Background: Vascular grafts are increasingly implanted due to an increasing prevalence of atherosclerosis and diabetes, and about 1-6% of vascular procedures are complicated by infection. Mortality attributable to prosthetic vascular graft infections (PVGI) is high. However, there are almost no data regarding best treatment options of such complicated infections. Most recommendations are based on expert opinion and not on clinical trials or cohort observational data analyses. Evaluating infectious and other complications after vascular surgery procedures are important, and additionally, such studies may offer insights for quality improvement and improved patient outcomes. With the first aim investigators will establish an infrastructure for studying PVGI in Zurich. Investigators will take advantage of the Swissvasc registry, a central registry which collects preoperative, operative and discharge data regarding the index vascular surgical interventions. They will create a prospective observational cohort database of all patients who receive a vascular graft (peripheral, aortic, vein) at the University hospital of Zurich (VASGRA Cohort A). Patients with a PVGI will be included in VASGRA Cohort B and followed up using a flow chart with a focus on the course of this infectious complication. Additionally, investigators will establish a biobank with the collection of tissue- and blood samples of patients with PVGI. With the second aim researchers will investigate different diagnostic, clinical and therapeutic research questions nested in the VASGRA Cohort. Firstly, they will address epidemiological questions, such as: determine the incidence and outcome of complications after vascular graft placement; determine risk factors, best treatment strategies and outcome of PVGI, and determine the influence of different antibiotic regimens on the outcome of PVGI due to different bacterial pathogens. Secondly, investigators will determine the accuracy of different imaging techniques (PET/CT and MRI) for the diagnosis of PVGI, and their individual role for the assessment of treatment response. Thirdly, investigators will evaluate the bacterial diversity of vascular wound infections using 16s r-Ribonucleic acid (RNA)amplification, and investigators will explore whether this bacterial diversity does predict disease progression. Here, investigators will also study the impact of negative pressure wound therapy (NPWT) on bacterial diversity in the treatment course of PVGI. Fourthly, investigators will look for cut-off levels of relevant blood leucocytes count, C-reactive protein and procalcitonin raising suspicion of a PVGI. Lastly, investigators will look at histopathological features of excised vascular grafts. Expected value of the project: Results from the proposed study are an important contribution to the field, based on the large sample size, longitudinal design and by unifying clinical and epidemiological science. The very well characterized patient groups and the close connection between vascular surgeons, infectious disease specialists, specialists in nuclear medicine and microbiologist will help to investigate PVGI in depths. Investigators hope to be able to develop guidelines regarding best diagnostic modalities and treatment options in case of vascular graft infections. In the future we plan to examine bacteria retrieved from the PVGI in the laboratory in detail. The recovered bacteria will be examined for antimicrobial susceptibility and their capability to form biofilms. Furthermore investigators will examine how bacterial recovery form explanted grafts could be optimized.

Inclusion criteria:

Control patients:

- Vascular graft surgery (peripheral, aortic, vein)

Case patients:

• Patients with previous primary implantation of an aortic or peripheral vascular implant and suspicion of PVGI
• Age >18 years
• Written informed consent

Exclusion criteria:

• Drug or alcohol abuse
• Involvement in a conflicting clinical trial (investigational drug)
• Inability to follow the procedures of the cohort, e.g. due to language problems, psychological disorders or dementia of the subject
• Known or suspected non-compliance

All patients with a vascular surgery at the University hospital will be included in the study.