This scanning electron microscope image shows the
characteristic spiral, or corkscrew, shape of C. jejuni cells and
related structures. Click the image for more information about
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Making Campylobacter Easier to
Count By Sharon
October 15, 2004
A new agar gel has been developed by Agricultural Research
Service (ARS) scientists to isolate and
count hard-to-see, microscopic organisms that can cause food poisoning.
For researchers in the laboratory, counting the number of
colonies of Campylobacter bacteria growing in round petri dishes can be
like trying to count the number of raindrops on your cars windshield
after a light rain.
Historically, agar--the gel material used to grow
Campylobacter in tissue culture--has blood components, or charcoal, as
ingredients. These components give the agar a dark color. Unfortunately,
Campylobacter colonies are clear, often appearing as water droplets on
the agar. Now ARS food technologist J. Eric Line of the
Microbiological Safety Research Unit in Athens, Ga., has found a way to
make the task a whole lot easier.
Line has found that exposing Campylobacter to low levels
of a chemical called triphenyltetrazolium chloride (TTC) was not detrimental to
bacterial growth, yet imparted a deep-red to magenta color to the
Campylobacter colonies. The new agars used for Campylobacter
growth are translucent, resulting in a contrast of dark colonies on a
translucent background. This contrast makes it easier for researchers to
isolate and count Campylobacter. The new technology also allows
researchers to count the bacteria on light boxes or electronically.
Campylobacter is a food-borne pathogen found in numerous
raw or mishandled foods, including poultry. This illness is characterized by
symptoms such as diarrhea, cramping, abdominal pain and fever. The agar can be
used in laboratories to conduct diagnostic testing.
about this research in the October 2004 issue of Agricultural Research
ARS is the U.S. Department of
Agricultures chief scientific research agency.