Peritoneal dialysis inevitability results in activation of inflammatory processes and its efficiency is highly variable between patients. An improved method to isolate biomarkers and study pathophysiological mechanisms in peritoneal dialysis effluent (PDE) is expected to be of much benefit for the development of this treatment approach and help with patient management. Extracellular vesicles (EVs) are released as part of normal cellular processes. Their proteome is expected to reflect both type and health of their cell of origin. Although there is a significant interest in using EVs for “liquid biopsies”, little is reported of their presence or composition in plentiful dialysis waste fluids, including peritoneal dialysis effluent (PDE). Here we determined the presence of EVs in PDE and subsequently characterized their proteome. EVs were first isolated from PDE using differential centrifugation, then a further enrichment using size exclusion chromatography (SEC) was performed. The presence of EVs was demonstrated using transmission electron microscopy, and their particle counts were investigated using nanoparticle tracking analysis and dynamic light scattering. Using tandem mass spectrometry, marker proteins from three types of EVs i.e. apoptotic bodies, ectosomes, and exosomes were identified. The proteomic results demonstrated that the isolation of EVs by differential centrifugation helped enrich for over 2,000 proteins normally masked by abundant proteins in PDE such as albumin and SEC markedly further improved the isolation of low abundant proteins. Gene ontology analysis of all identified proteins showed the marked enrichment of exosome and membrane-associated proteins. Over 3,700 proteins were identified in total, including many proteins with known roles in peritoneal pathophysiology. This study demonstrated the prominence of EVs in PDE and their potential value as a source of biomarkers for peritoneal dialysis patients.

No abstract

Catheter-related peritonitis is common but rarely caused by fungal infection. We report the first case of PD patients with catheter-related peritonitis form Aureobasidium pullulans , a black yeast-like dematiaceous fungus, and reviewing the relevant literatures. A potential cause of this infection is poor hand hygiene and improper fingernail care. The infection could be prevented if patient and caregiver strictly follow hand-washing protocols.

BackgroundGalactomannan index (GMI) at a level higher than 0.5 provides high sensitivity and specificity for the diagnosis of fungal peritonitis. Here, we report the false-positive of GMI in peritoneal dialysis (PD) effluent (PDE) due to Rhodococcus peritonitis in PD patients.Case presentationGMI in PDE of case #1 and case #2 were 1.53 and 0.76, respectively, while serum GMI of both cases was less than 0.5. In addition, GMI from the specimens obtained directly from the stationary phase of Rhodococcus colonies were 1.27 and 1.56, which were isolated from case #1 and #2, accordingly.ConclusionHigh GMI in PDE of PD patients is not specific just for fungal infections but may also be secondary to other infections, such as Rhodococcus spp., especially in endemic areas.

An additional yield of culture from the removed peritoneal dialysis (PD) catheter in diagnosis of pathogen causing refractory peritonitis was assessed in 118 eligible patients from 7 PD centers. Peritoneal dialysis fluid (PDF) culture identified organisms in 86 (72.9%) patients, while the catheter culture identified organisms in 55 (46.6%) patients. PD catheter culture could additionally identify organisms in 19 patients whose PDF culture were negative, increasing the positive culture rate to 89%, in other word 16.1% reducing the culture-negative rate. PD catheter culture provided additional yield, especially in fungal and enterococcal infections.