We have developed an extracorporeal system for investigating in vitro the biofilm-adherent bacterial microcolonies (BABM) that grow on Tenckhoff catheters (TC), to study peritonitis in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). A modified Robbins’ device, attached to sampling plugs with TC discs and connected to the dialysate via a peristaltic pump, is run for 24 h; scrapings from pairs of TC discs are processed for assessment of viable BABM, one of each pair for culture by routine microbiology techniques and the other for examination by scanning and transmission electron microscopy (EM). No colonization was noted with fresh dialysis solutions and spent dialysates from patients without clinical peritonits; but, when bacterial suspensions were added to aliquots of the same dialysates, BABM were noted on both culture and EM. In a study of 4 patients on CAPD treatment, who had clinically evident peritonitis, routine cultures of spent dialysate were positive in only 2, but BABM were found in cultures and EM preparations of disc scrapings in all 4 cases. We conclude from these preliminary findings that this extracorporeal system is reliable, and well suited for studying the role of BABM in CAPD-associated peritonitis in vitro.

To examine the relationship of the formation of biofilm (adherent bacterial microcolonies) to recurrent peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPO) we examined the surfaces of 25 recovered Tenckhoff (T) catheters by scanning electron microscopy (SEM) and microbiological examination of scrapings. Twelve catheters had been removed after successful transplantation; the patients had not been dialyzed for three months and had no evidence of peritonitis during that period (control group), and only seven had experienced peritonitis (I or 2 episodes) before transplantation. All 13 patients in the study group had experienced repeated episodes of peritonitis (range 3–13, average, 5.6). We detected no significant differences between the control and study groups with respect to the percentage of catheter-surface covered by biofilm, or the proportion of catheter segments whose scrapings yielded positive bacterial cultures. It is concluded that large areas of the T catheters of CAPO patients are colonized by bacterial biofilms but only active dialysis predisposes to recurrent peritonitis.

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We simulated touch contamination of peritoneal dialysis fluids perfused through an in vitro system with a modified Robbins’ device (MRD) and Y-connecting tubings, to study the pathogenesis of bacterial biofilm (BB) growth on Tenckhoff catheter (TC) discs. The spike ends of Y-connecting sets were dipped in a suspension of freshly cultured cells of Staphylococcus epidermidis (3X10⁸ cfu/ml), and connected to 2 litres of 0.5 % dianeal solution which was perfused through the MRD with plugs containing TC discs. Four simulated clinical exchanges were performed with or without prior flushing and/or bleach treatment of the Y sets. Control experiments were done with fresh Dianeal solution with no contamination, flushing, or bleach treatment. BB growth on the TC discs was examined by scanning electron microscopy (SEM) and transmission electron microscopy and quantitated by routine culture of scrapings from the discs. We noted that touch contamination of dialysis fluids via the spike ends of the connecting sets can generate dense BB growth on TC discs in this experimental system (62 ± 8% by SEM and 10.2 ± 8.3 X 10³ cfu/ml by culture). This growth of BB was significantly reduced by flushing the Y set with sterile Dianeal solution (24.3 ± 3% by SEM and 5.7 ± 3.5 X 10¹ cfu/ml by culture) and was absent by bleach treatment. We conclude that although bleach treatment of Y sets can prevent BB growth, the ‘flushing’ procedure alone can significantly reduce BB growth on TC from touch contamination of dialysate fluid.