Mrinal K. Dasgupta

Biofilms and infection in dialysis patients.

Biofilm bacterial infections are implicated in most human bacterial infections and are also common in patients undergoing treatment with hemodialysis and peritoneal dialysis. Skin bacteria, which grow into microcolonies with biofilm formation in dialysis environments, are implicated in most of these infections. Dissemination of bacterial biofilms in hemodialysis patients induces bacteremia and endotoxemia. In peritoneal dialysis patients, biofilm causes peritonitis and catheter‐related infections with consequent loss of catheters and technique failure. Effective strategies for the diagnosis, intervention, and prevention of biofilm‐related infections in dialysis patients are described in this review.

A multicenter study of noncompliance with continuous ambulatory peritoneal dialysis exchanges in US and Canadian patients

Recent evidence suggested that noncompliance (NC) with continuous ambulatory peritoneal dialysis (CAPD) exchanges may be more common in US than in Canadian dialysis centers. This issue was investigated using a questionnaire-based method in 656 CAPD patients at 14 centers in the United States and Canada. NC was defined as missing more than one exchange per week or more than two exchanges per month. Patients were ensured of the confidentiality of their individual results. Mean patient age was 56 +/- 16 years, 52% were women, and 39% had diabetes. The overall admitted rate of NC was 13%, with a rate of 18% in the United States and 7% in Canada (P < 0.001). NC was more common in younger patients (P < 0.0001), those without diabetes (P < 0.001), and employed patients (P < 0.05). It was also more common in black and Hispanic than in Asian and white patients (P < 0.001). NC was more common in patients prescribed more than four exchanges daily (P < 0.0001) but was not affected by dwell volume. On multiple regression analysis, the independent predictors of NC, in order of importance, were being prescribed more than four exchanges per day, black race, being employed, younger age, and not having diabetes. Being treated in a US unit did not quite achieve significance as a multivariate independent predictor. These findings suggest that NC is not uncommon in CAPD patients and is more frequent in US than in Canadian patients. However, country of residence is less powerful as a predictor of NC than a variety of other demographic and prescription factors.

Myelin basic protein: a component of circulating immune complexes in multiple sclerosis.

Myelin basic protein (MBP) is an antigenic component of circulating immune complexes (CIC) in patients with multiple sclerosis (MS). Immune complexes were isolated from the sera by adsorption to Raji cells and then acid eluted. Final identification of MBP from Raji eluates was done by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by MBP radioimmunoassay (RIA) of gel eluates and by an immunoblot technique.

Circulating immune complexes in multiple sclerosis Relation with disease activity

Two hundred fifty-four MS patients were studied for circulating immune complexes (CIO by three different assays: Raji-RIA, Clq-PEG, and Conglutinin-BA. Thirty-five percent of the sera were positive by one or more of these tests; Raji-RIA had the highest sensitivity (29.4%). Incidence of CIC in acute relapse, progressive, remission, and stable state of MS was 33.3%, 30.2%, 26.1%, and 23.1%, respectively, by Raji-RIA, compared with 7.75% and 8.82% among normal and neurologic controls. The incidence of CIC in neurologic controls differed significantly from both acute relapse and progressive disease, and almost significantly from patients in remission. There was no significant difference between patients with stable MS and neurologic controls, and there was no association of CIC with HLA-B7.

Significance of Biofilm-Adherent Bacterial Microcolonies on Tenckhoff Catheters of CAPD Patients

The phenomenon of biofilm bacterial adherence to bioprosthetic devices and their relationship to various human infections are now well established. We have recently demonstrated that biofilm bacterial colonization of Tenckhoff catheters (TC) is very common in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) treatment. Based on our current work related to isolation of biofilm bacteria from peritoneal effluents of CAPD patients, we describe a novel way of diagnosis of this form of infection by using a modified Robbins device. Additionally, we describe the possible interaction of host defense factors with biofilm bacteria and ways to eliminate their colonization of TC for developing an overall strategy to prevent CAPD-associated peritonitis.

Combined evaluation of circulating immune complexes and antibodies toPseudomonas aeruginosa as an immunologic profile in relation to pulmonary function in cystic fibrosis

We developed a solid-phase radioimmunoassay with a reference standard pseudomonas antigen and used this with125I-labeled anti-human immunoglobulin to evaluate specific antibodies toPseudomonas aeruginosa, qualitatively and quantitatively, in sera from children with cystic fibrosis (CF) whose lungs were colonized by this bacterium. The results of this IgG assay correlated with the number of precipitin antibodies to the standard reference antigen determined by cross-immunoelectrophoresis in the same sera. Forced expiratory volume (FEV1; percentage predicted), determined as an indicator of lung injury in CF, was evaluated as an immunologic response to pseudomonas, against a profile derived from combined serial data on both the circulating immune complexes (CIC) and thePs. aeruginosa antibodies (N=25 CF patients; 108 sera). This revealed that in CF patients who had no specific IgG antibodies toPs. aeruginosa and no IgG-CIC had the best pulmonary function (FEV1=15±14.52%) and those with high levels of antibodies to this organism and high IgG-CIC levels had the poorest lung function (FEV1=69.75±10.99%) (P<0.05). We believe that this indicates an immunologic basis for lung injury in cystic fibrosis.

Three polyethylene glycol dependent methods for the detection of circulating immune complexes in pathological sera: Comparison with the Raji cell method

A composite method using polyethylene glycol (PEG) and different markers for detecting circulating immune complexes (CIC) is described. The markers used are bovine conglutinin (RK-BA), C1q (C1q-BA) and IgG, IgM quantitation of PEG precipitate (RID-Ig). A composite scoring system is used in interpreting results from individual assays. The sensitivity of multiple PEG methods (MPM) was determined in 418 serum samples and compared with Raji cell assay in 204. Correlations between individual assays, viz., RK-BA-C1q-BA, RID-Ig and Raji cell test in several disease conditions including rheumatoid arthritis, glomerulonephritis, post-renal transplantation, maintenance haemodialysis, multiple sclerosis and normal pregnancies were computed. The relative discriminatory ability of a single PEG technique to differentiate normal from pathological sera in these disease states was observed in comparison with the composite PEG index. This index gives an improved assessment of abnormal sera, is simple and sensitive and has some advantages over biological techniques such as the Raji cell assay.U

Exit‐site and catheter‐related infections in peritoneal dialysis: Problems and progress

Silastic peritoneal catheters are used routinely for peritoneal access in peritoneal dialysis (PD) because they are biocompatible. Catheter insertions are usually succeeded by bacterial adhesion and subsequent colonization of the catheter exit site. Despite the reduction in the proportion of peritonitis due to touch contamination, exit‐site and catheter‐related infections, particularly those caused by Staphylococcus aureus, remain the major cause of catheter loss and technique failure in PD. The peritonitis rate in the global PD population is steadily declining, but as the number of patients on PD increases by about 10% per year the stakes in infection control become greater, and one is forced to consider new options that will reduce the PD patient drop‐out rate. Three areas of promising advances in the prevention of exit‐site and catheter‐related infections are reviewed in this paper: (i) the use of prophylactic antibiotics to eliminate the nasal carriage of Staph. aureus and to reduce exit‐site infections; (ii) the Moncrief–Popovich catheter and implantation technique which reduces bacterial colonization of the catheter exit tunnel; (iii) new catheter implants composed in part of rigid biomaterials with antibacterial properties. This last category includes the silver‐coated silastic PD catheter, significant not only because it has great potential as a replacement for the silastic catheter, but also because it is a reminder that caution must be exercised before fully embracing new treatment options.

Antibody-mediated cellular cytotoxicity against Raji cells ADCC(Raji): evaluation of false positives in the detection of circulating immune complexes by Raji-cell assay.

Raji-cell radioimmunoassay is a very sensitive and reproducible method for the detection of circulating immune complexes. Using a complement-independent, antibody-dependent cellular cytotoxicity assay against51Cr-labeled Raji cells, there is no correlation between activity against Raji cells and positivity in Raji-cell radioimmunoassay for circulating immune complexes in three sets of sera (from renal transplantation patients, multiparous women, and patients suffering from systemic lupus erythematosus). We conclude that IgG antibodies to Raji membranes are not a significant cause of false-positive results in circulating immune complexes as detected by Raji-cell radioimmunoassay.

The absence of circulating immune complexes in patients with ankylosing spondylitis

SummarySera from 50 patients with well-defined ankylosing spondylitis were examined for circulating immune complexes using both a C1q binding (fluid phase) assay and a Raji cell assay. No more than five of the patients assessed had circulating immune complexes by either one of these techniques and none were positive in both. This result is in contrast to the high prevalence in sera from unselected patients with rheumatoid arthritis and systemic lupus used as positive controls.