Researchers Trace Food Poisoning Bug Back to Chickens and Livestock
[September 26, 2008]
a GenomeWeb staff reporter
Source of Article: http://www.genomeweb.com/issues/news/149643-1.html
In a paper appearing online today in
“The idea was that we wanted to know where this thing comes
from,” lead author Daniel Wilson, a post-doctoral researcher at the
Although most people may think of Escherichia coli
and other bugs as food poisoning culprits,
There have been a number of different hypotheses about where
disease-causing C. jejuni come from. Because
the bug causes gastroenteritis, it’s easy to blame food sources. But that’s not
necessarily the case,
In an effort to determine where human-infecting C. jejuni were coming from, Wilson and his colleagues compared the genetic sequences found in human campylobacteriosis cases with those from potential source sites.
They obtained 1,231 C. jejuni
isolates from human samples taken in
Because Campylobacter is very diverse and there’s overlap between some C. jejuni populations, Wilson said, they couldn’t use the presence or absence of specific alleles to distinguish bacterial populations. Instead, the researchers compared the frequency of these alleles in different populations.
Using this “evolutionary approach,” they traced the 256 different C. jejuni genotypes back to their likely sources. Their results suggest that 96.6 percent of human campylobacteriosis cases are caused by C. jejuni populations carried by chickens, cattle, sheep, and pigs.
Bacterial populations associated with chickens caused more than half of all cases tested. Although it was more difficult to distinguish C. jejuni found in cattle from those found in sheep, the results suggest that cattle populations caused just over a third of cases, while sheep populations caused around four percent. Meanwhile, the researchers detected Campylobacter from pigs in less than one percent of campylobacteriosis cases.
In contrast, populations carried by wild animals appear to be responsible for just 2.3 percent of cases, while other environmental isolates were linked to 1.1 percent of cases.
These results differ from research published in 2005
suggesting livestock played a minor
role in campylobacteriosis — a discrepancy that
may be explained by differences in samples sizes or in analytical approaches,
To address this possibility, his colleagues are currently
collecting samples in
The work also provides clues about the bug’s transmission route, though that is usually more difficult to discern than source information. While it is unlikely that the environment is the main transmission route in the community tested, it is unclear whether C. jejuni is transmitted to humans through infected food or via another route.
For instance, because
If it turns out, as the researchers suspect, that food is
the transmission route from livestock to humans, there are three stages at
which you could prevent Campylobacter infections, Wilson explained —
first at the source, by reducing the incidence of C. jejuni
in farm animals. It may also be possible to reduce C.
jejuni in meat during food processing stages as
well as during food preparation. By educating the public about good food
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