Treatment of bacteria-biofilm graft infection by in situ replacement in normal and immune-deficient states.
OBJECTIVE
Complications of grafts infected with coagulase-negative staphylococci can be eradicated by antibiotic administration, tissue debridement, and in situ graft replacement, but successful treatment may be diminished in a setting of altered immune function.


METHODS
In a canine model of an established aortic graft infection from Staphylococcus epidermidis, outcomes after in situ replacement were compared between normal dogs and animals made immune-deficient by administration of azathioprine (50 mg/day) and prednisone (10 mg/day). In situ replacement of an infected infrarenal aortic graft with either antibiotic-bonded (silver-ciprofloxacin: Ag-cipro) or conventional polytetrafluoroethylene (PTFE) grafts was performed in 17 control and 18 immune-deficient animals.


RESULTS
Four weeks after implantation of a Dacron graft colonized with a biofilm of S. epidermidis, all study animals demonstrated a bacterial biofilm infection with perigraft inflammation or abscess, and in immune-suppressed dogs the incidence of perianastomotic aortitis was increased (p < 0.05). Six weeks after in situ replacement both the Ag-cipro and conventional PTFE grafts were healed without signs of infection in controls, but anatomic evidence of persistent infection and increased S. epidermidis recovery was observed in immune-suppressed animals that underwent in situ replacement of a standard (five of seven) versus antibiotic-bonded (one of 11) PTFE graft (p < 0.006). Overall in situ replacement with an antibiotic-bonded graft yielded a lower frequency of S. epidermidis recovery (two of 19 Ag-cipro graft biofilm with positive culture results versus nine of 16 conventional graft biofilm with positive culture results; (p < 0.003).


CONCLUSIONS
This study supports the efficacy of in situ replacement for low-grade graft infections caused by S. epidermidis in normal hosts and demonstrates superiority of antibiotic-bonded grafts in immune-deficient hosts.
Bandyk
D F
DF
Department of Surgery, University of South Florida College of Medicine, Tampa.
Kinney
E V
EV
Riefsnyder
T I
TI
Kelly
H
H
Towne
J B
JB
D000818:Animals; D001011:Aorta; D001379:Azathioprine / Q000627:therapeutic use; D001807:Blood Vessel Prosthesis / Q000009:adverse effects*; D003102:Colloids / Q000009:adverse effects*; D004285:Dogs; D005260:Female; D016867:Immunocompromised Host; D015994:Incidence; D008954:Models, Biological; D009779:Occlusive Dressings; D011091:Polyesters / Q000009:adverse effects*; D011138:Polytetrafluoroethylene; D011241:Prednisone / Q000627:therapeutic use; D016459:Prosthesis-Related Infections / Q000453:epidemiology / Q000276:immunology / Q000382:microbiology* / Q000628:therapy*; D013203:Staphylococcal Infections / Q000276:immunology / Q000382:microbiology*; D013212:Staphylococcus epidermidis
D003102:Colloids; D011091:Polyesters; D011138:Polytetrafluoroethylene; D001379:Azathioprine; D011241:Prednisone