Role of an Intraperitoneal Catheter Implant in the Pathogenesis of Experimental Staphylococcus epidermidis Peritoneal Infection in Renal Failure Mice

Abstract

The influence of a permanent peritoneal catheter implant on the response of renal failure and control mice to peritoneal inoculation with 10⁶ colony-forming units (CFU) Staphylococcus epidermidis was assessed 48 h after bacterial challenge. Two weeks after the surgical induction of renal failure or sham surgery, a segment of a peritoneal dialysis catheter was implanted entirely within the confines of the peritoneal cavity of mice. One month later peritoneal S. epidermidis inoculation was performed by transcutaneous injection through the abdominal wall either directly into the peritoneal cavity (i.p.) or via the catheter lumen (i.e.). Following i.p. inoculation, minimal bacterial growth was recovered from the peritoneal structures of all mice, including the peritoneal catheter. In contrast, following i.e. S. epidermidis challenge, the catheter site remained heavily colonized while peritoneal washings and parietal peritoneum again presented minimal bacterial recoveries. S. epidermidis recovery from the catheter site of renal failure mice was significantly greater than from the respective site of sham-operated controls. Scanning electron microscopy of catheter segments recovered from mice following i.e. inoculation revealed single cocci or microcolonies associated with the catheter surface and differential leukocyte counts of fluid aspirated from the catheter lumen revealed evidence of acute inflammation. Signs of inflammatory processes in peritoneal washings and peripheral blood, however, were not observed. These results are discussed in relation to S. epidermidis peritonitis and continuous ambulatory peritoneal dialysis.

A Murine Model of Phosphate Nephropathy

“…Another important difference to the model of El-Abbadi et al is the fact that our mice were not uremic and can thereby serve to study early changes in calcium and phosphorus metabolism in chronic kidney disease. Furthermore, we were able to evaluate the morphologic changes in the kidney due to high oral phosphate load, which is not possible in the renal ablation model of Gallimore et al 34 that is induced by sequential electrocoagulation of the right renal cortex and left nephrectomy. A limitation of our model is, in contrast to the typical histologic changes in humans with phosphate nephropathy, the lack of renal fibrosis in our db/db mice treated with the phosphorus-rich diet at the evaluated time point.…”

Kinetics of <i>Staphylococcus epidermidis </i>Clearance from the Peritoneal Catheter Site of Renal Failure Mice following Intracatheter Inoculation

“…Our previous studies have demonstrated that the peritoneal catheter implant was a preferred site for bac terial persistence up to 48 h after 106 CFU IC S. epider midis inoculation and that bacterial clearance was fur ther compromised in renal failure mice [3]. In the cur rent study, most mice had cleared this inoculum 1 month after challenge; however, a small proportion of renal failure mice continued to harbor bacteria at the catheter site.…”

“…The surgical preparation and characteristics of this mouse model have been previously described [3,4,8], Placement of the catheter segment entirely within the confines of the peritoneal cavity preserved the integrity of intraperitoneal structures, and the resulting animal preparation was not limited by spontaneous sepsis con sequent to a catheter exit site through the abdominal wall and skin [8], At the time of our assessments, 7-10 weeks after surgery, renal failure mice were azotemic and presented significant anemia compared to sham-oper ated controls. Consistent with clinical observations dur ing chronic infections, sham-operated mice that were sacrificed at weekly intervals following 108 CFU IC 5. epidermidis inoculation developed significant anemia compared to infection-free controls.…”

“…As previously described, custom-made segments of OreopoulosZellerman CAPD catheters (Accurate Surgical Instruments, Toron to, Ont., Canada) were implanted intraperitoneally in mice 2 weeks after nephrectomy or sham surgery [3]. Both open ends of the seg ment were bevelled, and the 1.2-cm length contained six regularly spaced perforations.…”

“…This investigation is one of a series in which the pathogenesis of 5. epidermidis perito nitis, a major complication of continuous ambulatory peritoneal dialysis (CAPD), was studied. We have pre viously demonstrated that chronic renal failure has an immunosuppressive influence on the response of mice to peritoneal S. epidermidis inoculation [1][2][3]. In mice bearing an intraperitoneal catheter implant, S. epider midis persisted at the catheter site 48 h after intraca theter (IC) inoculation, and bacterial recoveries were sig nificantly greater in renal failure mice compared to sham-operated controls [3], On the basis of these studies we have addressed two questions; (1) Is .…”