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654 Sonderthema: Mikrobiologische Methoden in der Lebensmittelanalytik «
pH
7.0
6.2
Resuscitation
Phase
Colitag’s Patented Self-Adjusting pH Level Resuscitates Chlorine-Injured
E. coli: During the process of incubation in this low pH buffered medium,
a biological buffering component in Colitag is metabolized. This component
raises the pH to a neutral level. This rise in pH aids the growth
of E. coli cells to levels more readily detected. In addition, this rise in
pH allows the color and fluorescence indicators to be opti mally visualised.
» The Colitag P/A
Water Test Kit uses
an EPA-approved
selective and differential
medium
to detect total coliforms
and E. coli
in water samples in
16–48 hours. «
Testing Phase
0 Time [h]
24
The system’s unique medium also suppresses
the growth of non-coliform bacteria,
such as Aeromonas and some Pseudomonas,
which can mimic coliforms and
cause erroneous test results.
For detection of total coliforms, Colitag
employs ortho-Nitrophenyl-β-galactoside
(ONPG). Upon hydrolysis, ONPG produces
a distinct yellow color to indicate the presence
of coliforms. For the detection of
E. coli, the system utilizes the fluorogenic
enzyme substrate MUG. Upon hydrolysis,
MUG produces an enzyme product
that fluoresces when exposed to UV light.
A sample testing method to
detect a variety of microorganisms
in liquid samples
A new method for testing liquid samples
for the presence of microorganisms has
been developed that promises to simplify
the entire process, without compromising
accuracy.
The Filter Test System, when used
with available premixed 2 mL media ampoules,
streamlines the entire microbiological
testing process for liquid
samples – including Petri dish preparation
and evaluation, sample preparation,
culture media preparation, clean-up and
disposal.
All liquid testing systems face the challenge
of being sterile, stable and reproducible.
Especially when used to the readyto-use
media ampoules, the system can
provide unerringly consistent results. The
sample and media enriched filter assembly
easily conforms into a Petri dish, and
eliminates many of the steps and time associated
with using conventional membrane
replacement filtration systems.
The new system can be used with a wide
variety of sample types, including environmental
and bottled water, raw to finished
liquid products – including milk
and other dairy products, beer and wine,
juices and soft drinks. The system can be
used anywhere liquids and/or water is
tested for the presence of microorganisms.
The system is available with either
white or black filters to make even the
lightest colonies easy to detect, and each
lid has a magnifying circle to make pinpoint
colonies easier to identify. Each
filter is 56 mm in diameter and has a
0.45 micron pore size.
The system works by using a vacuum to
first pull a liquid sample through a disposable
filter and funnel assembly, followed
by using the same process to pull a premixed
and premeasured amount of culture
media through the filter and funnel.
The funnel is then discarded, and filter
forms its own Petri dish, which is placed
into an incubator for appropriate time
and temperature for the utilised media.
Ready-to-use ampouled culture media
is currently available for the detection and
enumeration of total coliforms and E. coli,
yeast and fungi, total bacterial counts,
aciduric microorganisms, and preservative-resistant
yeast.
The Filter test system utilizes 2 mL ampouled
media to enumerate and detect
a wide variety of microorganisms in liquid
samples. Available ampouled media
available for use with the system include:
• m-Endo Broth: Used for enumerating
coliforms and recommended by
» Dezember 2012 | DLR