Host defences in continuous ambulatory peritoneal dialysis and the genesis of peritonitis

T cells in the peritoneum

The peritoneal cavity is a fluid-packed area that houses most of the abdominal organs, including the omentum, a visceral adipose tissue with milky patches or groups of leukocytes organized in the same way to those observed in typical lymphoid tissues. A distinct population of leukocytes patrols the peritoneal cavity and travels in and out of the milky spots, facing antigens or pathogens in the peritoneal fluid and responding appropriately. T cells may play a crucial function in regulating adaptive immune responses to antigens in the peritoneal cavity to ensure tissue homeostasis and healing. When peritoneal homeostasis is interrupted by inflammation, infection, obesity, or tumor metastasis, the omentum's dedicated fibroblastic stromal cells and mesothelial cells control peritoneal leukocyte recruitment and activation in unique ways. T cells, which employ their T cell receptor to target specific antigens, are an important component of the acquired immune response since they are present in the peritoneal cavity. The peritoneum provides a different environment for T cells to respond to pathogens. This chapter outlines the anatomy relevant to T cell function and biology, such as antigen processing/presentation, T cell activation, and the many T cell subpopulations in the peritoneal cavity, as well as their role in cancer or other infection.

Acute in Vivotoxicity of Heat-Sterilized Glucose Peritoneal Dialysis Fluids to Rat Peritoneal Macrophages

Objective

To evaluate the in vivo effects of heat-sterilized peritoneal dialysis (PD) fluids on the respiratory burst response of rat peritoneal leukocytes.

Design

Rats were exposed to intraperitoneal injections of a laboratory-made PD fluid that was either heat-sterilized (HPD) or filtered (F-PD). Control groups of animals were given Hank's buffer (HBSS) or saline (NaCI). Leukocytes were harvested by intraperitoneal lavage at different times in different animals and analyzed with respect to cell numbers, differential counts, and production of superoxide (chemiluminescence) in response to opsonized zymosan. The chemiluminescence responses of the macrophage and the neutrophil populations, respectively, were obtained by curve-fitting techniques from the responses of the mixed populations.

Results

All fluids induced a recruitment of neutrophils, the PD fluids causing a cell number increase that was more transient than that caused by NaCI and HBSS. Macrophage numbers were only slightly influenced, but were generally higher after NaCI and HBSS injections than after PD fluid injections. The H-PD exposure induced a significant inhibition of the macrophage chemiluminescence response after 2 and 12 hours, compared with the exposure to F-PD. The neutrophil chemiluminescence response was not significantly affected.

Conclusion

The toxins produced by heat-sterilization of glucose-containing PD fluids inhibit in vivo the respiratory burst response of peritoneal macrophages.

Characteristics of Peripheral and Peritoneal White Blood Cells in Children with Chronic Renal Failure, Dialyzed or Not

Objective

To explore further the mechanisms leading to immune deficiency in chronic renal failure and the role of dialysis treatment in these mechanisms.

Design

Cross-sectional and longitudinal analysis.

Patients

We studied 39 children treated with peritoneal dialysis (PD), 23 children treated with hemodialysis (HD), 33 children not yet dialyzed [chronic renal failure (CRF)], and 27 healthy children. Peritoneal cells were also obtained from PD children for analysis.

Methods

White blood cells (WBCs) were isolated from blood and peritoneal dialysis effluent by centrifugation. The number of CD2+, CD4+, and CD8+T cells, B cells, and natural killer cells were measured by flow cytometry.

Results

The total peripheral blood lymphocyte count was lower in PD children (2.6 x 109/L), HD children (2.1 x 109/L), and CRF children (2.0 x 109/L) compared with healthy children (3.1 x 109/L, p < 0.05). The B lymphocyte count was also lower in PD children (0.34x109/L), HD children (0.22 x 109/L), and CRF children (0.33 x 109/L) compared with healthy children (0.52 x 109/L, p < 0.01). Numbers of CD4+T cells were not different, but numbers of CD8+T cells were lower in PD children (0.56 x 109/L), HD children (0.63 x 109/L), and CRF children (0.53 x 109/L) compared with healthy children (0.77 x 109/L, p < 0.05). The count of natural killer cells was lower in PD children (0.21 x 109/L), HD children (0.17 x 109/L), and CRF children (0.18 x 109/L) compared with healthy children (0.50 x 109/L, p < 0.0001). The CD4/CD8 ratio of lymphocytes in peritoneal effluent was 0.8 versus 1.9 in peripheral blood ( p < 0.001). The CD2/CD19 ratio was not different. The cell subsets remained stable during the first year of PD treatment. The CD2/CD19 ratio in peritoneal effluent was higher in children with a peritonitis incidence ≥ 1 per year.

Conclusions

The reduced numbers of B lymphocytes, CD8+T cells, and natural killer cells found in CRF children, dialyzed or not, may favor the frequent occurrence of infections.

T Lymphocytes: The “Cellular” Arm of Acquired Immunity in the Peritoneum

T cells are an important part of the acquired immune response and target specific antigen with their T cell receptor. The peritoneum is a special milieu within which T cells react. We describe briefly the anatomy important for T cell function. T cell biology including antigen presentation, T cell activation, and the different T cell subpopulations are reviewed. We also define innate and acquired immunity and describe the role of polymorphonuclear cells and peritoneal mesothelial cells in the regulation of leukocyte population recruitment during peritonitis. We focus particularly on peritoneal lymphocytes and compare them to the regular lymphocyte populations in the circulation. We illustrate the role of PMCs in antigen presentation and discuss the changes of CD4+ helper T cell subtypes (Th1 and Th2) during peritoneal dialysis. The role of CD8+ cytotoxic T lymphocytes and their possible destructive role for the peritoneal membrane modified by advanced glycation end products are discussed. Polymorphonuclear cells play an important role in the regulation of inflammation and immunity. We describe their possible role in supporting T cells and particularly for generating memory CD8+ T cells by secretion of interleukin-15, a potent T cell growth factor. Light is shed on γδ T cells, a special T cell population that is able to recognize antigens without the restriction of antigen presentation. We end our review with a description of regulatory T cells. This cell population is extremely important in preventing autoimmunity and in the regulation of acquired immunity.

Peritonitis Affects the Relationship Between Low-Density Lipoprotein Cholesterol and Cardiovascular Events in Peritoneal Dialysis Patients

BACKGROUND

In peritoneal dialysis (PD), the relationship among low-density lipoprotein cholesterol (LDL-C), peritonitis, and cardiovascular (CV) disease has not been clarified. This study was performed to explore their associations in a large PD cohort.

METHODS

This retrospective cohort study included incident patients who received PD catheter insertion in our centre. The primary outcome was the first CV event (nonfatal myocardial infarction, CV death, non-haemorrhagic stroke, or any arterial revascularization procedure). Secondary outcomes were the occurrence of peritonitis, CV mortality, and all-cause mortality.

RESULTS

This study included 1294 patients, whose mean age was 48.1 years. After adjustment for confounders in negative binomial regression models, lower LDL-C quartiles were independently associated with a higher risk of peritonitis, compared with the highest quartile. The multivariate competing risk model showed no significant association between baseline LDL-C and the first CV event in the overall population. However, stratified analysis showed that each 1 mmol/L increase in LDL-C was independently associated with a 21% (subdistribution hazard ratio: 1.21, 95% confidence interval: 1.06-1.39) increased risk of the first CV event among peritonitis-free patients, and with a 20% (subdistribution hazard ratio: 0.80, 95% confidence interval: 0.65-0.99) decreased risk among patients with peritonitis. Moderating-effect analysis showed that the presence of peritonitis significantly influenced the relationships between LDL-C and CV events (P < 0.001). Similar results were also observed in the relationship between LDL-C and mortality.

CONCLUSIONS

PD patients with lower baseline LDL-C had a higher risk of peritonitis. The effect of LDL-C on CV events and mortality was different by the presence of peritonitis events.

Effluent and serum protein N-glycosylation is associated with inflammation and peritoneal membrane transport characteristics in peritoneal dialysis patients

Mass spectrometric glycomics was used as an innovative approach to identify biomarkers in serum and dialysate samples from peritoneal dialysis (PD) patients. PD is a life-saving treatment worldwide applied in more than 100,000 patients suffering from chronic kidney disease. PD treatment uses the peritoneum as a natural membrane to exchange waste products from blood to a glucose-based solution. Daily exposure of the peritoneal membrane to these solutions may cause complications such as peritonitis, fibrosis and inflammation which, in the long term, lead to the failure of the treatment. It has been shown in the last years that protein N-glycosylation is related to inflammatory and fibrotic processes. Here, by using a recently developed MALDI-TOF-MS method with linkage-specific sialic acid derivatisation, we showed that alpha2,6-sialylation, especially in triantennary N-glycans from peritoneal effluents, is associated with critical clinical outcomes in a prospective cohort of 94 PD patients. Moreover, we found an association between the levels of presumably immunoglobulin-G-related glycans as well as galactosylation of diantennary glycans with PD-related complications such as peritonitis and loss of peritoneal mesothelial cell mass. The observed glycomic changes point to changes in protein abundance and protein-specific glycosylation, representing candidate functional biomarkers of PD and associated complications.

Mycobacterium avium complex-associated peritonitis with CAPD after unrelated bone marrow transplantation

Peritonitis remains an important complication of peritoneal dialysis and is mostly caused by aerobic enteric bacteria. Non-tuberculous mycobacteria (NTM)-associated peritonitis is an unusual but serious infection, requiring special culture techniques to avoid delay in diagnosis. We report the case of an 11-year-old girl with aplastic anemia on ambulatory peritoneal dialysis who had Mycobacterium avium complex-associated peritonitis after allogeneic hematopoietic stem cell transplantation (allo-HSCT). This case emphasizes that we should be constantly cautious about NTM infection in allo-HSCT recipients, especially when standard cultures are negative and the infection is refractory to empirical antibiotic therapy.

Drainage vs no drainage in secondary peritonitis with sepsis following complicated appendicitis in adults in the modern era of antibiotics

AIM

To compare the profile of postoperative outcome in secondary peritonitis with sepsis due to complicated appendicitis in two cohorts (drainage vs no-drainage) after appendicectomy in adults in the modern era of effective antibiotics.

METHODS

A retrospective review of all adult patients who were operated for secondary peritonitis with sepsis due to complicated appendicitis was carried out. Total of 209 patients were identified from May 2005 to April 2009 with operative findings of gangrenous or perforated appendix. The patients were divided into two cohorts, those where prophylactic drainage was established (n = 88) and those where no drain was used (n = 121). Abdominal drain was removed once the drainage ceased or decreased (< 10-20 mL/d in closed system of drainage or when once daily dressing was minimally soaked in open system). Broad spectrum antibiotics to cover the gut flora were started in both cohorts at diagnosis and were stopped once septic features resolved. Peritoneal fluid for aerobic culture and sensitivity were routinely obtained intra operatively; however antibiotic regimens were not changed unless patient failed to respond to the antibiotics based on the institutional protocol. The co-morbidities and their influence on primary end points were noted. Immunocompromised patients, appendicitis complicated by inflammatory bowel disorder and tumors were excluded from the study.

RESULTS

Disease stratification and other demographic features were comparable in both cohorts. There was zero mortality in drainage group while as one patient (0.82%) died in the non-drainage group. The median duration (in days) of hospital stay (6.5 vs 4); antibiotic use (5 vs 3.5); regular parental analgesic use (5 vs 3.5) and paralytic ileus (2.5 vs 2) was more common in the drainage group. Incidence of major wound infection in patients 14 (15.9%) vs 22 (18.18%) and residual intra-abdominal sepsis (inter loop collection/abscess) -7 (8%) vs 13 (10.74%) requiring secondary intervention was not significantly different in drainage and non-drainage cohorts respectively. One patient in the drainage cohort had faecal fistula (1.1%).

CONCLUSION

The complicated appendicitis in the modern era of antibiotics does not necessitate the use of prophylactic drain placement which at times may even prove counterproductive.

Update on the challenging role of biofilms in peritoneal dialysis

Biofilms are commonly associated with an increased risk of patient infection. In peritoneal dialysis (PD), catheter associated infection, especially peritonitis, remains a clinically relevant problem. Although the presence of a biofilm is recognized in relapsing, repeat, and catheter-related peritonitis, it remains poorly characterized. In this review, an update on the role of biofilms in PD infections is presented. The emerging concept that host cells and tissue associated biofilms, in addition to the biofilms on the catheters themselves, contribute to the recalcitrance of infections is discussed. Furthermore, the evidence of biofilms on PD catheters, their developmental stages, and the possible influence of the PD environment are reviewed. The focus is given to ex vivo and in vitro studies that contribute to the elucidation of the interplay between host, microbial, and dialysis factors. The key issues that are still to be answered and the challenges to clinical practice are discussed.

WAVE1 mediates suppression of phagocytosis by phospholipid-derived DAMPs

Clearance of invading pathogens is essential to preventing overwhelming inflammation and sepsis that are symptomatic of bacterial peritonitis. Macrophages participate in this innate immune response by engulfing and digesting pathogens, a process called phagocytosis. Oxidized phospholipids (OxPL) are danger-associated molecular patterns (DAMPs) generated in response to infection that can prevent the phagocytic clearance of bacteria. We investigated the mechanism underlying OxPL action in macrophages. Exposure to OxPL induced alterations in actin polymerization, resulting in spreading of peritoneal macrophages and diminished uptake of E. coli. Pharmacological and cell-based studies showed that an anchored pool of PKA mediates the effects of OxPL. Gene silencing approaches identified the A-kinase anchoring protein (AKAP) WAVE1 as an effector of OxPL action in vitro. Chimeric Wave1(-/-) mice survived significantly longer after infection with E. coli and OxPL treatment in vivo. Moreover, we found that endogenously generated OxPL in human peritoneal dialysis fluid from end-stage renal failure patients inhibited phagocytosis via WAVE1. Collectively, these data uncover an unanticipated role for WAVE1 as a critical modulator of the innate immune response to severe bacterial infections.

Bacteria on catheters in patients undergoing peritoneal dialysis

BACKGROUND

Peritonitis is the leading cause of morbidity for peritoneal dialysis (PD) patients, and microbial biofilms have previously been identified on catheters from infected patients. However, few studies of catheters from patients without clinical signs of infection have been undertaken. The aim of the present study was to investigate the extent to which bacteria are present on catheters from PD patients with no symptoms of infection.

METHODS

Microbiologic culturing under aerobic and anaerobic conditions and confocal laser scanning microscopy were used to determine the distribution of bacteria on PD catheters from 15 patients without clinical signs of infection and on catheters from 2 infected patients. The 16S rRNA gene sequencing technique was used to identify cultured bacteria.

RESULTS

Bacteria were detected on 12 of the 15 catheters from patients without signs of infection and on the 2 catheters from infected patients. Single-species and mixed-microbial communities containing up to 5 species were present on both the inside and the outside along the whole length of the colonized catheters. The bacterial species most commonly found were the skin commensals Staphylococcus epidermidis and Propionibacterium acnes, followed by S. warneri and S. lugdunensis. The strains of these micro-organisms, particularly those of S. epidermidis, varied in phenotype with respect to their tolerance of the major classes of antibiotics.

CONCLUSIONS

Bacteria were common on catheters from patients without symptoms of infection. Up to 4 different bacterial species were found in close association and may represent a risk factor for the future development of peritonitis in patients hosting such micro-organisms.

Dialysis-associated peritonitis in children

Peritonitis remains a frequent complication of peritoneal dialysis in children and is the most common reason for technique failure. The microbiology is characterized by a predominance of Gram-positive organisms, with fungi responsible for less than 5% of episodes. Data collected by the International Pediatric Peritonitis Registry have revealed a worldwide variation in the bacterial etiology of peritonitis, as well as in the rate of culture-negative peritonitis. Risk factors for infection include young age, the absence of prophylactic antibiotics at catheter placement, spiking of dialysis bags, and the presence of a catheter exit-site or tunnel infection. Clinical symptoms at presentation are somewhat organism specific and can be objectively assessed with a Disease Severity Score. Whereas recommendations for empiric antibiotic therapy in children have been published by the International Society of Peritoneal Dialysis, epidemiologic data and antibiotic susceptibility data suggest that it may be desirable to take the patient- and center-specific history of microorganisms and their sensitivity patterns into account when prescribing initial therapy. The vast majority of patients are treated successfully and continue peritoneal dialysis, with the poorest outcome noted in patients with peritonitis secondary to Gram-negative organisms or fungi and in those with a relapsing infection.

Receptor-interacting protein 2 is a marker for resolution of peritoneal dialysis-associated peritonitis

There are no predictive factors for peritoneal dialysis-associated peritonitis; however, its resolution correlates with a cell-mediated Th1 immune response. We tested the hypothesis that induction of receptor-interacting protein 2 (RIP2), an assumed kinase linked with Th1 responses, is a useful marker in this clinical setting. Basal RIP2 expression was measured in human immune cells and during dialysis-associated peritonitis. RIP2 increased with bacterial toxin cell activation and the temporal profile for this differed depending on immune cell involvement in the innate or adaptive phases of the response. Importantly, RIP2 expression increased in peritoneal immune cells during dialysis-associated peritonitis and this upregulation correlated with clinical outcome. An early induction in peritoneal CD14(+) cells correlated with rapid resolution, whereas minimal induction correlated with protracted infection and with catheter loss in 36% of patients. These latter patients had higher levels of MCP-1 consistent with a delayed transition from innate to adaptive immunity. Our study shows that upregulation of RIP2 is a useful marker to monitor dialysis-associated peritonitis and in predicting the clinical outcome of these infections.

Staphylococcus aureus induces caspase-independent cell death in human peritoneal mesothelial cells

Bacterial peritonitis remains a serious complication of peritoneal dialysis. Although Staphylococcus epidermidis is the most common pathogen involved, infections with Staphylococcus aureus lead to severe peritoneal damage and are often associated with a dramatic loss of mesothelial cells. Induction of cell death appears to be involved in peritoneal damage and mesothelial cell loss during bacterial infections. Using cultured human peritoneal mesothelial cells (HMCs), we investigated the ability of different S. epidermidis and S. aureus strains to damage the HMC monolayer and to trigger cell death. We show that only a subgroup of live S. aureus isolates, characterized by an invasive and alpha-hemolysin-producing phenotype, induces cell death. None of the tested S. epidermidis strains, which were not invasive or hemolytic, had a cytotoxic effect. After host cell invasion, S. aureus resided within phagocytic vacuoles, and HMCs were apparently able to degrade staphylococci. However, even after prolonged infection, a high percentage of S. aureus remained alive within HMCs and might be released after host cell death. Cell death induced by S. aureus was accompanied by apoptotic alterations, such as DNA fragmentation, but was independent of endogenous FasL and tumor necrosis factor-alpha death ligand expression. Moreover, caspases were not involved in S. aureus-induced mesothelial cell death. In conclusion, our data indicate that mesothelial cell death might represent a major mechanism of S. aureus-induced damage of the peritoneum during bacterial peritonitis.

Peritoneal T cell responses can be polarized toward Th1 or Th2 in children on chronic peritoneal dialysis

Peritoneal T cell responses can be polarized toward Th1 or Th2 in children on chronic peritoneal dialysis. Previous studies on the peritoneal immune system described the presence of activated T lymphocytes in peritoneal effluents from subjects on chronic peritoneal dialysis (CPD). Since Th1/Th2 polarized response can influence the outcome of specific infectious diseases, we investigated if activated Th1/Th2 cells can be detected in peritoneal effluents during peritoneal dialysis, in order to better understand the role of T cells in the mechanisms of peritoneal defense. We have studied 8 children (4 males, 4 females, mean age 5.8 +/- 5.7 years, range 0.3-13.4) on CPD. Peritoneal cells have been isolated from peritoneal effluents by centrifugation. Immunofluorescent staining of intracellular cytokines for flow cytometric analysis was used to detect the percentage of T cells producing either IFN-gamma (Th1) or IL-4 (Th2). In the initial study 3 months after CPD initiation, high percentages of IFN-gamma positive peritoneal T cells (38% and 63%) were detected in two subjects; this finding is consistent with a Th1 polarization of peritoneal T cells. In another subject, high percentages of IL-4 positive T cells (31%) were detected, suggesting a Th2 polarization of peritoneal T cell response. Small amounts of either Th1 or Th2 T cells (2-4%) were also detected in the other subjects. At the 1 year follow-up, Th1 polarization persisted in one subject (18% IFN-gamma positive peritoneal T cells), in another a shift from Th1 to Th2 was observed, and in the other subject a down regulation of both T cell subsets occurred. The finding that a predominance of T cells producing either IFN-gamma or IL-4 was found in 3 out of 8 children strongly suggests that peritoneal T cell responses can be polarized toward Th1 or Th2. The decrease of Th1 and/or Th2 polarized T cells in the peritoneum of 4 out of 6 subjects (after 1 year) suggests that CPD can play an immunosuppressive role on T cell peritoneal responses. Further studies are needed in order to define whether different T helper activation patterns are associated with a higher risk of peritoneal infection or of peritoneal damage.

Management of peritonitis in children receiving chronic peritoneal dialysis

Bacterial peritonitis is a major threat to long-term peritoneal membrane function in pediatric patients receiving chronic peritoneal dialysis (CPD). This review summarizes the demographics, risk factors, and current recommendations regarding diagnostic procedures, management, and prevention of peritonitis in children. Albeit decreasing in incidence, bacterial peritonitis remains a major cause of technique failure in children with endstage renal disease receiving CPD. The use of standardized diagnostic procedures, efficacious antibacterial treatment, and objective response criteria are crucial in improving the outcome of this complication. Current guidelines recommend combining a first- and third-generation cephalosporin for empiric therapy in uncomplicated cases. The initial use of a glycopeptide/third-generation cephalosporin combination should be restricted to patients with risk factors for severe disease, as defined by clinical presentation, young age (<2 years), and recent infection with a methicillin resistant micro-organism. Several risk factors for primary or relapsing peritonitis have been identified, some of which are amenable to preventive measures. These relate to catheter design and implantation technique, connection methodology, early catheter removal in refractory or relapsing peritonitis, and eradication of Staphylococcus aureus from the catheter exit site and/or nasal reservoirs in patients and their caregivers.

IgG and IgG subclasses deficiency in children undergoing continuous ambulatory peritoneal dialysis and its provocative factors

BACKGROUND

Low levels of serum IgG or IgG subclasses may be responsible for the defective peritoneal defense and for peritonitis attacks in continuous ambulatory peritoneal dialysis (CAPD) children. Malnutrition, peritoneal loss or frequent peritonitis may lead to IgG or IgG subclasses deficiency.

METHODS

Levels of IgG subclasses were determined in 12 children undergoing CAPD treatment. Radial immunodiffusion technique was used for determination. Patients were aged from 6 to 16 years (mean age 12.3 years) and had been on CAPD for 11-26 months (mean duration 19.4 months). We evaluated whether IgG and IgG subclasses deficiency are related to malnutrition, the peritonitis rate and the duration of CAPD using the SPSS program.

RESULTS

Serum total IgG levels were found to be low in eight out of 12 patients. Eight patients showed low levels of IgG1, four patients IgG2, one patient IgG3 and three patients IgG4. Total IgG values were found to be positively correlated to malnutrition status, peritonitis rate and duration of CAPD. The IgG2 values were found to be related to the duration of CAPD. The IgG4 values were found to be correlated to the peritonitis rates.

CONCLUSIONS

The IgG and IgG subclasses deficiency may develop in children while on CAPD treatment. Periodical determinations of either serum IgG or the subclasses may be useful in the follow-up of these patients.

Expression of adhesion molecules and fibronectin of activated peritoneal surface with lipopolysaccharide (LPS) analyzed with immuno SEM

To disclose cell-to-cell interaction associated with the defensive mechanism of the peritoneum, the peritoneum was stimulated with lipopolysaccharide (LPS) and analyzed three-dimensionally, ultrastructurally, and immunohistochemically with immunoSEM (scanning electron microscopy). The activated hepatic peritoneal surface demonstrated numerous microvilli with the adhesion molecules ICAM-1 and VCAM-1. They were restricted to villi and peaked at 1.5 microg/g body weight of LPS. Delicate strands appeared moderately and were interwoven among microvilli with increasing LPS. These strands did not express ICAM-1 or VCAM-1, but fibronectin. Leukocytes began to adhere to the peritoneal surface above die value of LPS (2.5 microg). These results suggest that the peritoneal surface gives a defensive sheet for cell-to-cell interaction through adhesion molecules and fibronectin.

Heat-killed microorganisms induce PAI-1 expression in human peritoneal mesothelial cells: role of interleukin-1alpha

Human peritoneal mesothelial cells (HMCs) have a critical role in maintaining the intraperitoneal balance between fibrinolysis and coagulation by expressing the fibrinolytic enzyme, tissue-type plasminogen activator (tPA), as well as a specific plasminogen activator inhibitor (type 1; PAI-1). During bacterial peritonitis, the balance between intraperitoneal generation and degradation of fibrin is disturbed. As a consequence, severe peritoneal damage occurs, which is one of the leading causes of patient dropout from continuous ambulatory peritoneal dialysis (CAPD) therapy. Cultured HMCs isolated from omental biopsy specimens were used to study the effect of heat-killed strains (2 x 10(8)/mL) of Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli on the synthesis of tPA and PAI-1. Conditioned media were obtained by incubating cells with the different bacterial strains. tPA and PAI-1 antigen concentrations were measured in the cell supernatants by enzyme-linked immunosorbent assay. Each of the three heat-killed microorganisms induced a time-dependent increase in PAI-1 synthesis. After a 48-hour incubation period, the strongest effect was seen in the presence of S aureus (3.5-fold versus control), followed by S epidermidis (2.5-fold versus control) and E coli (1.5-fold versus control). Under the same conditions, tPA antigen levels did not change after exposure to S aureus or E coli, whereas the addition of S epidermidis resulted in enhanced tPA antigen production (2-fold versus control). The increase in PAI-1 synthesis in the presence of the heat-killed microorganisms was preceded by similar changes in interleukin-1alpha (IL-1alpha) levels. Inhibiting the activity of IL-1alpha with a neutralizing antibody significantly reduced bacterial-induced PAI-1 production. Our results indicate that the fibrinolytic imbalance during bacterial peritonitis depends on the bacterial species. The increase in PAI-1 synthesis, not the decrease in the production of tPA, alters mesothelial fibrinolytic activity. Because the increase in PAI-1 expression is significantly quenched by blocking the activity of IL-1alpha, the mesothelial release of this cytokine is involved in bacterial-induced changes in the fibrinolytic system.

Immunoglobulins in chronic renal failure of childhood: effects of dialysis modalities

BACKGROUND

It is not clear whether low serum levels of IgG (subclasses), previously demonstrated in children on peritoneal dialysis (PD), are related to the PD procedure or to factors associated with chronic renal failure (CRF). The aim of our study was to analyze the effect of PD on serum and PD effluent (PDE) IgG and subclass levels in children with end-stage renal failure.

METHODS

We measured albumin, IgG, IgA, IgM, and IgG subclasses in serum and PDE from children on PD (N = 40) and compared the serum values with those of children treated with hemodialysis (HD, N = 23) or presenting with CRF but not yet dialyzed (CRF; N = 63), and with a group of healthy controls (HCs; N = 67). Sixteen PD children could be followed sequentially from before starting PD and eight during a peritonitis episode.

RESULTS

Forty percent of the PD children showed reduced serum IgG2 levels (P = 0.0003) compared with 35% in HD (P = 0.006), 33% in CRF (P = 0.001), and 9% in HC children. IgG1 deficiencies were observed in 25% of PD patients (P < 0.0001), 4% of HD (P = NS), 16% of CRF (P = 0.0005), and 0% of HC children. IgG3 and IgG4 deficiencies were observed less frequently. Peritoneal clearances were similar for total IgG, IgG1, IgG2, and IgG4, but were lower for IgG3 (P < 0.05). No relationships were found between clearances and age or duration of PD treatment. Total IgG (P = 0. 003) and IgG1 (P = 0.002) levels declined just after starting PD. Peritonitis was associated with temporarily increased peritoneal loss of Ig, while the serum concentrations were unaffected. No significant relationship was found between the peritonitis incidence and reduced IgG or subclasses. However, all children with two or more peritonitis episodes per year had a reduced Ig level.

CONCLUSIONS

Although the mean serum concentrations of immunoglobulins were normal in all studied groups, a deficiency of one or more IgG subclasses was present in all groups with renal failure, suggesting inhibition of their synthesis by the uremic state. Ig deficiencies were more frequently found in PD, likely caused by protein loss in PDE. A high peritonitis incidence was associated with reduced serum Ig levels.

Intermittent versus continuous intraperitoneal glycopeptide/ceftazidime treatment in children with peritoneal dialysis-associated peritonitis. The Mid-European Pediatric Peritoneal Dialysis Study Group (MEPPS)

Intermittent intraperitoneal antibiotic administration appears as a practical and economical therapeutic concept in continuous peritoneal dialysis (CPD)-related peritonitis, but the equivalence of this principle with standard continuous treatment awaits confirmation by prospective, randomized clinical trials. This study evaluates the efficacy, safety, and clinical acceptance of an initial combination treatment including a glycopeptide (vancomycin or teicoplanin) and ceftazidime, each applied either intermittently or continuously, in a cohort of pediatric patients with CPD-related peritonitis. Patients randomized for continuous treatment received an intraperitoneal loading dose of glycopeptide and ceftazidime followed by maintenance doses added to each dialysate bag. In the intermittent treatment groups, the glycopeptide was administered in two loading doses 7 d apart, and ceftazidime during one dialysis cycle per day. Initial treatment response was evaluated after 60 h by the change in a Disease Severity Score and by the clinical decision to continue initial treatment. Of 152 patients observed for a total of 234 patient years, 90 patients developed 195 episodes of peritonitis (including 27 relapses within 4 wk after end of treatment). Dialysate cultures were positive in 83% of the episodes. In gram-positive peritonitis (79% of culture-positive cases), the primary success (overall 95%) and relapse rates (21%) were not different between continuous and intermittent, or between vancomycin and teicoplanin treatment. Oversensitivity reactions occurred in three and ototoxicity in one vancomycin-treated patient, whereas no such side effects were observed with teicoplanin. Residual renal function declined during peritonitis episodes regardless of treatment modality. In gram-negative peritonitis (18% of cases), intermittent ceftazidime treatment was less successful than continuous treatment according to clinical judgment (3 of 11 versus 10 of 14, P < 0.05), but not when rated by Disease Severity Score (8 of 11 versus 12 of 14). In conclusion, intermittent and continuous intraperitoneal treatment of CPD-related peritonitis with glycopeptides and ceftazidime is equally efficacious and safe when measured by objective clinical criteria. This contrasts with a strong tendency of clinicians to move from intermittent to continuous treatment in severe peritonitis.

Effect of alternative peritoneal dialysis solutions on cell viability, apoptosis/necrosis and cytokine expression in human monocytes

BACKGROUND

Cellular function, cell viability and the cytokine network of human monocytes are influenced by the specific composition of peritoneal dialysis (PD) fluids. In an in vitro study using isolated human blood monocytes, we investigated the effect of peritoneal dialysates containing amino acids (Amino) or glucose polymer (Glu-poly) instead of glucose (Glu) as the osmotic agent, and bicarbonate (Bic) or PBS instead of lactate (Lac) as a buffer.

METHODS

The following parameters were studied: mitochondrial dehydrogenase activity (using the MTT assay), interleukin (IL)-6 and IL-8 release (ELISA) and cellular IL-6 mRNA expression after lipopolysaccharide (LPS) stimulation (using RT-PCR). FACS flow cytometry with annexin V and propidium iodide as markers and fluorescence microscopic methods were used to study the effects of the test fluids on cell necrosis and apoptosis.

RESULTS

Glu/Lac pH 5.5 and Glu-poly/PBS pH 7.4 both significantly reduced mitochondrial dehydrogenase activity by more than 50% after 60 minutes of incubation (30.5 +/- 7.6%, 42.5 +/- 6.5%, referred to RPMI 1640 as 100%). Amino/Bic and Glu/Bic were both superior (Mtt assay > 63%). The rate of necrotic cells after 15 minutes of incubation measured by FACS was mostly increased with Glu/Lac pH 5.5 (29.9 +/- 4.0%). The rate of apoptotic cells, however, was not significantly different between the test solutions. The concentration of IL-6 in the supernatant of stimulated monocytes was highest with Glu/Bic (1023 +/- 278 pg/ml) and Amino/Bic (776 +/- 296 pg/ml) an lowest with Glu/lac pH 5.5 (46 +/- 22 pg/ml) and Glu-poly/PBS (32 +/- 13 pg/ml). IL-8 release from stimulated monocytes showed a similar pattern. Glu-poly/PBS showed a suppressive effect on IL-6 mRNA expression (ratio IL-6/beta-Actin, 0.4 +/- 0.25 vs. RPMI 1.5 +/- 3.6).

CONCLUSIONS

Bicarbonate buffered solutions both with glucose or amino acids as osmotic agents were superior when regarding cell metabolism, viability and cytokine release, while lactate buffered solutions and Glu-poly/PBS showed some reduced biocompatibility pattern for monocytes in vitro.

Staphylococcus lugdunensis: report of a case of peritonitis and an easy-to-perform screening strategy

We report on a severe case of peritonitis due to Staphylococcus lugdunensis. The clinical course resembled an infection due to S. aureus more than one due to other coagulase-negative staphylococci. Therefore, we strongly recommend identification and propose an easy-to-perform procedure for screening of this pathogen.