Adherence of Staphylococcus aureus isolated in peritoneal dialysis-relatedexit-site infections to HEp-2 cells and silicone peritoneal catheter materials

Background. Peritoneal catheter exit-site infections cause a relevant morbi dity in peritoneal dialysis patients and are frequently caused by Staphyloc occus aureus. We tested the hypothesis that adherence of exit-site-derived S. aureus to epithelial cells and peritoneal catheter silicone tubes discri minates virulent and less virulent strains. Methods. The binding of isolated S. aurues to an epithelial cell line (HEp- 2) and to silicone tubes was analyzed using light-microscopy or radioactive labeling of bacteria. Results. Of 378 exit-site swabs, 99 (26%) were positive for microbial growt h. S. aureus was cultured in 25 of 99 positive swabs; three of 13 swabs tak en in exit-site infections grade 3 and 4 that had tested positive for S. au reus. Adherence of S. aureus from exit-site infections grade 2, 3 and 4 to Hep-2 cells did not differ from adherence of bacteria isolated from asympto matic or moderately inflamed catheter exit sites (grade 0-2). However, bind ing of S. aureus to silicone tubes was enhanced in grade 0/1 compared with grade 2-4 exit-site isolates. Conclusions. Staphylococcus aureus is an important pathogen in CAPD-related exit-site infection being isolated in about 6.6% of all exit-site swabs (a nd in 25% of all positive swabs). Silicone-adhesive strains may be of more clinical significance in peritoneal dialysis patients since adhesion to sil icone was increased in S. aln ew strains isolated in more severe exit-site infections.