Experimental colonization of a polyester vascular graft with Staphylococcus aureus: a quantitative and morphologic...

Area of Science:

• Vascular Surgery
• Infectious Diseases
• Biomaterials Science

Background:

• Polyester (Dacron) vascular grafts are widely used in surgical procedures.
• Bacterial colonization of vascular grafts, particularly by Staphylococcus aureus, poses a significant risk of infection.
• Understanding the timeline of graft colonization is crucial for developing effective prevention strategies.

Purpose of the Study:

• To investigate the temporal dynamics of Staphylococcus aureus colonization on Dacron vascular grafts in a canine model.
• To correlate graft colonization levels with graft healing and surface characteristics.
• To identify critical time windows for preventing hematogenous vascular graft infections.

Main Methods:

• Thoracoabdominal aortic bypass using Dacron grafts was performed in 25 dogs.
• Dogs were subjected to bacteremic challenge with Staphylococcus aureus at various intervals (2 hours to 6 months) post-implantation.
• Graft segments were analyzed for bacterial counts (CFU/cm²) and examined using scanning electron microscopy.

Main Results:

• Bacterial colonization of Dacron grafts varied significantly with graft function duration (p < 0.01).
• Graft colonization was highest at 2 hours (median 4416.5 CFU) and 8 days (median 1515 CFU), decreasing to 1 CFU at 6 months.
• Scanning electron microscopy revealed colonization was associated with fibrin deposits and unorganized thrombotic matrix, particularly on bare polyester filaments.

Conclusions:

• Vascular graft colonization by Staphylococcus aureus is most pronounced in the early weeks following implantation.
• Graft healing and the organization of the thrombotic matrix appear to influence bacterial entrapment.
• These findings suggest that preventative measures against hematogenous vascular graft infection should focus on the initial period after surgery.