Title:
EXISTENCE OF MICROBIAL CONTAMINATIONS IN ENDOTOXIN FREE DIALYSATE

Ikuto Masakane¹ ;Ikuto Masakane¹ ;Ikuto Masakane¹ ;Ikuto Masakane¹ ;Ikuto Masakane¹ ;Ikuto Masakane²

1. Yabuki Hospital ; 2. Izumi Central Hospoital

E-mail address corresponding author:
imasakan@cocoa.ocn.ne.jp

Background:
Hemodialysis therapy, by use of high permeable membrane dialyzer, has been become a common modality to treat the patients with end-stage renal disease (ESRD). It is most important to avoid microbial contaminations when we adopt high permeable membrane to ESRD patients. In several papers microbial contaminations and biofilms were recognized even if the endotoxin (ET) levels of dialysate were quite low. We evaluate the relationship between ET levels and microbial cell counts.

Methods:
RO water and dialysate were collected for the examinations of microbial culture and ET levels from six hemodialysis centers in Yamagata prefecture. Bacterial cultures were performed by R2A culture medium under the condition at 30 centigrade for 5days, and all identified bacteria were waterborne species. In this study we adopted two new technologies for the evaluation of existence and quantifications of microbial contamination. Sensi media produced by Micro Bio Co. Ltd. is a sampling tube which has culture medium and a stick-shaped color sensor inside, and needs 6 ml of sample . If the sample contains bacteria the sensor changes its color from blue to yellow responding to bacteria-derived carbon dioxide. A Digital microscope culturing system; DMCS S-12 Multi-system (produced by Micro Bio Co. Ltd.) was used to quantify the microbial cell counts. By using these instruments, we can easily and accurately get a global assessment for microbial contamination in a short duration of time.

Results:
Although the ET levels were very low or under the detectable level, bacterial growths were recognized in 5 RO water samples, in 2 central delivered dialysate samples and in 4 final dialysate samples, from these 6 centers. In our institute the levels of ET in RO water and dialysate remained under the detectable level; 1 EU/L, but microbial growths were identified. Biofilms were also detected by the swabbing method in the pipe, which connected the bed-side machine to the dialyzer. We changed the sterilization program of the distribution system and dialysis machine to eradicate microbial contaminations and biofilms. After treatment with a descaling agent we increased the concentration of sodium hypochlorite from 100ppm to 300ppm firstly and 500ppm secondly. We also added disinfection of dialysate couplers and coupler joints to the sterilization program. After the descaling procedure total microbial counts in dialysate were temporally increased but the ET levels still remained under the detectable level. Even when floating bacteria disappeared from dialysate, biofilms were still detected by a swabbing method. Now we are planning to eradicate the biofilms by use of peracetic acid.

Conclusion:
In this study we emphasize that microbial contaminations and biofilms exist even if the dialysate is ET free. By only changing the present sterilization program, which was composed of sodium hypochlorite and acetic acid, we cant eradicate the biofilms. We are hoping to obtain a positive result from our current peracetic acid trials. In this presentation we will also introduce in detail new technologies for bacterial control.

Subject:
Dialysate

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