Mystery Moves Toward Resolution
By Sharon Durham
June 14, 2001
A variation on the age-old question of
which came first--the chicken or the egg-- is one
Agricultural Research Service scientists
are pondering as they search for the source of a foodborne bacteria that causes
human illness. The scientific riddle the researchers want to solve is how each
new generation of chicks is infected with Campylobacter.
To find the answer, ARS researchers traveled to Iceland, where poultry is
produced in a closed system. Breeder eggs are obtained from Sweden, hatched in
Iceland and quarantined at rearing farms. It is an integrated approach with a
high degree of control.
ARS scientist Norman Stern and his colleagues at the
Poultry Microbiological Safety Research
Unit, Athens, Ga., believe they have found one major source of
Campylobacter: the fertile chicken egg. Historically, possible sources of
the bacteria were thought to be the feed, wild birds, well water, bird fluff
and pads in the cages.
Through inoculation studies, scientists showed that Campylobacter
couldn't survive long in dry conditions, eliminating bird feathers and hatchery
transport paper pads from the list of possible sources. Other studies showed
that feces on the surface of eggs were an unlikely source of contamination.
Thus, attention focused on transmission of the bacteria in the egg itself.
By sequencing genetic material called DNA, a specific gene in
Campylobacter was isolated and used as a marker to identify identical
organisms. Evidence shows that the same Campylobacter isolate was
detected in poultry production plants about 20 miles apart. The only way the
organism was able to travel from one location to the other was in the moist
confines of the egg.
The research may lead to understanding the major sources involved in
transmitting the bacteria--and may help reduce or prevent Campylobacter
from entering the marketplace.
A more detailed story on the research appears in June 2001 issue of Agricultural Research magazine.
ARS is the chief scientific research agency of the
U.S. Department of Agriculture.
Scientific contact: Norman Stern, Poultry Microbiological Safety
Research Unit, ARS Richard B. Russell Research Center, Athens, Ga., phone (706)
546-3516, fax: (706) 546-3771, firstname.lastname@example.org.