The application of metagenomic next-generation sequencing for detection of pathogens from dialysis effluent in peritoneal dialysis-associated peritonitis .

BACKGROUND: Metagenomic next-generation sequencing (mNGS) can improve pathogen identification in infectious diseases. METHODS: A prospective parallel control study was undertaken to evaluate the clinical significance of mNGS in identifying pathogens in dialysis effluent of patients with peritoneal dialysis-associated peritonitis (peritonitis). Dialysis effluent specimens were detected both by peritoneal dialysis effluent culture and mNGS. The positive rates and coincidence rates of the two methods were compared. RESULTS: From April 2020 to March 2021, 30 patients presenting with peritonitis were enrolled in this study. The positive pathogen detection rate of mNGS was significantly higher than that of the traditional culture method (86.67% vs. 60.00%; p = 0.039). Fifteen specimens were positive for both of the methods, while 11 specimens were negative for culture but positive for mNGS. Three specimens were positive for culture but negative for mNGS; all of them were streptococcus mitis. One specimen was negative for both methods. The culture method detected one type of pathogen in all specimens; however, two or more types of pathogens were detected in eight specimens by mNGS. In addition to common pathogens, additional pathogens detected by mNGS included Coxiella burnetii, human herpesvirus type 5, human herpesvirus type 6B and Mortierella. CONCLUSION: The pathogen detection rate of mNGS in dialysis effluent of peritonitis patients was significantly higher than that of traditional culture. The mNGS is advantageous in diagnosing the pathogens that are difficult to be cultured. However, mNGS did not demonstrate sensitivity to streptococcus mitis. Results from this study show that mNGS, combined with traditional culture, has potential application for detecting pathogens in peritoneal dialysis patients with peritonitis.

Gd/Y Hydroxide Nanosheets as Highly Efficient T1/T2 MRI Contrast Agents.

To develop highly efficient T1/T2 magnetic resonance imaging (MRI) contrast agents (CAs), Gd/Y hydroxide nanosheets were synthesized by a simple exfoliation method from layer compounds using sodium polyacrylate (PAA) as a dispersant and stabilizer. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) results revealed the excellent performance of monolayer nanosheets with thicknesses of up to 1.5 nm. The MRI results of the T1 and T2 relaxation times showed that all of the Gd/Y hydroxide nanosheets have high longitudinal and transverse relaxivities (r1 and r2). In particular, the 10% Gd-LRH nanosheets exhibited excellent MRI performance (r1 = 103 mM-1 s-1, r2 = 372 mM-1 s-1), which is rarely reported. Based on the relationship between the structure of 10% Gd-LRH nanosheets and their MRI performances, and the highly efficient MRI of spaced Gd atoms in the nanosheets, a special model to explain the outstanding MRI performance of the 10% Gd-LRH nanosheets is suggested. The cytotoxicity assessment of the 10% Gd-LRH nanosheets, evaluated by CCK-8 assays on HeLa cells, indicated no significant cytotoxicity. This study presents a significant advancement in 2D nanomaterial MRI CA research, with Gd-doped nanosheets positioned as highly efficient T1/T2 MRI CA candidates.

Suspension precipitation: A simple sediment-collecting method for microbiological culturing in diagnosis of peritonitis
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BACKGROUND: Rapid and accurate microbiological detection is crucial for effective treatment of peritonitis patients with peritoneal dialysis (PD). Although centrifugation of dialysis effluents can increase the pathogen culture-positive rate, a lack of both centrifugation facilities and experienced staff has prevented its widespread implementation, particularly in basic-level hospitals in developing countries. Thus, we developed a simple peritoneal sediment-collecting method, suspension precipitation method, for microbiological diagnosis of peritonitis. MATERIALS AND METHODS: In the suspension precipitation method, drained effluent bags from individual patients were hung for 1 hour to allow the suspension to drip to the bottom layer of the bag for sediment collection. Sediments obtained by centrifugation from the same batch of dialysis effluent were used as positive controls. Both sediment sample types were then cultured in blood-culture bottles. Subsequent analysis of the pathogen-positive detection rate and species comparison between the two methods were undertaken. RESULTS: Among 90 PD patients, the pathogen positive-detection rate between methods was comparable, as demonstrated by 75 (83.33%) with the suspension precipitation method and 77 (85.56%) by the centrifugation method. Their positive pathogen species were also similar, and the concordance rate was 97.78%. CONCLUSION: The suspension precipitation method is a simple, convenient, and reliable peritoneal sediment-collecting method that is suitable for a wide array of uses, particularly in basic-level hospitals without centrifugation technology.