Continuous Ambulatory Peritoneal Dialysis Host Defenses and Staphyloccus aureus Role of Opsonins, Fibronectin, Fibrinogen, and Fibrin

INTRODUCTION Peritonitis occurring in continuous ambulatory peritoneal dialysis (CAPD) patients due to Staphylo(:or;cus .aureus is generally more severe than tl\at caused by its coagulase-negative rela­ tive, Staphylococcus epidermidis.(l) An increased incidence of recurrence and catheter removal suggest~, impa~~ clearance of this organism from .. the peritoneum by the host's defenses. Whe~~aS peri~~~!ll macrophages (PM0s) from CAPD patients are able to phagocytose and kill Staph. aureus,,~~·3) the dilution of opsonins by dialysate, and the formation of fibrin clots may reduce efficiencY;;' ~taphylococcus aureus bears variaqle amounts of ffotein A on its cell wall, which is recognize4: by fibronectin, a protein with opsonic activity.() In addition, the Staph. aureus cell wall expresses another protein, "clumping factor," which recognizes fibrinogen as its substrate and pi~motes bacterial clumping.(S) Secretion of coagulase will result in conver­ sion of the fib~gen to fibrin, allowing bacterial adherence and sequestration within fibrin clots, providing· further protection of the bacteria from the host defenses. }'he ai:rq~":of our study were to assess the action of different opsonins, including fi­ bronectin, on bacterial phagocytosis both by PM0s and blood neutrophils. The influence of bacterial clumping and sequestration within fibrin on :phagocytosis was also studied.