Patients with end-stage renal disease undergoing hemodialysis (HD) are burdened with extremely high mortality rates (15% per year) and during the early stage (≤120days) the mortality rate is even higher (27% per year). Cardiovascular complications and bloodstream infections (BSIs) account for the vast majority of deaths in HD patients. In Denmark, BSIs occur in 14% of HD patients per year and is most frequently caused by Staphylococcus aureus (44%). The most frequent infectious complication is endocarditis that has fatal outcomes in ≈50% of the cases. Overall, 10% of HD patients die within 30 days after a positive blood culture for S. aureus. This project aims to answer key questions regarding HD patients' decreased ability to fight S. aureus BSIs and in particular the potential exacerbating effect of HD. We hypothesize that HD patients' blood is significantly compromised by the process of HD, to an extend that lowers immunoactivity against S. aureus. Moreover, we hypothesize, that contact activation promotes the coagulability of blood thus promoting biofilm formation by S. aureus which increases the overall risk of BSI. We will test these hypotheses by collecting blood and analyzing the inflammation and coagulation status in plasma samples from participants before and after HD. We will compare the level of the inflammatory markers in plasma from participants undergoing HD (n=180) to the level in plasma samples from three control groups: healthy volunteers (n=120), participants with renal disease not in dialysis (n=60) and participants undergoing peritoneal dialysis (n=40).

Participants with chronic kidney disease undergoing hemodialysis Inclusion criteria

• Age >18 years
• Chronic kidney disease
• Hemodialysis

Exclusion criteria:

- Acute kidney disease

Participants with chronic kidney disease, not in dialysis Inclusion criteria

• Age >18 years
• Chronic kidney disease (eGFR from <15 to 44)

Exclusion criteria:

• Acute kidney disease
• Hemodialysis
• Peritoneal dialysis

Participants with chronic kidney disease undergoing peritoneal dialysis Inclusion criteria

• Age >18 years
• Chronic kidney disease
• Peritoneal dialysis

Exclusion criteria:

- Acute kidney disease

Healthy volunteers Inclusion criteria

• Age >18 years
• Blooddonors

Exclusion criteria:

- NA

Blood samples and clinical information is collected from 180 participants with chronic kidney disease undergoing hemodialysis, before and after dialysis. Their levels of components from the innate immune system in plasma are compared to the levels in plasma samples from three control groups: 60 participants with chronic kidney disease not in dialysis, 60 participants with chronic kidney disease undergoing peritoneal dialysis and 120 healthy volunteers.