Prevention of vascular graft infections after impregnation with pathogen-specific bacteriophages: an in vitro experimental model

The in vitro antibacterial effect of bacteriophages (BPH) as impregnation agents was tested for prevention of vascular graft infections. Pathogen-specific BPHs for S. epidermidis, S. aureus, P. aeruginosa and E. coli were tested. In each case 7 segments of prosthesis tissue sized 1 cm(2) were impregnated for each group (15 min), a further 7 segments were used as a positive control and 4 as a negative control and 5 segments were observed under scanning electron microscopy (SEM). After 24 h incubation (37A degrees C) segments were washed 3 times in 20 ml PBS. Viable adherent bacteria were released by sonification and the optical density (OD) of the bacterial solutions was measured. A total of 6 dilution steps of 1:10 of the solution was made and incubated for 24 h (37A degrees C) on agar plates. Colony formed units (CFU) after the 4(th) and 6(th) dilution were counted. Impregnation with BPHs against S. epidermidis and E. coli showed a statistically significant reduction of OD, CFU-4 and CFU-6. For S. aureus and P. aeruginosa, all parameters were comparable to the positive control group. The microbiological findings were confirmed by SEM bio-films. The pathogen-specific BPHs tested were effective in prevention of in vitro graft infections caused by S. epidermidis and E. coli but not by S. aureus and P. aeruginosa.