Biofilm causes decreased production of interferon-gamma

Interferon-gamma, a cytokine, is produced by lymphocytes when they are stimulated by cytokines from activated macrophages, and is essential for macrophage-mediated bactericidal operations. To investigate whether a strain of bacteria can activate macrophages and lymphocytes, the interferon-gamma levels may thus be measured. Current literature maintains that peritoneal dialysis patients with recurrent peritonitis have "unhealthy" macrophages and lymphocytes unable to produce interferon-gamma, but that the administration of interferon improves the rates of peritonitis. In an in vitro experiment, Staphylococcus epidermidis, in both its planktonic and biofilm forms, was added to a suspension of peritoneal dialysis effluents, macrophages, and healthy peripheral blood lymphocytes, which were incubated at 37 degrees C for 18 h and then centrifuged. Subsequent levels of interferon-gamma were measured in the supernatants. Three such experiments were done with peritoneal macrophages and dialysis effluents collected from each of the three different patients involved in the study. It was found that little or no interferon-gamma (0.42 +/- 0.17 U/mL) was produced when biofilm bacteria were tested, but significant amounts of interferon-gamma (9.25 +/- 4.63 U/mL) resulted in conjunction with the planktonic form of the same bacteria. To eliminate experimental errors, all conditions were left identical, appropriate control groups were added, and each of the three experiments was duplicated. These in vitro data therefore provide new insight in the role of biofilm in the pathogenesis of recurrent peritonitis in peritoneal dialysis patients. Further clinical studies are required.