Effects of Staphylococcus epidermidis on cellular immunity to infection with Listeria monocytogenes

With the present study, the effects of intravenous applications of Staphylococcus epidermidis (SE) on the course of experimental infections of mice with Listeria monocytogenes were evaluated. SE treatment 24 h prior to Listeria infection led to a reduced growth of Listeria organisms in both livers and spleens and to an increased resistance of infected animals against a lethal Listeria challenge. SE treatment 24 h after Listeria infection resulted in an enhanced growth of and retarded elimination of Listeria organisms from animal organs as well as in a reduction of delayed-type hypersensitivity to soluble Listeria antigen. Adoptive immunotherapy accomplished by transferring immune peritoneal exudate T-lymphocyte-enriched cells (PETLEs) to Listeria-infected recipients 24 h before SE treatment did not prevent the delay in clearance of Listeria organisms. When Listeria-infected recipients compromised in their immune response by SE treatment were infused with immune PETLEs either immediately or 24 h after the application of SE, the immunosuppression induced by SE proved to be reversible. It is concluded that, in analogy to other bacterial immunomodulators, Staphylococcus epidermidis is able to either nonspecifically activate macrophages or interfere with T-lymphocyte functions.