Local instillation of Staphylococcus aureus peptidoglycan at operation prevents wound healing impairment after trauma

Considerable experimental evidence and limited clinical evidence indicate that wound healing is impaired after trauma. Because Staphylococcus aureus peptidoglycan (SaPG) accelerates healing in normal rats and prevents wound healing impairment induced by glucocorticoids, cyclophosphamide, and streptozotocin-diabetes, we hypothesized that SaPG would prevent the impaired wound healing after trauma.

In each of two experiments, 18 Sprague-Dawley male rats were divided into two groups, nine rats each, paired by weight; one group received unilateral comminuted femoral fracture and wounding (two dorsal skin incisions and six subcutaneous polyvinyl alcohol [PVA] sponges), and the other group was only wounded. The incision and PVA sponges on one side were inoculated at operation with saline (200 microL/incision, 50 microL/sponge) and on the other side with SaPG in saline (860 microg of SaPG per centimeter of incision, 0.5 mg of SaPG per sponge). Rats ate chow and drank tap water ad libitum and were killed 7 days postoperatively.

In both experiments, the wound breaking strength (WBS) of saline-inoculated incisions was significantly lower in rats with femoral fracture; histologically, reparative granulation tissue was looser and less prominent. WBS of SaPG-inoculated incisions in rats with and without femoral fracture was significantly higher than that of saline-inoculated incisions and, histologically, reparative tissue was more prevalent, more closely packed, and more mature. WBS of SaPG-inoculated incisions in rats with femoral fracture was similar to that of saline-inoculated incisions in rats without femoral fracture. Reparative tissue hydroxyproline and histologic findings of saline-inoculated PVA sponge reparative tissue were similar in all rats, as were the increases induced by SaPG inoculation.

Wound breaking strength and histologic findings of skin incisions (impaired in rats with unilateral femoral fracture) are more sensitive to the adverse effects of trauma than accumulation of PVA sponge reparative tissue. A single inoculation of SaPG at operation increased wound incision healing in rats both without and with femoral fracture and notably prevented the impaired healing in rats with femoral fracture.