Full text of DOI:10.1111/j.1755-6686.2001.tb00160.x

Microbiological survey of dialysate:
Vantage of use of sterile bag concentrate
S. Pansini, R. Degaetano, D. Boccassini, E. Turi
Nephrology and Dialysis Unit, Molfetta, Italy
Summary
Haemodialysed patients are exposed to nearly 400 litres of dialysis water weekly. The bacterial contamination of treated
dialysate and water induces acute pyrogenic reactions or chronic damage and cytokine activation.
The aim of this study was to value the microbiological parameters of dialysis water and dialysate of our monitors by
bacterial culture (measured as colony forming units [CFU]) of water samples at 37 °C after 48 hours, at 22 °C after
7
2 hours and after seven days, and by measuring endotoxin levels (endotoxin units [EU]).
In our centre, there are 16 monitors (6 monitors use sterile dialysate fluid and 10 monitors use non sterile dialysate
fluid). The chemicals used for disinfection are chlorine and paracetic acid. Water samples were taken under sterile
procedures every three months for a year.
No bacteria were found in the samples of water of the dialysis ring; EU were lower than the limit value of 0.25 EU/ml
fixed by the European Pharmacopoeia.
The concentration of CFU and EU of the dialysate, taken from monitors with a sterile bag, were lower than those
of other monitors (p < 0.05 t Student test). However, the levels of CFU/ml and EU/ml of dialysate samples, taken
from monitors with a non-sterile bag, were lower than the guideline value of the European Pharmacopoeia (v.n. CFU
<
50 CFU/ml and EU < 0,05 EU/ml).
Frequent examination of CFU and EU is essential to reduce the damage caused by the use of contaminated water,
therefore the goal of future dialytic techniques will be the use of “sterile dialysate”.
Key words
–
–
–
Dialysis water
Endotoxin units
Colony forming units
AEMODIALYSED PATIENTS are exposed to nearly 400 fer due to back-filtration; furthermore, the absorption capacity
H
litres of dialysis water weekly. Therefore, the microbiolog- is exhausted if the dialysate is heavily contaminated (6, 7). Bac-
ical quality of dialysis water is very important for the biocom- terial products transferred across the membrane may produce
patibility of the haemodialytic treatment. The bacterial contam- an acute pyrogenic reaction (fever, nausea, vomiting, hypoten-
ination of treated water and dialysate causes acute pyrogenic sion, shivering) (1). In the absence of acute clinical episodes,
reactions or chronic damage and cytokine activation (1, 2).
small amounts of pyrogenic substances can activate circulating
Several in vitro studies show that intact dialyser membranes lympho-monocyte cells, which produce cytokines such as IL-1‚
are permeable to pyrogenic bacterial substances derived from and TNFa. These cytokines can cause acute effects: induction of
contaminated dialysate. The size of the pores of the dialyser acute-phase proteins, suppression of appetite and sleepiness
membrane is less important than the thickness and the capaci- (8). Moreover, chronic stimulation of cytokines causes more
ty of the membrane material to absorb bacterial products (3, 4). serious complications such as 2microglobulin amyloidosis,
The cellulose low-flux membranes do not have absorption hypercatabolism, malnutrition, immunodepression and endo-
capacity and are more permeable to bacterial products than thelial damage (9). Activation of endothelial cells by cytokines
synthetic high-flux membranes (5). On the contrary, synthetic can produce a down-regulation of nitric oxide and cycloxyge-
membranes present high absorption capacity due to hydropho- nase-I syntheses of endothelial cells inducing vasospasm,
bic interactions but have a more elevated risk of pyrogen trans- thrombosis and athermatous plaque formation (10).
Aim of study
Saverio Pansini graduated from technical high school in 1975; he has
worked as a technician in the dialysis unit at the hospital of Molfetta (Bari,
Italy) since February 1983. He has attended numerous courses for dialysis
technicians organised by several dialysis moni-
The aim of our study was to value the microbiological parame-
ters of dialysis water and dialysate of our 16 monitors. We used
the dialysate concentrate of 10 monitors in plastic tanks, sterile
at the beginning, but contaminated by air after opening (con-
ventional concentrate); while in the other 6 monitors the
dialysate concentrate was contained in sterile bags sealed dur-
ing the haemodialytic treatment (sterile concentrate).
tor building firms and took part in the 28th
Congress of EDTNA/ERCA in Berlin, 1999.
Saverio was co-author of a communication pre-
sented during the “infection control” session at
the 29th congress of the EDTNA/ERCA in Lisbon,
2000.
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Materials and methods
We performed physical, chemical and microbiological analysis CFU/ml and EU/ml of dialysate samples taken from monitors
of the raw water according to European standards. with conventional concentrate, were lower than the guideline
monitors (p < 0.05 t Student test). However, the media levels of
The disinfection procedures were performed in our dialysis value of the European Pharmacopoeia (v.n. CFU < 50 CFU/ml
unit using the chemicals paracetic acid and chlorine. The disin- and EU < 0.05 EU/ml for dialysate water).
fection intervals were daily after each haemodialysis. All the
dialysis monitors had an ultrafilter at the treated water inflow,
and only one of these was equipped with an ultrafilter at the Several studies have shown the transmembrane crossing of bac-
dialysate outflow. terial substances from dialysate to blood compartment either
Discussion and conclusion
The dialysate samples for CFU and EU concentrations were using cellulose low-flux membranes or synthetic high-flux
taken at the water outlets of the dialysis monitor during “water membranes (4, 5). Many authors have demonstrated acute
flushing mode” immediately before the dialytic treatment. All pyrogenic reactions and chronic effects when using contami-
water samples were obtained after rising and disinfecting the nated dialysate: the bacterial count and the LAL assay per-
taps.
The bacterial culture of dialysate samples was performed to bacterial contamination in the dialysis water (11-13).
every three months for one year and the amount of EU were The water used for dialysis in our centre was not polluted;
noted (four samples for each monitor and four samples for the whereas the CFU/ml and EU/ml concentration were lower in
dialysis water ring). dialysate taken from monitors with sterile bags. There is a
formed in water and dialysate are important to avoid risk due
The bacteriological analysis was performed by plate count minor risk of acute reaction or chronic damage using these
with 1 ml and 0.1 ml samples; the incubation times were 72 h monitors.
and seven days at 22 °C, and 48 h at 37 °C (Bioburden Vitek
Card Biomerieux) (n.v. CFU/ml < 50 in dialysate water).
Therefore, the difference of cost between the “sterile bag
concentrate” and “conventional concentrate” isn’t very signifi-
The concentration of endotoxins was measured using a cant (Lit. 18.000 vs. 15.000 respectively). In addition to the
quantitative chromogenic limulus amoebocite lysate assay (LAL cost, we have to consider the transport, the packaging and stor-
test biologik -A- Italy). The test system is calibrated in endo- age charges for conventional dialysate contained into plastic
toxin units (EU/ml) and its sensibility was 0.003 EU/ml.
The results were expressed as the means ± SD (Table 1).
tanks.
In conclusion, frequent examination of CFU and EU is
essential to reduce potential water contamination; but the goal
of future techniques will be a “sterile dialysate” to assure a more
physiologic dialysis.
Table 1
CFU/ml
LAL EU/ml
DIALYSATE-Monitors
with sterile bags
1.46 ± 0.94
0.08 ± 0.05*
Received: October 2000
Reviewed: November 2000
Revised: February 2001
Accepted: April 2001
DIALYSATE-Monitors
with non sterile bags
WATER of the ring
4.76 ± 7.53
2
0.45 ± 0.42*
0.14
*
p < 0.05 EU non-sterile vs. sterile bag (t Student test)
Results
Address for correspondence
Saverio Pansini
No bacteria were found in the dialysis water ring; the EU con-
centration was lower than the limit value of 0.25 EU/ml accord-
ing to the European Pharmacopoeia.
Via Salvo d’Acquisto 31
70056 Molfetta
The CFU and the EU of the dialysate taken from monitors
with sterile bags, were lower than the concentrations of other
Italy
e-mail: m.virgiliomolf@tin.it
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