Defining the Microbiological Quality of Dialysis Fluid

Abstract

With increasing awareness about the degree and the potential impact of microbiological contamination in dialysis fluids, there is a desire to improve their microbiological quality. To achieve this goal, the origin of the microbiological contamination has to be identified. The water, the bicarbonate concentrate, and the fluid distribution system can be major contributors. Regular disinfection of the entire fluid path is necessary to prevent the formation of biofilm. The bicarbonate concentrate should be handled with special attention because it constitutes an excellent growth medium for microflora that may not be detected with regular assays. With a well maintained reverse osmosis (RO) system, frequent disinfection of the entire flow path, and microbiological awareness, it is possible to produce dialysis fluid that meets the most stringent standard (<10(2) colony forming units (CFU)/ml and <0.25 IU/ml of endotoxin). Adding a step of ultrafiltration just before the dialyzer can make the dialysis fluid ultrapure (<10(-1) CFU/ ml and <0.03 IU/ml). One additional step of controlled ultrafiltration provides sterile and pyrogen-free fluids (<10(-6) CFU/ml and <0.03 IU/ml) that can be used for infusion.

Comparison of techniques for culture of dialysis water and fluid

“…One authority says that "the primary purpose of the assays is to determine the degree of magnitude of microbial contamination and not to precisely quantify or identify bacteria in these fluids." 22 Others say that "For a realistic viable count, the original conditions of the sample should be mimicked as much as possible", 15 and that "the aim is to reproduce the natural growth conditions for relevant strains as closely as possible." 23 Arduino and colleagues noted that "gramnegative organisms responsible for producing significant amounts of endotoxin will grow to be visible on a culture plate [TSA] within 24 to 48 h" and that "the ready availability of TSA in clinical and commercial laboratories makes this the medium of choice in the culturing of dialysis fluids."…”

“…12 Both approaches have microbiologic rationales: TGEA and R2A methods are performed at a temperature and nutrient level close to that of dialysis water and its resident microorganisms, and have been shown to yield higher colony counts in several studies. 10,[13][14][15][16] TSA-48h cultures are performed at the temperature at which the patient is exposed to dialysis fluid in the dialyzer. 17 In addition, TSA-48h has the operational advantage that results are available more quickly, allowing earlier corrective action, and allows a laboratory to operate more efficiently.…”

“…Most previous studies examining the use of various methods to culture water and dialysis fluid ( Table 1) 18 concluded that lower nutrient medium, lower incubation temperatures and longer incubation times, similar to those specifically recommended by the ISO standards, result in higher total counts and better recovery of pigmented Gram negative organisms than do methods using higher nutrient content, shorter incubation times and higher incubation temperatures, [13][14][15][16]19 similar to the methods recommended by AAMI RD52, 10 incorporated into the CMS 2008 ESRD CfC, 11 and used in the U.S. Although the current international standards cite these studies to justify their recommendations, the studies are small, use samples of little relevance to the dialysis environment (such as potable water), use reference points higher than 50 CFU/mL, and are inconsistent in incubation conditions and in the pairing of culture methods compared.…”

Purity and Stability of Online-Prepared Hemodiafiltration Fluid after Storage

“…The BacT/ALERT is a fully automated, dual temperature system, which may be used to conduct sterility testing at 35°C. The membranes of the filter (at T0 and for each day of storage) were placed in tryptone glucose extract agar plates (Agricons, Italy) and incubated at 22°C for 7 days [11,12,13]. Endotoxins from Gram-negative bacteria were detected and quantitated using the kinetic limulus amebocyte lysate endotoxin test (LAL Pyrotell® Single Test Vial, Associates of CAPECOD, East Falmouth, Mass., USA) [14,15].…”

Cardiovascular Disease in Dialysis Patients

“…Potential sources of endotoxaemia that are pertinent to the ESKD population include contaminated dialysate, dialysis catheters and circuitry (HD and PD), peritoneal membrane dysfunction, gastrointestinal bacterial translocation and periodontal disease [12,152]. Preventative strategies such as avoidance of temporary dialysis catheters and use of ultrapure water have been shown to reduce endotoxin levels [153,154]. Initial evaluation of gut flora modulation through use of pre-and probiotics [155] as well as gastrointestinal decontamination [156] have shown some promise-their efficacy is yet to be confirmed in dialysis patients however.…”