It is time for action: this use contributes to bacterial
resistance in humans
By Dr. Steve Heilig
Antibiotics are arguably the single most important
and widely used medical intervention of our era. Almost every
medical specialty uses antibiotic therapy at some point. These
drugs have prevented incalculable suffering and death and
are perhaps still the closest medications we have to a "magic
bullet."
Of course, bad bugs can bite back, and
bacterial adaptation and resistance
were reported soon after antibiotics were first used. The
struggle to stay one step ahead of pathogens has been widely
described and debated.
Correcting the overuse of antibiotics
in human medicine has gradually become a priority, with slow
but heartening progress being gained in this darwinian race.
Still, the rise of multidrug resistance and the ready transfer
of resistant traits among pathogens require heightened action
if we are to prevent increasing outbreaks of infections that
become more difficult, or even impossible, to treat.
One essential course of action is to minimize
any and all causes and reservoirs of antibiotic resistance.
Besides medical use in humans, there is the troubling issue
of use in agriculture, specifically in livestock production.
Antibiotics have long been routinely used
not only for the treatment of infections, but also as a means
of getting animals to market faster by growth promotion. Controversies
about these practices have resulted in numerous reports, dating
back decades, urging more caution or outright bans on the
practice.
The World Health Organization and other
leading medical and public health bodies have advised that
animals not be dosed with antibiotics used in humans -- to
little avail here in the United States to date, even though
our own Food and Drug Administration (FDA) took this position
as far back as 1972.1
Still, many longtime observers of the
issue were surprised -- or even shocked -- to learn the true
extent of antibiotic use on farms. A recent report estimates
that upward of 70% of all antibiotics
manufactured are used in agricultural settings.2
Although the exact percentages are uncertain,
agricultural antibiotic use is apparently more substantial
than previously thought. And the type of use is worrisome
because it involves continual, subtherapeutic doses that would
seem to provide ideal environments for the selection of resistant
pathogens.
The introduction of new molecular epidemiologic
tools has heightened the worry because these tools have been
used to show that resistant bacteria originating on farms
are finding their way into humans.3,4,5,6,7,8,9,10
The extent of this epidemiologic "spillover"
to date is uncertain -- assertions of the extent of bacterial
resistance arising from farms vary widely -- and this needs
to be a higher research priority. But there is no question
that the phenomenon does exist.
Recognizing this risk, the American Medical
Association's house of delegates recently adopted a policy
stating that the association "urges that nontherapeutic
use of antimicrobials in animals that are also used in humans
should be terminated or phased out based on scientifically
sound risk assessments."11
Reaction from the pharmaceutical industry,
in the guise of a trade association of manufacturers of animal
drugs, was swift. The Animal Health Institute erroneously
claimed that "The assertion that there is increasing
evidence that resistance developed in animals is spreading
to humans is not true," and it went on to oppose any
further restriction on agricultural use.12
As a case study of such profit-motivated
opposition, Bayer Corporation is vigorously contesting the
FDA's proposal to withdraw a widely used class of antimicrobial,
fluoroquinolones, from agricultural use.
These medications are used only therapeutically
in agriculture, but they are used to combat some of the same
bacterial pathogens that are treated with the same drugs in
human medicine. Hence, there is a high risk of resistant strains
finding their way from animals to humans.13 Abbot Laboratories,
the other major manufacturer of fluoroquinolones, showed admirable
scientific judgment and corporate responsibility in agreeing
to the FDA's request.
Unfortunately, judging from the Animal
Health Institute's response to the AMA, we fear the drug industry's
reactions may more closely mirror Bayer's shortsighted approach.
Notably, even some forward-thinking agricultural leaders are
now questioning the wisdom of such stonewalling.14
Admittedly, we tend to give more credibility
to those who do not have any financial interest in the status
quo. Leading experts unequivocally state that our current
practices of feeding antibiotics to animals goes against "a
strong scientific consensus that it is a bad idea" and
that the long stalemate on this issue constitutes a "struggle
between strong science and bad politics."15
The intentional obfuscation of the issue
by those with profit in mind is an uncomfortable reminder
of the long and ongoing battle to regulate the tobacco industry,
with similar dismaying exercises in political and public relations
lobbying and even scandal.16 As with tobacco control, science
and health concerns should take precedence over profit in
regulating the overuse of antibiotics in the production of
meat and other agricultural products.
Antibiotics do have a place on farms,
but the benefits of their use can likely be preserved while
minimizing harm. We need to learn more about the extent of
risk, but the delay tactic of allowing current practices to
continue while "more research" is conducted is unacceptable.
Enough is already known to justify a more
cautious, preventive approach.17 Other nations are ahead of
the United States in this regard and have banned routine agricultural
use, with demonstrable benefit in reduced bacterial resistance.18
We call on the FDA or legislators to,
in the coming year, ban the nontherapeutic agricultural use
of antibiotics. This ban should be lifted only if it is scientifically
proved, in unbiased studies, that this use does not contribute
to bacterial resistance in humans.
Producers of agricultural antibiotics
should be required to submit data on the specific antibiotics
used, in sufficient detail to track usage and resistance trends.
Bayer should reverse its opposition to the ban on fluoroquinolones.
Finally, individual and business consumers of meat should
begin to demand that the meat they purchase be grown without
the routine use of antibiotics.
For information on the growing campaign surrounding
this issue, see www.keepantibioticsworking.com.
Western
Journal of Medicine January 2002;176:9-11
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