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» Sonderthema: Mikrobiologische Methoden in der Lebensmittelanalytik 653
tection to help determine the source
of the contamination. And, the system
does all this with a ready-to-use medium
that is simply combined with a water
sample.
Many users may stop after detecting
coliforms. Detecting any coliforms in the
sample is enough for them to indicate that
further action is required. But, the test
makes it very easy to take the next step
if coliforms have been found. Using the
same sample, simply use a long wavelength
ultraviolet light in a darkened environment
to check for fluorescence. If
the sample produces a bright blue fluorescence,
the coliforms that have been detected
include MUG-positive E. coli bacteria.
For users solely interested in detecting
fecal coliforms, the Colitag system includes
a procedure that utilizes a 20-hour
incubation at 44.5°C to exclude non-fecal
coliforms from detection. Both MUG positive
and MUG negative E. coli can be further
identified through the use of ultraviolet
light and Kovac’s reagent.
Within the fecal coliforms procedure,
if the sample has turned yellow and no
bright blue fluorescence has been seen
to indicate the presence of MUG-positive
E. coli, the sample can be further tested
for MUG-negative E. coli. To test for MUGnegative
E. coli, add a few drops of Kovac’s
reagent to the sample. If a reddish purple
Detecting coliforms and E. coli in water
samples using Colitag
1. Start with a 100 mL water sample. If the sample is chlorinated,
add 10 mg of sodium thiosulfate to neutralize the chlorine.
2. Add the entire contents of a premeasured vial of medium. Mix
briefly to dissolve the medium, and place the sample into an incubator
set at 35°C for 24 hours.
3. After the incubation, check the sample for a vibrant yellow color.
If the sample is yellow, coliforms are present. If the sample has
remained colorless, the test has not detected even one coliform
in the 100 mL sample.
colour forms on the surface of the water,
the sample is positive for MUG-negative
E. coli.
How does the system so easily detect coliforms
and E. coli? The system’s medium is
engineered to detect enzymes characteristic
of E. coli and the coliform group. Resuscitation
of target organisms is accomplished
through a patented technology,
which combines a low pH medium and
nutrients that provide a favorable environment
for resuscitation of weak or injured
cells.
After the bacteria are rejuvenated at
this low pH, the medium adjusts the pH to
a neutral level. This rise in pH aids growth
of E. coli cells to levels more readily detected.
In addition, this rise in pH makes
it easier to see the system’s colour and
luorescence indicators.
Erkrankungen durch
Nahrungs- und Genussmittel
Ursachen – Diagnostik –
Therapie – Prävention
Herausgegeben von Prof. Dr. Dr.
Jürgen Stein, Prof. Dr. Martin
Raithel, und Prof. Dr. Manfred Kist.
2011. XVIII, 510 S. 122 Abb., 79 Tab.
Gebunden. € 78,– [D]
ISBN 978-3-8047-2565-2
E-Book PDF: € 78,– [D]
ISBN 978-3-8047-2969-8
E-Books sind online als PDF zum Download
erhältlich unter www.buchoffizin.de
Renommierte Ernährungswissenschaftler und -mediziner,
Pharmazeuten, Gastroenterologen und Infektiologen
stellen in diesem umfangreichen Werk alle Aspekte
nahrungs- und genussmittelbedingter Erkrankungen
systematisch dar.
Fundierte Informationen über Ursachen und
Pathogenese, Klassifikation und Epidemiologie,
Diagnostik und Therapie sowie Prävention so gut
wie aller ernährungsbedingten Krankheiten ermöglichen
dem Leser eine bedarfsgerechte, individuelle Behandlung
auch außergewöhnlicher Fälle.
„Essen ist ein Bedürfnis, Genießen ist eine Kunst.”
(François de La Rochefoucauld)
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