Poultry International - March 2018 - 23
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PoultryInternational ❙ 23
Observational and other studies have generally
yielded similar results.
For example, in one randomized control trial,
broiler chickens were infected with strains of
Campylobacter known not to be resistant to
fluoroquinolone antibiotics. Days later, chickens in the experimental group were given the
antibiotics, while the control group was not.
Flouroquinolone resistance rapidly emerged in
the Campylobacter collected from the exposed
birds, but not in the non-treated birds.
Commensal bacteria tend to be easier to study
than pathogens. Research has shown that on-farm
antibiotic use can and does lead to an increase in
resistance among commensals, which can then
transfer to more harmful bacteria.
Are resistant bacteria on farms or
feedlots infecting people?
Yes. Resistant bacteria, both pathogens
and commensals, pose a risk to humans directly
Observational studies and other types of
research confirm that foodborne and zoonotic
pathogens can be transmitted from animals to
people. The routes of transmission are complex,
but have three primary pathways: direct contact
with infected animals, food and environmental
transmission. There is no way to quantify which
route is the most significant.
Randomized trials and observation studies
have demonstrated that commensal bacteria from
animals can temporarily establish themselves in
humans, for instance, when people have contact
with animals carrying the bacteria or handle their
Strong scientific evidence further shows that
these commensals can and do share their resistance genes with human commensals and pathogens. The presence of antibiotics seems to make
exchanges of resistant genes more likely, but it
can happen without them.
In one U.S. study, broiler chickens were given
tretracycline in feed, and investigators studied its
March 2018 ❙ www.WATTAgNet.com