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- Cajander, Sara, 1980-
(författare)
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Dynamics of Human Leukocyte Antigen-D Related expression in bacteremic sepsis
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Monocytic human leukocyte antigen-D related (mHLA-DR) expression determined by flow cytometry has been suggested as a biomarker of sepsisinduced immunosuppression.In order to facilitate use of HLA-DR in clinical practice, a quantitative real-time PCR technique measuring HLA-DR at the transcription level was developed and evalutated. Levels of HLA-DR mRNA correlated to mHLADR expression and were robustly measured, with high reproducibility, during the course of infection. Dynamics of mHLA-DR expression was studied during the first weeks of bloodstream infection (BSI) and was found to be dependent on the bacterial etiology of BSI. Moreover, mHLA-DR was shown to be inversely related to markers of inflammation. In patients with unfavourable outcome, sustained high C-reactive protein level and high neutrophil count were demonstrated along with low mHLA-DR expression and low lymphocyte count. This supports the theory of sustained inflammation in sepsis-induced immunosuppression. The association between mHLA-DR and bacterial etiology may be linked to the clinical trajectory via differences in ability to cause intractable infection. Staphylococcus aureus was the dominating etiology among cases with unfavourable outcome. With focus on patients with S. aureus BSI, those with complicated S. aureus BSI were found to have lower HLA-DR mRNA expression during the first week than those with uncomplicated S. aureus BSI. If these results can be confirmed in a larger cohort, HLA-DR measurement could possibly become an additional tool for early identification of patients who require further investigation to clear infectious foci and achieve source control.In conclusion, PCR-based measurement of HLA-DR is a promising method for measurements of the immune state in BSI, but needs further evaluation in the intensive care unit setting to define the predictive and prognostic value for deleterious immunosuppression. The etiology of infection should be taken into consideration in future studies of translational immunology in sepsis.
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- Rasmussen, Gunlög, 1973-
(författare)
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Staphylococcus aureus bacteremia, molecular epidemiology and host immune response
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Staphylococcus aureus is a major pathogen responsible for a considerable disease burden worldwide. It may cause a wide array of infections, from superficial skin infections to invasive bacteremia and complications such as infective endocarditis (IE) and osteomyelitis. This thesis aimed to investigate aspects of the molecular epidemiology of S. aureus and host immune response in relation to disease manifestation, severity, and over time during S. aureus bacteremia (SAB).Genotypic characteristics in isolates causing colonization, bacteremia, and bacteremia with IE were studied. The S. aureus population was genetically diverse and certain clones with their set of often lineage-specific virulence genes were associated with invasive disease. Characterization of the long-term molecular epidemiology of MSSA bacteremia showed an increased prevalence of CC5 and CC15, while CC8, CC25 and CC30 declined. Antibiotic resistance pattern was favorable and unaffected.Further, different aspects of host immune response were explored in patients with SAB during the acute phase of bacteremia. When investigating the NLRP3 inflammasome signaling, induced caspase-1 activity was found, with a great inter-individual variation between patients, and subsequent release of IL-18, indicating inflammasome activity. Finally, the dynamics of MHC class II related genes HLA-DRA and CD74 were analyzed as markers of immunosuppression. Patients with complicated SAB had significantly lower HLA-DRA expression than patients with uncomplicated bacteremia, demonstrating an association between complicated SAB and impaired immune function.In conclusion, the S. aureus genotype, as well as host factors reflected by inter-individual variations in inflammasome signaling and immune function, may all contribute to disease manifestation and outcome during SAB. An ability to measure the immune response early and continuously during the hospital stay and course of bacteremia could offer a way to tailor patient management and treatment in an individualized way.
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- Ziegler, Ingrid, 1976-
(författare)
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Quantitative detection of bacterial DNA in whole blood in bloodstream infection
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis aims to increase the knowledge on how quantitative PCR can be used in the diagnostics of bloodstream infections, with an emphasis on quantitative elements.In Papers I and II, we evaluated quantitative data from two commercial PCR tests for pathogen detection directly in blood, Magicplex Sepsis (I) and SeptiFast (II), from patients with suspected sepsis. We found that high quantification cycle (Cq) values, indicating low DNA loads, were associated with findings of pathogens with doubtful clinical relevance, whereas low Cq values, indicating high DNA loads, were correlated with sepsis and septic shock, as well as with positive blood culture results.In Paper III, we aimed to study the bacterial DNA load during Staphylococcus aureus bacteremia, in relation to different clinical factors. For this purpose, we developed a droplet digital PCR (ddPCR) for precise DNA quantification, targeting S. aureus specifically. We found that a high initial S. aureus DNA load was associated with laboratory markers for immune dysregulation as well as with sepsis, endocarditis, and mortality.In Paper IV, we aimed to develop a tool for repeated DNA quantification during bloodstream infection. For this purpose, we optimized a ddPCR, targeting the universal bacterial 16S rDNA, and performed a comparison with species-specific ddPCRs on spiked blood, and on clinical samples. The performance of the16S rDNA ddPCR was adequate, and we found that a high 16S rDNA load was associated with sepsis and mortality.In conclusion, our results indicate that the pathogen DNA load in blood plays an important role in the clinical picture in BSI. In future research on molecular BSI diagnostics, studies on DNA loads and clearance should be included.
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