Arena Service Manual
have increased beyond recommended levels. Increased levels give
clues where the problem source may be located.
A water treatment system diagram marking all possible sampling
site locations can be of a tremendous benefit. By identifying each
sample site with a number and assigning that number to each
sample taken, it would be easier to locate a problem source. Trend
analysis also can be accomplished with this information and
potential problems be averted before developing further.
Historically, some aspect of the water treatment system has proven
to be the major cause of contamination. Test results that indicate
high microbiological contamination in the dialysis machine but no
contamination in the water treatment system often indicate that a
premachine source of contamination has been overlooked.
The time that samples are taken could be an important clue.
Samples immediately following disinfection are not going to be a
good indicator of adequate disinfection. But, if done and they
show signs of contamination, this would be reason to suspect
problems with the disinfection procedure or dead legs in the
distribution system. High levels of bacteria found shortly after
disinfection could point out the need to disinfect more frequently
or to replace filters more frequently.
Check the process of taking samples to ensure an aseptic technique
is used to avoid contaminating the sample. Make sure the sample
is taken mid-stream, after about 30 seconds of flow (Bland &
Favero, 1990).
Samples must be assayed within 30 minutes or refrigerated and
assayed within 24 hours (AAMI, 1990, pp. 81-94).
Take new samples before starting to analyze the problem. This
will give a base line to make comparisons of past and future data.
Make sure the lab is using the proper technique for assaying the
samples. A pour plate, spread plate, or membrane filter technique
should be used (AAMI, 1990, pp. 81-94). Make sure the
measurement is done via pipette versus the calibrated loop method
(Bland & Favero, 1990). The culture medium should be trypticase,
soy agar, or standards methods agar, and incubation should be at
37° C. The colonies should be counted after 48 hours. The
objective of the assay at this point is to find the total bacteria count
(AAMI, 1990, pp. 81-94).
9.13.2 Identify Contributors
The city water systems can always be considered a contributor as
small amounts of bacteria may always be present. However, with
9-44 157-1278-916, Rev A
March 2004
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