Granulation tissue formation in experimental wounds inoculated with Staphylococcus aureus.

The effects of inoculated Staphylococcus aureus microorganisms on developing granulation tissue were studied in rats. Hollow cylindrical viscose cellulose sponges were implanted subcutaneously as an inductive matrix for the growth of granulation tissue. The control implants were injected immediately after implantation with 1 ml of physiological saline while the experimental implants were injected with a corresponding volume of saline solution containing live staphylococci in the following concentrations: 10(2), 10(3), 10(4) or 10(5) microorganisms per milliliter. Analyses of wound fluid and granulation tissue were carried out two weeks after implantation. Implants inoculated with 10(3) or more organisms reproducibly developed infection which delayed healing while implants inoculated with 10(2) bacteria showed no infection and were usually able to clear themselves from the organisms. In the latter implants the number of wound fluid monocytes and macrophages was markedly elevated and the mean amount of collagen hydroxyproline exceeded the control level by 55%. This demonstrates that wound healing can be accelerated to a certain extent by inoculation of live staphylococci. The acceleration concerns only such bacterial concentrations which are able to promote a local inflammatory response but which can be governed by wound defence mechanisms.