1. Does the use of antibiotics in CAFO-raised animals contribute to antibiotic resistant organisms that impair human health? Read the Consumer’s Union paper in the readings folder, and the response from the Meat Institute, and use your best scientific literacy skills to ask: are the authors credible (and who are they?) What are the biases? What was the purpose of each study and what can be believed? Are there citations? Do a careful analysis in a minimum of 10 sentences – I would a thoughtful answer based on the 2 papers to read. Use other papers in the readings as well for full credit.2. Summarize and evaluate factsheet_livestockslongshadow paper from the readings and answer the questions such as: Is there good evidence that the BOLD diet is truly effective? What evidence do they give? Can you research this a little further?
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The Overuse of Antibiotics in Food Animals Threatens Public Health
Antibiotics have been used since the 1940s and have led to a dramatic reduction in illness
and death from infectious diseases. But according to the federal Interagency Task Force
on Antimicrobial Resistance, “[t]he extensive use of antimicrobial drugs has resulted in
drug resistance that threatens to reverse the medical advances of the last seventy years.” 1
Since antibiotics have been used so widely and for so long, antibiotic resistance has
become a major public health threat.
In response, there has been a concerted effort by the Centers for Disease Control and
Prevention (CDC) and others to encourage doctors and patients to use antibiotics more
wisely. Unfortunately, little progress has been made to reduce the use of antibiotics on
farms, where most of these drugs are administered.
Approximately 80 percent of the antibiotics sold in the United States are used in meat and
poultry production. 2 The vast majority is used on healthy animals to promote growth, or
prevent disease in crowded or unsanitary conditions. The meat and poultry production
industry argues, however, that that there is no harm in this. They say for example that
“animal use contributes little, if anything, to the burden of human antibiotic resistance…” 3 .
A key question is, can antibiotic use in animals promote the development of hard-to-treat
antibiotic-resistant superbugs that make people sick? And if it can, are the illnesses rare
occurrences, and the risks theoretical, or could current usage in animals pose a serious
threat to human health.
But Consumers Union has concluded that the threat to public health from the overuse of
antibiotics in food animals is real and growing. Humans are at risk both due to potential
presence of superbugs in meat and poultry, and to the general migration of superbugs into
the environment, where they can transmit their genetic immunity to antibiotics to other
bacteria, including bacteria that make people sick.
Numerous health organizations, including the American Medical Association, American
Public Health Association, Infectious Disease Society of America, and the World Health
Organization, agree and have called for significant reductions in the use of antibiotics for
animal food production.
Pg 5 in Interagency Task Force on Antimicrobial Resistance, 2012. A Public Health Action Plan to
Combat Antimicrobial Resistance. Washington, D.C. at:
Confirmed: 80 Percent of all antibacterial drugs used on animals, endangering human health. At:
Pg 5 in American Farm Bureau Federation et al June 12, 2012 letter to Congressperson Slaughter
History of Expert Opinion
Scientific expert bodies for more than two decades have concluded that there is a
connection between antibiotic use in animals and the loss of effectiveness of these drugs
in human medicine. In 1988, the Institute of Medicine (part of the National Academy of
Sciences) concluded that “the committee believes that important, although as yet sparse,
data show the flow of distinct salmonella clones from farm animals medicated with
antibiotics in subtherapeutic concentrations, through food products, to humans, who thus
acquire clinical salmonellosis.” 4
Ten years later, the National Research Council (part of the National Academy of
Sciences) concluded that “a link can be demonstrated between the use of antibiotics in
food animals, the development of resistant microorganisms in those animals, and the
zoonotic spread of pathogens to humans.” 5
In 2003, an Expert Workshop co-sponsored by the World Health Organization, Food and
Agricultural Organization (FDA), and World Animal Health Organization (OIE)
concluded “that there is clear evidence of adverse human health consequences due to
resistant organisms resulting from non-human usage of antimicrobials. These
consequences include infections that would not have otherwise occurred, increased
frequency of treatment failures (in some cases death) and increased severity of
infections” 6 .
In 2010, the U.S. Food and Drug Administration, U.S. Department of Agriculture, and
the CDC all testified before Congress that there is a connection between the routine
use of antibiotics for meat production and the declining effectiveness of antibiotics
for people. 7 Dr. Thomas R. Frieden, Director of the CDC, noted that “there is strong
scientific evidence of a link between antibiotic use in food animals and antibiotic
resistance in humans.” 8
Most recently in 2012, the FDA stated “Misuse and overuse of antimicrobial drugs
creates selective evolutionary pressure that enables antimicrobial resistant bacteria to
increase in numbers more rapidly than antimicrobial susceptible bacteria and thus
Pg. 2 in Institute of Medicine (IOM). 1988. Human Health Risks with the Subtherapeutic Use of
Penicillin or Tetracyclines in Animal Feed. National Academies Press. Washington, D.C.
Pg. 6 in IOM. 1998. The Use of Drugs in Food Animals: Benefits and Risks. National Academies Press.
Pg. 1 in WHO/FAO/OIE. 2003. Joint FAO/OIE/WHO Expert Workshop on Non-Human Antimicrobial
Usage and Antimicrobial Resistance: Scientific assessment, Geneva, December 1-5, 2003. At:
Hearing: Antiobiotic Resistance and the Use of Antibiotics in Animal Agriculture, Subcommittee on
Health, Energy and Commerce Committee, U.S. House of Representatives, July 12, 2010
Letter from Thomas R. Frieden, Director, Centers for Disease Control and Prevention, to Keeve
Nachman, Program Director, Farming For the Future, at http://www.livablefutureblog.com/wpcontent/uploads/2010/11/ar-m455n_20101129_182057.pdf
increases the opportunity for individuals to become infected by resistant bacteria.” 9 Also
in 2012, the FDA, in its final rule banning certain extralabel uses of cephalosporin
antimicrobial drugs in certain food producing animals, stated “In regard to antimicrobial
drug use in animals, the Agency considers the most significant risk to the public health
associated with antimicrobial resistance to be human exposure to food containing
antimicrobial-resistant bacteria resulting from the exposure of food-producing animals to
Nevertheless, the livestock industry continues to argue that while antibiotic use may have
something to do with antibiotic resistance in bacteria on the farm, it is not an important
human health issue, and little change in current practices are needed.
What Happens on the Farm
Numerous studies have demonstrated that routine use of antibiotics on the farm promotes
drug-resistant superbugs in those facilities. Some of the most dramatic evidence came as
a result of FDA approval of flouroquinolones–a class of antibiotics that includes Cipro
(ciprofloxacin), which has been used in poultry production since 1995. By 1999 nearly
20 percent chicken breasts sampled contained ciprofloxacin-resistant Camplobacter, a
disease-causing bacteria. 11 After a long fight in the courts, FDA finally banned use of the
drug in 2005, at which point nearly 30 percent of C. coli found in chicken breasts were
ciprofloxacin resistant; by 2010, resistance to ciprofloxacin had declined to 13.5
The reason for this is that when you feed antibiotics to animals, the bacteria in and
around the animals are exposed to the drug, and many of them die. But there are always
some that the drug can’t kill, and those survive and proliferate. Voila, superbugs.
While not disputing these facts, the industry argues essentially that what happens on the
farm stays on the farm. There may be some superbugs there, but they don’t affect
people. There are two main routes, however, by which superbugs can leave the farm and
infect humans. One is a direct route, in meat and poultry products, and the other is an
indirect route through the environment.
Pg. 3 in Food and Drug Administration (FDA). 2012. Guidance #209: the Judicious Use of Medically
Important Antimicrobial Drugs in Food-Producing Animals. At:
Pg. 738 in FDA. 2012. New Animal Drugs; Cephalosporin Drugs; Extralabel Animal Drug Use; Order of
Prohibition. Federal Register, Vol. 77(4). http://www.gpo.gov/fdsys/pkg/FR-2012-01-06/pdf/2012-35.pdf
Smith KE, Besser JM, Hedberg CW, Leano FT, Bender JB, Wicklund JH, Johnson BP, Moore KA,
Osterholm MT et al. 1999. Quinolone-resistant Camplybacter jejuni infections. New England Journal of
Medicine, 340(20): 1525-1532. At:
Food and Water Watch. 2012. Antibiotic Resistance 101: How Antibiotic Misuse on Factory Farms
Can Make You Sick. 21pp. At: http://documents.foodandwaterwatch.org/doc/AntibioticResistance.pdf
Superbugs Move From Farm to Kitchen
Once they appear on the farm, superbugs most definitely move from the farm to the
kitchen, via uncooked meat and poultry. Consumer Reports tests of chicken in both
2006 13 and 2010 14 revealed widespread presence of antibiotic-resistant pathogens in
retail poultry products. In both years, more than two thirds of chicken samples were
contaminated with Salmonella and/or Campylobacter, and more than 60 percent of those
bacteria were resistant to one or more antibiotics.
The industry argues that even this is not a concern because people know to cook poultry
thoroughly. Indeed they do, but packages can drip in the refrigerator, or cutting boards
can become contaminated, as well as other problems. There aren’t good data on how
frequently this causes illness, especially difficult-to-treat illness, because most people just
ride out an infection and it fades into the background of the estimated 48 million cases of
food borne illness we have annually in the US.
But occasionally a superbug outbreak is serious enough to command the attention of the
Center for Disease Control. One such case occurred in 2011, in which ground turkey was
linked to 136 illnesses and one death, all caused by a strain of Salmonella resistant to four
different antibiotics, ampicillin, streptomycin, tetracycline and gentamicin. 15 Some 36
million pounds of ground turkey were recalled.
Another case was ground beef from the Hannaford grocery store chain in New England
linked in 2011 to 19 infections and at least seven hospitalizations, all caused by a strain
of Salmonella resistant to multiple antibiotics, including amoxicillin/clavulanic acid,
ampicillin, ceftriaxone, cefoxitin, kanamycin, streptomycin, and sulfisoxazole. 16
Superbugs Move From Farm to the Environment
Superbugs can also spread beyond the farm and threaten public health through
environmental transmission. This can happen in various ways, particularly via workers,
or farm runoff. Once farm-raised superbugs make it off the farm, they can exchange
genetic material and give their resistance to other bacteria, even of other genera and
species, that have never been anywhere antibiotics. This can happen in lakes, in wild
animals, and even in the human digestive tract.
Workers are particularly likely to pick up resistant bacteria from animals and take them
elsewhere. A study of poultry workers in the Delmarva peninsula found they were 32
times more likely to carry gentamicin-resistant Escherichia coli, and more than five times
more likely to carry multi-drug resistant E. coli, compared to other community
Consumer Reports, 2007. Dirty Birds. January 2007, pp. 20-23. Consumers Union.
Consumer Reports, 2010. How safe is That Chicken. January 2010, pp. 19-23. Consumers Union.
Centers for Disease Control (CDC). 2011. Investigation Update: Multistate Outbreak of Human
Salmonella Heidelberg Infections Linked to Ground Turkey. At:
CDC. 2012. Investigation Update: Multistate Outbreak of Human Salmonella Typhimurium infections
Linked to Ground Beef. At: www.cdc.gov/salmonella/typhimurium-groundbeef/010512/index.html
members. 17 A study performed in the Midwest found methicillin-resistant
Staphylococcus aureus (MRSA) in 70 percent of the pigs and 64 percent of the workers
at one facility, while no MRSA was found in pigs or workers at a facility in another state,
strongly suggesting that the MRSA strain moves between pigs and humans. 18 Indeed, a
careful genetic analysis has found that a particular MRSA strain found in pigs (e.g.
ST398) originated as a methicillin-susceptible S. aureus (MSSA) in humans, jumped into
pigs, where it acquired resistance to methicillin and tetracycline, and then jumped back to
humans, where it’s known as livestock-associated MRSA (LA-MRSA). 19 This LAMRSA (e.g. ST398) is quite prevalent in the Netherlands, where it is responsible for over
20% of all MRSA. 20
However, resistant bacteria can also escape from a large livestock operation (often known
as a confined animal feeding operation, or CAFO) by a number of routes, including via
manure applied to fields as fertilizer, 21 from trucks transporting animals, 22 the wind
leaving hog facilities 23 or even via flies attracted to the manure which can pick up and
transmit resistant bacteria. 24 A recently released study of the South Platte River found
that antibiotic resistance genes (coding for resistance to sulfonamides) were 10,000 times
higher in river sediments downstream from larger feedlots (ones with 10,000 cattle)
Price LB, Graham JP, Lackey LG, Roess A, Vailers R and E Silbergeld. 2007. Elevated risk of carrying
gentamicin-resistant Escherichia coli among U.S. poultry workers. Environmental Health Perspectives,
115(12): 1738-1742. At: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2137113/pdf/ehp0115001738.pdf
Smith TC, Male MJ, Harper AL, Kroeger JS, Tinkler GP, Moritz ED, Capuano AW, Herwalt LA and DJ
Diekema. 2009. Methicillin-resistant Staphylococcus aureus (MRSA) strain ST398 is present in
midwestern U.S. swine and swine workers. PLoS One, 4(1): e4258. At:
Price LB, Stegger M, Hasman H, Aziz M, Larsen J, Andersen PS, Pearson T, Waters AE, Foster JT et al.
2012. Staphylococcus aureus CC398: Host adaptation and emergence of methicillin resistance in livestock.
mBio, 3(1): e00305-11 At: http://mbio.asm.org/content/3/1/e00305-11.full.pdf
van Loo I, Huijsdens X, Tiemersma E, de Neeling A, van de Sande-Bruinsma N, Beaujean D, Voss A
and J Kluytmans. 2007. Emergence of methicillin-resistant Staphylococcus aureus of animal origin in
humans. Emerging Infectious Diseases, 13(12): 1834-1839. At:
Chee-Sanford JC, Mackie RI, Koike S, Krapac IG, Lin Y-F, Yannarell AC, Maxwell S and RI Aminov.
2009. Fate and transport of antibiotic residues and antibiotic resistance genes following land application of
manure waste. Journal of Environmental Quality, 38(3): 1086-1108. At:
Rule AM, Evans SL and EK Silbergeld. 2008. Food and animal transport a potential source of
community exposure to health hazards from industrial farming (CAFOs). Journal of Infection and Public
Health, 1(1): 33-39. At:
Gibbs SG, Green CF, Tarwater PM, Mota LC, Mena KD and PV Scarpino. 2006. Isolation of antibioticresistant bacteria from the air plume downwind of a swine confined or concentrated animal feeding
operation. Environmental Health Perspectives, 114(7): 10323-1037. At:
Graham JP, Price LB, Evans SE, Graczyk TK and EK Silbergeld. 2009. Antibiotic-resistant Enterococci
and Staphylococci isolated from flies collected near confined poultry feeding operations. Science of the
Total Environment, 407(8): At: http://www.jhsph.edu/sebin/q/h/AntibioticResistantEntero.pdf
compared to river sediment upstream from such feedlots. 25 The same study found these
same antibiotic resistance genes were only 1,000 times higher from sewage treatment
plants that discharge ten million gallons of effluent per day, compared to pristine
Bacteria in many environments can readily exchange genes coding for antibiotic
resistance with neighboring bacteria. Antibiotic resistance genes are often located on
mobile genetic elements, especially plasmids, transposons and integrons which can easily
move between bacteria of the same or different species, which facilitates the spread of
resistance to multiple drugs by multiple types of bacteria. 26
The industry says that 40 percent of all the antibiotics used on the farm are drugs (called
ionophores) not used in human medicine, so it doesn’t matter if bacteria become resistant
to them. However, a study by scientists from the United States Department of
Agriculture (USDA) and Cornell University involving monensin, one of the most
commonly used ionophores in cattle production in the U.S., demonstrated that use of
monensin in cattle feed and the selection of monensin-resistant ruminal bacteria lead to a
32-fold increase in resistance to bacitracin, which is used in human medicine. 27 This
study demonstrates that one cannot claim that ionophores cannot select for cross
resistance to any antibiotic used in human medicine. The study called for more
research. 28 So, it is appropriate to consider ionophore use as part of the antibiotics used
in animal agriculture.
Use of antibiotics on the farm most definitely poses a risk to human health. Antibiotic
use can promote creation of superbugs which can contaminate meat and poultry and
cause hard-to-cure disease in people.
Superbugs can also exit the farm via farm workers, wind, runoff, and wildlife. Even if
they don’t immediately cause illness, bacteria are uniquely equipped to exchange genetic
immunity via their plasmids, with other bacteria wherever they encounter them.
It is for these reasons that the public health community and FDA have been proposing to
limit use of antibiotics on livestock for more than three decades (see list
below). Consumers Union believes that as a prudent measure, we should drastically
reduce use of antibiotics on food animals, and eliminate use altogether for growth
promotion or disease prevention in healthy animals.
Pruden A, Arabi M and HN Storteboom. 2012. Correlation between upstream human activities and
riverine antibiotic resistance genes. Environmental Science & Technology, dx.doi.org/10.1021/es302657r
Marshall BM and SB Levy. 2011. Food animals and antimicrobials: impacts on human health. Clinical
Microbiology Reviews, 24(4): 718-733. At: http://cmr.asm.org/content/24/4/718.full.pdf
Houlihan AJ and JB Russell. 2003. The susceptibility of ionophores-resistant Clostridium aminophilum
F to other antibiotics. Journal of Antimicrobial Chemotherapy, 52: 623-628. At:
Pg. 627 in Ibid.
Some of the Organizations Supporting Restrictions on the Use of Antimicrobials in
American Medical Association, 2001
Adopted Resolution 508, Antimicrobial Use and Resistance, which states, in part, “AMA
is opposed to the use of antimicrobials at non-therapeutic levels in agriculture, or as
pesticides or growth promoters, and urges that non-therapeutic use in animals of
antimicrobials (that are used in humans) should be terminated or phased out”. 29
American Public Health Association, 1999, 2004
Policy Number 9908: Addressing the Problem of Bacterial Resistance to Antimicrobial
Agents and the Need for Surveillance, which urged “FDA to work for regulations
eliminating the non-medical use of …
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