IATP Hog Report - Institute for Agriculture and Trade Policy

Section 2
use of penicillin and tetracycline as subtherapeutic animal feed
additives. 106
In 1988, the IOM committee issued its report. 107 Citing one controlled
study, it noted that fecal coliform from a herd of pigs fed and treated with
antibiotics continuously for 13 years exhibited a 90% resistance level to
tetracycline. The herd was then kept antibiotic free and closely monitored.
It took an additional 13 years for resistance levels to drop to 30%.
The IOM committee noted studies showing compelling evidence of a
human health hazard arising from antibiotic-resistant Salmonella
originating in animals fed subtherapeutic levels of antibiotics. However, it
also noted a lack of sufficient direct evidence to quantify the human health
hazard from antibiotic-resistant pathogenic bacteria created by the use of
subtherapeutic penicillin or tetracycline additives in animal feed.
Nevertheless, the committee concluded that, on the basis of the available
indirect evidence, "these antibiotics in subtherapeutic concentrations do
present a hazard to human health and may contribute to a percentage of
deaths annually in the United States from salmonellosis." 108
In 1995, FDA approved subtherapeutic use of one of the fluoroquinolone
antibiotics in poultry drinking water to control illnesses caused by E. coli
bacteria. 109 The fluoroquinolones are used to treat Campylobacter and
other bacterial infections in humans. Campylobacter, a bacterium that is
also present in chickens, is not killed by the low levels of fluoroquinolone
added to poultry drinking water to control E. coli. Instead, as had
happened in Europe earlier when fluoroquinolone feed additives were
approved, Campylobacter developed resistance to fluoroquinolones. 110
However, trends are not direct evidence of linkage or causation.
In May 1999, The New England Journal of Medicine published a
Minnesota study that went further in establishing such a direct link. 111 The
Minnesota study documented that DNA fingerprints in quinolone-resistant
Campylobacter jejuni from domestically produced poultry were identical
to those in the resistant C. jejuni from domestically-acquired infections in
humans. 112 Yet, following the study's release, the animal health industry
contended "no significant risk to humans [stemming from antibiotic feed
additives for animals] has been documented," and warned farmers and
veterinarians to "remain informed about potential political threats to drug
availability, threats based on fear and speculation rather than science and
data." 113
On January 26, 1999, the FDA released for comments a report entitled, "A
Proposed Framework for Evaluating and Assuring the Human Safety of
the Microbial Effects of Antimicrobial New Animal Drugs Intended for
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