An In Vitro Model to Investigate the Influence of Antibiotics on Bacterial Susceptibility to Surface Phagocytosis by Human Polymorphonuclear Leukocytes

Abstract

The importance of bacterial adherence followed by invasion has been recognized in infective endocarditis wherein the bacteria must first adhere to the cardiac valve before colonization and invasion can occur [21]. Specific adherence of Staphylococcus aureus as well as S. epidermidis to endothelial cells and to artificial valvular prostheses has been demonstrated [6]. Some insight into the mechanism of invasion has recently been gained from the finding that endothelial cells may ingest S. aureus [17]. Fibronectin too has been shown to potentiate endothelial adherence but not phagocytic ingestion [8]. Likewise S. epidermidis is a common and innocuous inhabitant of human skin which can become an opportunistic pathogen of transiently or permanently implanted plastic prostheses such as intravascular catheters [18], CSF shunts [22], peritoneal dialysis catheters [24], orthopaedic devices [26], cardiac pacemakers [15] and prosthetic valves [23]. S. epidermidis is able to adhere to and to grow on the surfaces of such prostheses in vitro [2]. Later an extracellular slime substance is produced in which the staphylococci become enmeshed [19]. It has been suggested that this extracellular slime substance may also act as a virulence determinant in foreign body infections by interfering with some of the host defences [7] such as the lymphoproliferative response of mononuclear cells to polyclonal stimuli.

Part of this study was supported by Upjohn Inc., Kalamazoo, USA