Biofilms in peritoneal dialysis.

Microbial adhesions and biofilm bacterial growth have been implicated in serious infections associated with the use of bioprosthetic medical devices and indwelling catheters in humans. Biofilm bacterial growth also commonly occurs on peritoneal dialysis (PD) catheters from skin bacteria. Mature biofilms develop high antibiotic resistance and cause recurrent peritonitis and catheter loss in a subgroup of PD patients. That subgroup of patients can be identified by comparing the antibiotic sensitivities [minimum inhibitory concentrations (MICs)] of a biofilm culture and a routine microbiologic (planktonic) culture of the same PD effluent.

The effects of macrolide and quinolone antibiotics in methicillin-resistant Staphylococcus aureus biofilm growth.

Recent studies demonstrate that 14-membered macrolides increase permeability and destruction of Pseudomonas biofilms. The effect of a macrolide antibiotic, erythromycin, on methicillin-resistant Staphylococcus aureus (MRSA) biofilm on Silastic catheter materials in comparison with two different quinolone antibiotics, sparfloxacin (SPFX) and a new quinolone, SYN 1193, was examined. Two different MRSA strains were grown in biofilm, using Mueller-Hinton broth with and without the addition of 10% pooled normal human serum (PNHS), in a modified Robbins device, at 37 degrees C for 24, 48, and 72 hours. Two different clinical MRSA strains were used and minimum bactericidal concentration (MBC) were determined at the time intervals mentioned. Three different dosages of each antibiotic were tested: 5.0, 20.0, and 50.0 micrograms/mL. In addition, a constant dosage of SPFX and SYN 1193, in combination with varying dosages of erythromycin, was tested under similar experimental conditions. SYN 1193 demonstrated the highest MBC in comparison to SPFX; addition of PNHS did not alter the effect of SYN 1193. However, erythromycin alone and in combination with SPFX and SYN 1193 had no effect on MBC. We conclude that (1) macrolide antibiotic erythromycin has poor MRSA biofilm permeability and killing in comparison to SPFX and SYN 1193, and (2) SYN 1193 had the highest MBC to MRSA biofilm.

Interferon-gamma levels in peritoneal dialysis effluents: relation to peritonitis.

As peritoneal macrophages require Interferon-gamma (IFN-gamma) for bacterial lysis, IFN-gamma levels were measured in peritoneal dialysis effluents. (PDE) by a specific radioimmunoassay. High IFN-gamma levels were found in patients with peritonitis compared to low levels in patients without peritonitis (mean 9.73 +/- 2.63 SE U/ml, N = 39 vs. 0.25 +/- 0.04, N = 32). IFN-gamma levels varied among different bacteria: Staph. aureus (highest: 23.4 +/- 5.7, N = 14), Staph. epidermidis (lower: 3.2 +/- 0.8, N = 13), other gram-positive (1.06 +/- 0.32, N = 6), gram-negative bacteria (lowest: 0.57 +/- 0.30, N = 6). After treatment of peritonitis levels decreased. In corresponding blood and PDE samples, by comparing IFN-gamma levels in 10 peritoneal dialysis patients (5 with peritonitis, 5 without), levels were raised only in PDE of patients with peritonitis, implying local IFN-gamma production. Total lymphocytes, T, B and monocyte subsets in patients' plasma and PDE did not differ, except for a higher number of mononuclear cells in PDE of patients with peritonitis (P < 0.05). Further investigation of in vitro IFN-gamma production in PDE with peritoneal monocytes, syngeneic host lymphocytes, and bacteria showed that Staph. aureus induced the highest levels of IFN-gamma and E. coli the lowest, in experiments with T cell enriched host lymphocytic fractions. We conclude that Staph. aureus peritonitis induces high levels of IFN-gamma in PDE, possibly by a T cell dependent superantigen response.

Development of bacterial biofilms on silastic catheter materials in peritoneal dialysis fluid.

A modified Robbins' device was used to monitor the growth of bacteria associated with clinical peritonitis in peritoneal dialysis fluid. To simulate bacterial colonization and biofilm formation on peritoneal catheters, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli were allowed to adhere to silastic disks and were then grown in fresh or used dialysis fluid. Adherent bacteria formed microcolonies and biofilms on silastics within 4 to 24 hours. Our data showed that colonization of the silastic disks was related to the quantity of bacteria and there were significant differences between the growth of adherent bacteria in fresh and used dialysis fluid. Adherent S epidermidis and P aeruginosa grew better in dialysis fluids than adherent E coli. These results suggest that S epidermidis and P aeruginosa are more likely to colonize silastic catheters and to cause catheter-related peritonitis in peritoneal dialysis patients than E coli.

Catheter biofilms and recurrent CAPD peritonitis.

To study the significance of biofilm bacteria in CAPD peritonitis, in a preliminary study, we compared the growth of planktonic and biofilm bacteria by parallel cultures of the same PD effluent in 14 patients with CAPD-associated peritonitis. Planktonic bacteria were isolated by routine microbiologic culture techniques and biofilm bacteria by the use of a modified Robbins' device (MRD). Antibiotic sensitivity or MIC's of bacterial strains isolated by the two techniques were compared. This comparison of the IC identified a subgroup of patients who developed recurrent antibiotic resistant biofilm-induced peritonitis and their peritoneal catheters were subsequently removed.

Growth of bacterial biofilms on Tenckhoff catheter discs in vitro after simulated touch contamination of the Y-connecting set in continuous ambulatory peritoneal dialysis.

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 (3 X 10(8) 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 10(3) 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 10(1) 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.