BACKGROUND: Rifampin-soaked synthetic prosthetic grafts have been widely used for prevention or treatment of vascular graft infections (VGIs). This in vitro study investigated the effect of the antibiotics daptomycin and vancomycin and the new recombinant bacteriophage endolysin HY-133 on vascular cells, as potential alternatives compared to rifampin.

MATERIAL AND METHODS: Primary human ECs, vascular smooth muscle cells (vSMC), and fibroblasts were cultivated in 96-well plates and incubated with rifampin, daptomycin, vancomycin, and endolysin HY-133 for 24 h. Subsequently, after washing, cell viability was determined by measuring mitochondrial ATP concentration. Antibiotics were used in their corresponding minimum and maximum serum concentrations, in decimal multiples and in maximum soaking concentration. The experiments were performed in triplicate.

RESULTS: The 10-fold max serum concentrations of rifampin, daptomycin, and vancomycin did not influence viability of EC and vSMC (100 µg/ml, p>0.170). Higher concentrations of rifampin (>1 mg/ml) significantly (p<0.001) reduced cell viability of all cell types. For the other antibiotics, high concentrations (close to maximum soaking concentration) were most cytotoxic for EC and vSMC and fibroblasts (p<0.001). Endolysin did not display any cytotoxicity towards vascular cells.

CONCLUSIONS: Results of this in vitro study show the high cytotoxicity of rifampin against vascular cells, and may re-initiate the discussion about the benefit of prophylactic pre-soaking in high concentrations of rifampin. Further studies are necessary to determine the influence of rifampin on the restoration of vessel functionality versus its prophylactic effect against VGIs. Future use of recombinant phage endolysins for alternative prophylactic strategies needs further investigations.

Keywords: Bacterial Infections, endothelial cells, Myocytes, Smooth Muscle, Rifampin, Vascular Grafting