BWT AQU@Sense MB

The colony-forming units (CFU) have
been the standard for measuring the
microbiological quality of PW and WFI
for over 100 years. The regular determination
with the plate-count method is
slow, expensive and error-prone.
Pharmacopoeias therefore advocate the
use and validation of alternative methods
to determine microbiological quality.
By applying rapid microbiological methods
(RMM), information about microorganisms
is available promptly. Action can
be taken as soon as microbial deviations
occur – not just fi ve days afterwards, as
with the compendial method. The functional
advantages also enable improvements
in the quality of the test routines,
where correct qualifi cation and implementation
are crucial. For additional
information, see European Pharmacopeia
(Ph. Eur.) 9.2 chapter 5.1.6 and United
States Pharmacopeia (USP) 41, chapter
<1223>.
The USP aims to provide guidance on
selection, evaluation and use. Ph. Eur.
sees the potential for improving the
effectiveness of microbiological monitoring
and the quality of pharmaceutical
products, and therefore aims to facilitate
the implementation and use of alternative
rapid microbiological methods.
CFU AS THE YARDSTICK OF
MICROBIOLOGY
Colony-forming units (CFU) are still the
decisive factor in assessing microbiological
quality, but even pharmacopoeias
criticise the value of the data generated.
The USP describes the unit of CFU as an
estimate rather than a precise quantifi -
cation as, for example, only 0.1–1% of the
existing pathogens in drinking water are
counted as CFU. It is therefore proposed
that CFU should not be regarded as the
exclusive measure for microbiological
evaluation.
According to Ph. Eur., the effective limits
were set without a quantitative defi nition.
Therefore, while for example the
arbitrarily defi ned 10 CFU/100 ml permitted
for WFI has been validated.
It is clear that even pharmacopoeias
themselves clearly describe the limits
and restrictions of the compendial CFU
count. Therefore, it is time to change
towards forward-looking, cutting-edge
technologies, which offer signifi cant
benefi ts for quality managers and microbiologists.

The time has come to use more accurate and rapid methods to
determine the level of micro-organisms in water. BWT recommends
fl ow cytometry, whereby a laser is used to count the cells of a water
sample in the AQU@Sense MB measurement chamber. A fl uorescent
liquid is used to dye the cells’ DNA in the sample to ensure reliable
and accurate detection. This prevents extraneous particles from
being counted as ‘false-positives’ and allows for detailed sample
analysis Operators can therefore obtain the total microbial cell count
(TCC). RMM enable users to accurately assess water quality at any
time, ensuring safer and more effi cient plant operation.

FOCUS ON ONE ASPECT OR KEEP THE OVERVIEW
The AQU@Sense MB has two operating modes. It can be permanently
installed at a measuring point to automatically record the microbiological
quality of critical utilities at regular intervals. Alternatively,
manual grab samples from multiple sample points can be analysed by
a single AQU@Sense MB. Action can be taken immediately, if your set
limits are exceeded. Promptly. Not after fi ve days, as before.
FREEDOM TO CHOOSE
The online use of RMM has many interesting features, one of which is
the process control in systems that generate PW and WFI. Another
advantageous application is the monitoring of the water quality in
storage and distribution systems.
Identify the risk of contamination at an early stage. Initiate sanitisation
as appropriate and verify its effectiveness right away.