates, revealed that there were genetic variants in genes associated with virulence between these isolates. Among these variants were pilE/pilS, which are involved in the type IV pili. Comparison of pilE gene expression between carriage and invasive isolates showed no significant difference between these isolates. However, a difference in the class of the PilE protein was found between invasive and carriage isolates. Further research is needed to understand the impact of these genetic variations on the transition from carriage to invasive disease, also considering how factors in the human host and the environment that may contribute to the development of invasive disease.
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| 6. |
- Eriksson, Lorraine, 1990-, et al.
(författare)
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Genetic variants linked to the phenotypic outcome of invasive disease and carriage of Neisseria meningitidis
- 2023
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Ingår i: Microbial Genomics. - : Microbiology Society. - 2057-5858. ; 9:10
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Tidskriftsartikel (refereegranskat)abstract
- Neisseria meningitidis can be a human commensal in the upper respiratory tract but is also capable of causing invasive diseases such as meningococcal meningitis and septicaemia. No specific genetic markers have been detected to distinguish carriage from disease isolates. The aim here was to find genetic traits that could be linked to phenotypic outcomes associated with carriage versus invasive N. meningitidis disease through a bacterial genome-wide association study (GWAS). In this study, invasive N. meningitidis isolates collected in Sweden (n=103) and carriage isolates collected at Örebro University, Sweden (n=213) 2018-2019 were analysed. The GWAS analysis, treeWAS, was applied to single-nucleotide polymorphisms (SNPs), genes and k-mers. One gene and one non-synonymous SNP were associated with invasive disease and seven genes and one non-synonymous SNP were associated with carriage isolates. The gene associated with invasive disease encodes a phage transposase (NEIS1048), and the associated invasive SNP glmU S373C encodes the enzyme N-acetylglucosamine 1-phosphate (GlcNAC 1-P) uridyltransferase. Of the genes associated with carriage isolates, a gene variant of porB encoding PorB class 3, the genes pilE/pilS and tspB have known functions. The SNP associated with carriage was fkbp D33N, encoding a FK506-binding protein (FKBP). K-mers from PilS, tbpB and tspB were found to be associated with carriage, while k-mers from mtrD and tbpA were associated with invasiveness. In the genes fkbp, glmU, PilC and pilE, k-mers were found that were associated with both carriage and invasive isolates, indicating that specific variations within these genes could play a role in invasiveness. The data presented here highlight genetic traits that are significantly associated with invasive or carriage N. meningitidis across the species population. These traits could prove essential to our understanding of the pathogenicity of N. meningitidis and could help to identify future vaccine targets.
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| 8. |
- Hedberg, Sara Thulin, 1980-, et al.
(författare)
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Genetic characterisation of the emerging invasive Neisseria meningitidis serogroup Y in Sweden, 2000 to 2010
- 2011
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Ingår i: Eurosurveillance. - Saint-Maurice, France : European Centre for Disease Prevention and Control. - 1025-496X .- 1560-7917. ; 16:23
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Tidskriftsartikel (refereegranskat)abstract
- Neisseria meningitidis serogroups B and C have beenresponsible for the majority of invasive meningococcaldisease in Europe. Recently, an increase of N. meningitidisdisease due to serogroup Y has been notedin Sweden (in 2010, the proportion was 39%, with anincidence of 0.23 per 100,000 population), as well as inother northern European countries. We aimed to investigatethe clonal pattern of the emerging serogroup Yin Sweden during 2000 to 2010. The serogroup Y isolatesidentified during this time (n=85) were characterisedby multilocus sequence typing and sequencing ofthe fetA, fHbp, penA, porA and porB genes. The mostfrequent clone (comprising 28 isolates) with identicalallele combinations of the investigated genes, waspartly responsible for the observed increased numberof N. meningitidis serogroup Y isolates. It was sulfadiazineresistant, with genosubtype P1.5-2,10-1,36-2,sequence type 23, clonal complex 23, porB allele 3-36,fetA allele F4-1, fHbp allele 25 and penA allele 22. Thefirst case with disease due to this clone was identifiedin 2002: there was a further case in 2004, six during2006 to 2007, eight during 2008 to 2009, with a peakof 12 cases in 2010. An unusual increase of invasivedisease in young adults (aged 20–29 years) caused bythis clone was shown, but no increase in mortality ratewas observed.
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| 9. |
- Säll, Olof, 1980-, et al.
(författare)
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Atypical presentation of Neisseria meningitidis serogroup W disease is associated with the introduction of the 2013 strain
- 2021
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Ingår i: Epidemiology and Infection. - : Cambridge University Press. - 0950-2688 .- 1469-4409. ; 149
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Tidskriftsartikel (refereegranskat)abstract
- Since 2015, the incidence of invasive meningococcal disease (IMD) caused by serogroup W (MenW) has increased in Sweden, due to the introduction of the 2013 strain belonging to clonal complex 11. The aim of this study was to describe the clinical presentation of MenW infections, in particular the 2013 strain, including genetic associations. Medical records of confirmed MenW IMD cases in Sweden during the years 1995-2019 (n = 113) were retrospectively reviewed and the clinical data analysed according to strain. Of all MenW patients, bacteraemia without the focus of infection was seen in 44%, bacteraemic pneumonia in 26%, meningitis in 13% and epiglottitis in 8%, gastrointestinal symptoms in 48% and 4% presented with petechiae. Phylogenetic analysis was used for possible links between genetic relationship and clinical picture. The 2013 strain infections, particularly in one cluster, were associated with more severe disease compared with other MenW infections. The patients with 2013 strain infections (n = 68) were older (52 years vs. 25 years for other strains), presented more often with diarrhoea as an atypical presentation (P = 0.045) and were more frequently admitted for intensive care (P = 0.032). There is a risk that the atypical clinical presentation of MenW infections, with predominantly gastrointestinal or respiratory symptoms rather than neck stiffness or petechiae, may lead to delay in life-saving treatment.
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| 10. |
- Säll, Olof, 1980-, et al.
(författare)
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Etiology of Central Nervous System Infections in a Rural Area of Nepal Using Molecular Approaches
- 2019
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Ingår i: American Journal of Tropical Medicine and Hygiene. - : HighWire Press. - 0002-9637 .- 1476-1645. ; 101:1, s. 253-259
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Tidskriftsartikel (refereegranskat)abstract
- The etiology of infections of the central nervous system (CNS) in Nepal often remains unrecognized because of underdeveloped laboratory facilities. The aim of this study was to investigate the etiology of CNS infections in a rural area of Nepal using molecular methods. From November 2014 to February 2016, cerebrospinal fluid (CSF) was collected from 176 consecutive patients presenting at United Mission Hospital in Tansen, Nepal, with symptoms of possible CNS infection. After the CSF samples were stored and transported frozen, polymerase chain reaction (PCR) was performed in Sweden, targeting a total of 26 pathogens using the FilmArray® ME panel (BioFire, bioMerieux, Salt Lake City, UT), the MeningoFinder® 2SMART (PathoFinder, Maastricht, The Netherlands), and an in-house PCR test for dengue virus (DENV), Japanese encephalitis virus (JEV), and Nipah virus (NiV). The etiology could be determined in 23%. The bacteria detected were Haemophilus influenzae (n = 5), Streptococcus pneumoniae (n = 4), and Neisseria meningitidis (n = 1). The most common virus was enterovirus detected in eight samples, all during the monsoon season. Other viruses detected were cytomegalovirus (n = 6), varicella zoster virus (n = 5), Epstein-Barr virus (n = 3), herpes simplex virus (HSV) type 1 (HSV-1) (n = 3), HSV-2 (n = 3), human herpes virus (HHV) type 6 (HHV-6) (n = 3), and HHV-7 (n = 2). Cryptococcus neoformans/gatti was found in four samples. None of the samples were positive for DENV, JEV, or NiV. Of the patients, 67% had been exposed to antibiotics before lumbar puncture. In conclusion, the etiology could not be found in 77% of the samples, indicating that the commercial PCR panels used are not suitable in this setting. Future studies on the etiology of CNS infections in Nepal could include metagenomic techniques.
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