There is currently a worldwide antibiotic resistance
epidemic affecting patients of all ages, from all walks of life and in all
areas of medicine. This growing public health concern limits treatment options
and makes successful pharmacotherapy much more difficult.
Although hospital use of antimicrobials has been assumed
to generate the highest risk of resistance and transmission, it is interesting
to note that most antimicrobials are actually found in food animal production:
Virtually all animals raised for food in the US today are given antibiotics to
stimulate growth, prevent bacterial infections and maintain viability.
Furthermore, approximately 70% of the antibiotics used in the US every year are
administered to animals raised for food.
The relationship between antibiotics used in agriculture
and human consequences is not a new concern, as the significance of
antimicrobial use in animals and the development and dissemination of
resistance have been debated for many years. In fact, several major health
organizations, including WHO and the AMA, have stated that the farm-animal
industry is contributing to potential unknown long-term risks for humans.
Kathryn Connor, PharmD, BCPS, BCNSP
Unfortunately, there is still no consensus on this
issue, but there is increased public and scientific interest in the
administration of antimicrobials to animals. Regardless of the controversy,
bacterial pathogens of animal and human origin are becoming increasingly
resistant to most frontline antimicrobials, including penicillins,
expanded-spectrum cephalosporins, aminoglycosides, tetracyclines, sulfonamides
and fluoroquinolones, among others.
Mechanisms and implications
The widespread use of sub-therapeutic and therapeutic
antibiotics in food animal production has resulted in the emergence of
antibiotic-resistant bacteria that can be transmitted to humans through the
food chain. The transfer of antibiotic-resistant genes and selection for
resistant bacteria in food animals are often multifactorial and can occur
through a variety of mechanisms, including chromosomal mutations and the
horizontal transfer of resistance determinants from mobile genetic elements.
Furthermore, these concerns extend beyond the
agricultural field into the aquaculture environment: Antibiotics introduced
into water via feed or that are used for the prevention and treatment of
diseases in fish have been found to induce high levels of antibiotic-resistant
bacteria in aquatic ecosystems.
The increasing incidence of antimicrobial-resistant
pathogens has severe implications in the treatment and prevention of infectious
diseases, including the emergence of community-associated methicillin-resistant
Staphylococcus aureus with reservoirs of resistance in humans and
animals in the community. One study at the University of California, Berkeley
also linked eating beef to urinary tract infections in women.
Potential solutions, role of pharmacists
Although research has linked the use of antibiotics in
agriculture to the emergence of antibiotic-resistant foodborne pathogens, it is
still unclear whether this is significant enough to merit further regulation or
restriction. To this end, it is important to accurately assess and evaluate the
interactions between the hospital and community environments; improve
surveillance for community-acquired resistance, including agriculture; and
implement policies that prevent increases in community reservoirs of antibiotic
resistance. Furthermore, scientific strategies aimed at inhibiting efflux pumps
and eliminating plasmids may help restore therapeutic efficacy to antibiotics
and reduce the spread of antibiotic-resistant pathogens through the food chain.
European countries have enacted legislation that
mandates strict criteria for monitoring antimicrobial residues; the development
of fast, reliable, sensitive testing methods is a priority there. Furthermore,
multiple countries outside of the US have enacted or are considering
implementing more stringent restrictions or bans on some types of
antimicrobials used in food animal production. In some cases, these bans appear
to have resulted in decreased prevalence of some drug-resistant bacteria.
Organic farming also deserves due consideration in this
discussion, as its restrictions and additional requirements have shown to
contribute to further effectiveness of antibiotics.
Infectious disease practitioners play a pivotal role in
public health control, research and increased pharmacovigilance, especially in
antibiotic stewardship arguably the most effective tool in staving off
antibiotic resistance. Efforts in antibiotic management and on education and
risk-management in these areas would likely be invaluable to the issues at
hand. Furthermore, opportunities for collaboration between infectious disease
practitioners, regulatory agencies, the agricultural industry, etc., should be
considered. These may include facilitation of appropriate antibiotic management
programs, consistent treatment protocols, communication and outreach efforts
that encourage information flow, including education on lack of forthcoming
antimicrobials in the pipeline, etc.
As effective strategies for control of antimicrobial
resistance are considered, it is crucial that scientific information provide
the foundation for optimizing animal and human health and minimizing risks from
antibiotic-resistant bacteria. Going forward as we consider these issues, it is
likely that a multifactorial approach from many members of the health care
community, including the collaboration of infectious disease practitioners
helping to manage antimicrobials, will be needed to effectively limit the total
amount of antimicrobials to address both animal welfare and public health
For more information:
- Barlow RS. J Appl Microbiol. 2008;104:651-658.
- Bezanson GS. Int J Food Microbiol. 2008;127:37-42.
- Brownlee C. The beef about UTIs. Science News. Jan. 7, 2010.
Accessed April 26, 2011.
- Call DR. Anim Health Res Rev. 2008;9:159-167.
- Diarra MS. Appl Environ Microbiol. 2007;73:6566-6576.
- Diarrassouba F. J Food Prot. 2007;70:1316-1327.
- Fricke WF. Appl Environ Microbiol. 2009;75:5963-5971.
- Ghidán A. Acta Microbiol Immunol Hung.
- Girardi C. Vet Res Commun. 2008;32(Suppl 1):S11-S18.
- Leatherbarrow AJ. Environ Microbiol. 2007;9:1772-1779.
- Mathew AG. Foodborne Pathog Dis. 2007;4:115-133.
- McDermott PF. Anim Biotechnol. 2002;13:71-84.
- McManus PS. Annu Rev Phytopathol. 2002;40:443-65.
- Peng Y. J Dairy Res. 2008;75:491-496.
- Reuters Medical News. Drug-resistant bacteria found in US meat. May
24, 2001. Available at:
www.pmac.net/AM/DR_bacteria.pdf. Accessed April 26, 2011.
- Rezzonico F. Antimicrob Agents Chemother. 2009;53:3173-3177.
- Schwaiger K. Zoonoses Public Health. 2008;55:331-341.
- Silbergeld EK. Med Clin North Am. 2008;92:1391-1407.
- Steinman D. Diet for a Poisoned Planet: How to Choose Safe Foods
for You and Your Family. New York: Harmony Books; 1990.
- Walsh C. Curr Drug Targets. 2008;9:808-815.
- Webster P. Lancet. 2009;374:773-774.
- Yu D. Chemosphere. 2009;76:915-920.
Kathryn A. Connor, PharmD, BCPS, BCNSP, is a clinical
pharmacy specialist and assistant professor of critical care at the University
of Rochester Medical Center. Dr. Connor reports no relevant financial