Staphylococcus aureus peritonitis is associated with Staphylococcus aureus nasal carriage in peritoneal dialysis patients

Although the definition of S. aureus nasal carriage in peritoneal dialysis patients is variable, carriage is often defined as 2 or more positive cultures for S. aureus. We investigated the relationship between S. aureus infections and nasal carriage (defined as 1 or more positive nose cultures) in 138 patients on peritoneal dialysis. By this definition, approximately 50% of the patients were carriers. The rates of S. aureus exit-site infection (0.28/year vs 0.43/year, p<0.001) and peritonitis (0.081/year vs 0.20/year, p<0.001) were lower in the noncarriers (patients with no positive nose cultures) than in those patients who had 1 or more positive nose cultures. Patients with only 1 positive nose culture had a similar S. aureus exit-site infection rate (0.31/year vs 0.28/year), but a higher peritonitis rate (0.24/year vs 0.08/year, p<0.001) compared to those patients with no positive nose cultures. However, patients with 2 or more positive nose cultures were at increased risk for both S. aureus exit-site infections and peritonitis. This relationship held even when only patients with frequent nose cultures were Included in the analysis. Thus patients with even 1 positive nose culture for S. aureus are at risk for S. aureus peritonitis and should not be classified as noncarriers.