IMMUNOSUPPRESSION AUGMENTS GROWTH OF GRAFT-ADHERENT STAPHYLOCOCCUS-EPIDERMIDIS

Objective: To determine if systemic suppression of host defenses durin g graft implantation alters the initial adherence and subsequent growt h of Staphylococcus epidermidis on vascular prostheses. Design: Dacron grafts 1 cm(2) were implanted in the back subcutaneous tissue of Swis s-Webster mice (n = 247), followed by topical inoculation with 2 X 10( 7), 2 X 10(5), 2 X 10(3), or 2 X 10(1) colony-forming units of S epide rmidis. Half of the mice were immunosuppressed with cyclophosphamide ( 150 mg/kg intraperitoneally), to achieve a consistent, significant dec rease in the white blood cell count and major histocompatibility compl ex class II (Ia) expression. Control mice received an equal volume of saline solution. Graft bacterial biofilm concentrations were determine d at 1 day for adherence and within 2 weeks for bacterial growth, by u sing sonication and quantitative agar culture. Results: Immunosuppress ion did not significantly alter the initial adherence of bacteria to v ascular grafts. Immunosuppressed animals that were inoculated with 2 X 10(7) and 2 X 10(5) colony-forming units of S epidermidis had signifi cantly higher bacterial biofilm concentrations as compared with those in control animals. Graft infection persisted at 14 days in all animal s, with and without immunosuppression. Conclusions: Suppression of imm une function during graft implantation augmented growth of adherent ba cteria. The effect of short-term perioperative immunosuppression on la te-appearing S epidermidis graft infection needs further study.