Initial Inoculation Concentration Does Not Affect Final Bacterial Colonization of In vitro Vascular Conduits

Area of Science:

• Biomaterials Science
• Infectious Diseases
• Vascular Surgery

Background:

• Prosthetic graft infections pose significant risks despite advancements in peri-operative care.
• Current models for studying graft infections lack standardization in bacterial concentration.
• This study investigates the impact of bacterial inoculation concentration on vascular graft attachment.

Purpose of the Study:

• To evaluate the effect of varying bacterial concentrations on attachment to different vascular graft materials.
• To determine the optimal bacterial concentration for in vitro vascular graft infection models.

Main Methods:

• Static in vitro assay using polytetrafluoroethylene (PTFE), Dacron®, nitinol, cobalt chromium, and Viabahn® grafts.
• Testing Staphylococcus aureus and Pseudomonas aeruginosa at concentrations from 10^4 to 10^8 CFU/mL.
• Quantifying bacterial attachment at 2 and 24 hours post-inoculation.

Main Results:

• Initial bacterial attachment percentage was low, increasing with higher inoculation concentrations but peaking at 14.8% for 10^8 CFU/mL.
• Pseudomonas aeruginosa showed the highest mean attachment across all materials and concentrations.
• Attachment order was consistent: Dacron ≈ PTFE < cobalt < nitinol < Viabahn.

Conclusions:

• Initial bacterial attachment to vascular grafts is consistently poor, irrespective of inoculation concentration.
• Complete bacterial attachment is achieved by 24 hours, even with low initial concentrations.
• A concentration below 10^7 CFU/mL is recommended for vascular graft infection models to ensure sufficient bacterial attachment.