antimicrobial resistance and the use of antibiotics in the ... antimicrobial resistance and the use
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WCDS Advances in Dairy Technology (2011) Volume 23: 47-58
Antimicrobial Resistance and the Use of
Antibiotics in the Dairy Industry: Facing
Consumer Perceptions and Producer
Department of Animal Science, University of Vermont, Burlington VT 05445
Take Home Messages
Antibiotics are an important tool for treatment of bacterial infections in food animals and humans.
A number of antibiotic classes are used for growth promotion and disease prevention in food animals.
Antimicrobial use for growth promotion, disease prevention, and treatment contributes to improved health and productivity of food animals, which benefits human health.
The use of antimicrobial compounds creates a selective pressure on bacterial populations and contributes to antimicrobial resistance development, which negatively impacts human health.
Antimicrobial use in food animal production is under increased scrutiny.
The use of antimicrobial compounds in food animals creates a selective pressure on bacterial populations in food animals and contributes to antimicrobial resistance in these populations.
Consumers consider antimicrobial use a relatively high concern among technologies used in food production.
The extent to which antimicrobial use in food animals contributes to human health problems associated with antimicrobial resistance is likely small but perhaps not inconsequential.
The issue is complex and controversial, and while a science-based approach is frequently advocated, emotive arguments are frequently presented.
The Issue of Antimicrobial Use and Resistance in Food
There are concerns that use of antibiotics in food animals contributes to the development of resistance in foodborne pathogens which can be transferred to humans and presents a threat to human health. There are also specific concerns that the routine exposure of food animals to low doses of antimicrobials that are also used in human medicine limits the ability to treat human infections with these classes of drugs. Appropriate and prudent use of antimicrobials and antimicrobial resistance are important issues for agriculture, biomedical science and society.
Recent Events In The US Highlighting The Issue
In February, 2010 Katie Couric of CBS News presented a special report entitled “Animal Antibiotic Overuse Hurting Humans? - Katie Couric Investigates Feeding Healthy Farm Animals Antibiotics. Is it Creating New Drug-Resistant Bacteria?” (Couric, 2010a). In an accompanying news report Ms. Couric reported on “Denmark‟s Ban on Antibiotics in Livestock” (Couric, 2010b). The first report focused on health issues experienced by poultry and swine farm workers in the U.S., specifically associating human infections caused by methicillin resistant Staphylococcus aureus (MRSA) in these individuals with antibiotic use on the farms where they worked. The second report described the “Danish experiment” where Denmark has banned the use of subtherapeutic antibiotics in livestock. The reports made numerous references to “factory farms” where “animals are packed into confinement pens”, “antibiotics are used to keep disease from spreading like wildfire” and “the same classes” of antibiotics that are used to treat infections in humans are given to animals that are “not sick.” The reports indicated “MRSA has been found in the nation‟s meat supply,” suggested that “Americans may be acquiring drug-resistant MRSA - not from eating, but from handling tainted meat from animals that were given antibiotics,” and that “Danish scientists believe if the U.S. doesn't stop pumping its farm animals with antibiotics, drug- resistant diseases in people will only spread.” Following these news reports, a coalition of agriculture advocacy groups including the American Association of Bovine Practitioners, the American Association of Swine Veterinarians, American Farm Bureau Federation, and the National Pork Board responded suggesting that they “lacked any attempt at balance”, were “irresponsible and could alarm viewers needlessly”, and contained “numerous errors” (Anonymous, 2010a). Frequent editorials in agriculture trade magazines referenced Dr. H. Scott Hurd‟s response outlining the limitations in the CBS reporting (Hurd, 2010), and it appears that the news investigations focused on
Antimicrobial Resistance and the Use of Antibiotics in the Dairy Industry 49
a number of unsubstantiated claims, used provocative or emotive language, and lacked sufficient scope to do justice to this complicated issue.
While dairy production practices were not implicated in these recent reports, consumer concerns regarding food safety, antimicrobial use, and antimicrobial resistance clearly impact the dairy industry.
The Preservation of Antibiotics for Medical Treatment Act (PAMTA, H.R. 1549) was introduced by Congresswoman Louise M. Slaughter (D-NY 28
district) in the 111 th session of the U.S. Congress. Representative Slaughter,
frequently described as “the only microbiologist in Congress” holds a Bachelor of Science degree (1951) in Microbiology and a Master of Science degree (1953) in Public Health from the University of Kentucky. A Senate version of the PAMTA (S. 691) was introduced by Senators Edward Kennedy (D-MA) and Olympia Snowe (R-ME) in this session of Congress. Previous Senate and House versions of the PAMTA have been introduced in each of the 3 Congressional sessions since 2003. In each of the prior sessions the legislation never progressed out of Committee. The current legislation has 127 co-sponsors (out of 435 representatives in the House) where it has been referred to the Committee on Energy and Commerce, and the Committee on Rules. There are 18 co-sponsors of PAMTA in the Senate where it is currently in the Health, Education, Labor and Pensions Committee.
The intent of the current legislation is to phase out non-therapeutic use of medically important antimicrobials in livestock. In other words, with passage of the legislation, antimicrobials identified as identical or closely related to drugs used in human medicine would be withdrawn from use in food animals at sub-therapeutic levels, eliminating antibiotic use in feed or water for growth promotion (i.e. „feed efficiency, weight gain‟) or prophylaxis (i.e. „routine disease prevention‟). This is not a new legislative issue, for example the Antibiotic Preservation Act and the Antibiotic Protection Act were introduced in 1980 and 1984, respectively. House committee hearings were held in 2009 and included testimony from internationally recognized human and veterinary health experts, federal food safety regulators, and national food supply representatives (copies of testimony are available at Congressional web sites) (Anonymous 2010b). More than 375 organizations have endorsed the PAMTA including the American Medical Association, American Academy of Pediatrics, American Public Health Association, the Union of Concerned Scientists, and the Humane Society of the United States (Anonymous 2010c). Individuals and organizations testifying in support of the legislation stated that there is a clear link between feeding of low doses of antimicrobials in food animals and human infections with antibiotic resistant pathogens. National organizations, including the American Veterinary Medical Association, oppose the “legislation because it would increase animal disease and death - an
unfortunate and unintended consequence - without assurance of improving human health” and is neither “risk-based” nor “based upon the science supporting the issue” (Anonymous 2010d). A review of the conflicting „science-based‟ testimony demonstrates that attributing human illness caused by antimicrobial resistant pathogens to antimicrobial use in food animals and specifically to routine feeding of subtherapeutic antibiotics is complex and controversial. The truth is that it is not clear what extent low dose use of antibiotics in food animals can contribute to the risk of human foodborne infections.
It is widely acknowledged that antimicrobial resistance is a significant public health concern. The issue is whether current antimicrobial use practices in food animal production are contributing to the problem of antimicrobial resistance in humans to an extent that warrants limiting or discontinuing subtherapeutic use in food animals for drugs that are used to treat human disease.
The U.S. Food and Drug Administration (FDA) regulates human and veterinary drugs. The FDA Center for Veterinary Medicine (CVM) is specifically tasked with regulating manufacture and distribution of food additives and drugs that will be given to animals. Two FDA guidance documents are relevant to the issue of antimicrobial use in animals and antimicrobial resistance. Guidance #152 addresses methods to evaluate the safety of antimicrobial new animal drugs with regard to their microbiological effects on bacteria of human health concern. The guidance document outlines a risk assessment approach for evaluating antimicrobial resistance developing from use of antimicrobial drugs in food producing animals, with a focus on food-borne bacteria that may be transmitted to humans through the consumption of animal derived foods (Anonymous, 2010e). C