Enhanced antimicrobial efficacy by impregnation of vascular grafts with nanocolloidal silver

Abstract

Objective

This in vitro study aims to evaluate any additional antimicrobial efficacy by impregnating nanocolloidal silver on commercially available vascular grafts, to compare the results with precoated silver grafts, and to test the feasibility of the procedure.

Methods

Vascular grafts from a prosthetic graft material of polyester (polyethylene terephthalate, Dacron) and from a xenograft (bovine pericardium) were sprayed with a nanocolloidal silver solution on both sides of the grafts and left to vaporize for 10 minutes. Thereafter, the grafts were cut into 1 × 1 cm² graft units (GUs) and incubated at 37°C for 1 or 24 hours, respectively, with a 10⁶ bacteria/mL solution from four bacterial strains: Pseudomonas aeruginosa, Staphylococcus epidermidis, Escherichia coli, and methicillin-sensitive Staphylococcus aureus. In addition, the untreated grafts from polyester and bovine pericardium, as well as the precoated silver grafts, were cut and incubated analogously, resulting in 5 groups of 80 GUs each (n = 400). After incubation, each GU was washed and sonicated and samples from each sonication fluid were plated on separate Müller-Hinton Agar (MH) plates. These were incubated at 37°C and CFU were counted after 24 hours.

Results

Grafts impregnated with nanocolloidal silver spray demonstrated a statistically significant decrease in detected adhering bacteria compared to their controls, both after 1 hour and 24 hours of incubation (P_adj < .001 to .006). The only nonsignificant result was recorded for polyester after 1 hour of incubation with Pseudomonas aeruginosa (P_adj = .721). In addition, no significant difference between the impregnated grafts and the precoated silver graft was demonstrated after 24 hours of incubation.

Conclusions

Impregnating vascular grafts from polyester and bovine pericardium with a nanocolloidal silver spray, before inoculation with a bacterial suspension, significantly reduced bacterial colonization on the grafts. The procedure proved feasible and should be tested further in in vitro and in vivo trials.