Acellular dermal matrix compared with synthetic implant material for repair of ventral hernia in the setting of peri-operative Staphylococcus aureus implant contamination: a rabbit model.

Background: Implant infection is a common clinical complication of abdominal hernia repair. Our objectives were to determine if acellular dermal matrix (ADM) grafts resisted Staphylococcus aureus infection better (as measured by ability to reduce or clear bacterial counts) than synthetic (polytetrafluoroethylene [PTFE]) mesh when used in abdominal wall reconstruction, and to determine whether vascularization of the implant occurred. We hypothesized that the ability of the ADM grafts to vascularize and allow cellular ingrowth would allow the immune system to clear the infection better in these animals.

Methods: In New Zealand White rabbits (average weight, 3.0 kg), a full-thickness 3 x 3 cm(2) abdominal defect was created, then repaired with an interpositional implant (ADM, n = 62; PTFE, n = 57). Before skin closure, the epidermal surface of each implant was inoculated with 1 mL of S. aureus at various concentrations (10(4) colony-forming units [CFU]/mL, n = 82; 10(6) CFU/mL, n = 27; 10(9) CFU/mL, n = 10), and the rabbits were harvested at either day 7 or day 21.

Results: At day 7, ADM grafts inoculated with 10(4) CFU had lower counts or no bacteria (p = 0.006), fewer adhesions (p = 0.005), and fewer abscesses (p = 0.008) than PTFE grafts. By day 21, more ADM (n = 12) than PTFE (n = 0) grafts were free of bacteria (p = 0.002). Fewer rabbits with ADM grafts formed abscesses (13 vs. 19; p = 0.03). When evaluating the 7- and 21-day 10(4) CFU groups combined, a total of 15 rabbits with ADM cleared the bacteria completely vs. none of those with PTFE grafts (p < 0.001). There was no significant difference in bacterial counts or wound complications at days 7 or 21 between PTFE and ADM implants when inoculated with 10(6) CFU. All rabbits inoculated with 10(9) CFU died of sepsis within 48 h. Herniation did not occur in any of the animals.

Conclusions: Our study demonstrates that ADM resists surgical site infection caused by S. aureus in an animal model without compromising the ventral hernia repair. This ability of ADM grafts to perform well in the setting of infection is most likely attributable to their capacity to vascularize and aid clearance of bacteria.