Antibiotic-resistant enterococci and fecal indicators in surface water and groundwater impacted by a concentrated swine feeding operation.
Sapkota, A, F Curriero, K Gibson and K Schwabb. 2007.
Environmental Health Perspectives, in press.
http://www.environmentalhealthnews.org/ ... aetal.html
Synopsis by Dr. Edward Orlando and Wendy Hessler
Whole article free at: Antibiotic-resistant enterococci and fecal indicators in surface water and groundwater impacted by a concentrated swine feeding operation.
http://www.ehponline.org/members/2007/9770/9770.pdf
Context
At the heart of the issue is how much antibiotic use in animals influences antibiotic resistance in humans. Although bacterial resistance in people is primarily due to over prescribing of antibiotics, resistant strains from animals can transfer to people through contact at work, by eating contaminated foods or by drinking contaminated water. This study brings to light how CAFOs can pollute ground and surface waters with antibiotic resistant bacteria possibly exposing people to the microbes.
Bacterial resistance to antibiotic drugs is a big concern and a growing problem for large-scale pig yards (known as concentrated animal feedlot operations, or CAFOs) and the people who live near them. Sapkota et al. report that antibiotic resistant bacteria in both surface and groundwater is higher down stream from a swine feeding operation in the Mid-Atlantic region of the United States. The water sources below the swine feedlot also contained higher concentrations of the three types of intestinal bacteria studied – enterococci, fecal coliform and E. coli (Escherichia coli) – than the surface and groundwater tested above the facility.
The degree of antibiotic resistance varied depending on the water sample tested.
The study is important because it is one of only a few comparing the amount of fecal bacteria and the antibiotic resistance of the bacteria in surface and groundwater above and below a swine concentrated animal feeding operation or CAFO. The results show that waste from a swine CAFO can contribute antibiotic-resistant fecal bacteria to natural water systems.
Antibiotics are given to animals to increase their growth. Intestinal bacteria can become resistant to the drugs. The microbes leave the animal in fecal matter and can get into the environment through leaking storage pits and runoff from fields when manure is used as a fertilizer. Humans may become ill or need longer or more potent antibiotic treatment if they are exposed to the resistant microbes.
Although the European Union banned use of antibiotics for growth promotion in January 2006, the United States has not. The US Food and Drug Administration, the government agency that regulates antibacterial use in animals, does not have accurate information about what kinds, how much and where antibiotics are being used across the country. It is estimated, though, that animals raised for food in the US are given 25 million pounds of antibiotics annually just to promote growth and over 10 million pounds of antibiotics in swine production alone (Gilchrist et al. 2007). Today, most animal antibiotics are available over the counter and each farmer decides how they will be used. But, with changing agricultural practices – CAFOs are so large and environmentally detrimental – many are questioning that wisdom and scrutinizing the self-governing approach.
What did they do?
From 2002 – 2004, Sapkota et al. collected 28 surface and groundwater samples from a pond, streams and wells located up- and down stream of a swine CAFO. They examined the samples for three types of bacteria found in animals and people: fecal coliformes, E. coli and enterococci (several species). Fecal coliformes are rod-shaped gut bacteria found in animals and people, whereas enterococci are spherical-shaped bacteria.
They tested resistance to five antibiotics: erythromycin, tetracycline, clindamycin, virginiamycin, and vancomycin. All except vancomycin are FDA approved for swine production in the United States.
To compare anti-biotic resistance among bacteria obtained from different sampling locations, Sapkota et al. determined the lowest dose of antibiotic that was sufficient to prevent bacterial growth. This is called the minimal inhibitory concentration (MIC).
What did they find?
Bacterial levels were much higher downstream of the feed-lot, both in surface and groundwater. Median concentrations of enterococci species, E. coli, and fecal coliform were 17-, 11-, and 33-fold greater in the surface waters and 4-, 11-, and 20-fold greater in the groundwater downstream of the swine CAFO.
With few exceptions, bacteria downstream of the feedlot had higher resistance to antibiotics. For example, the dose of erythromicin needed to prevent growth in enterococci was 128-fold higher for bacteria collected in groundwater downstream compared to upstream.
Sapkota et al. also determined the percentage of Enterococcus species that were resistant to the different antibiotics, and compared upstream and downstream percentages. Six of ten comparisons showed higher resistance downstream. Of those, 2 were statistically significant (Erythromycin in groundwater and surface water) while 2 were marginally significant (Clindamycin in surface water and Tetracyclin in groundwater). Three of ten had higher percentages of the upstream samples, but only 1 was statistically significant (Clindamycin in groundwater).
A combination of economic pressure to control the costs of meat production in developed nations and a rapidly growing demand for meat in developing nations is changing the traditional agricultural practices of raising livestock (Naylor et al. 2005). In the past, beef cattle, dairy cows, swine, poultry and other livestock were fed mainly by grazing in the fields and supplemented with farm-raised grain. Animal waste, in turn, was used to fertilize the fields and provide needed nutrients and humus to the crops. Today, there is a growing trend to centralize and concentrate the husbandry of livestock in animal feeding operations, where livestock are housed in enclosed buildings or fenced enclosures and food is brought to them (Naylor et al. 2005; US EPA 2003).
In the United States, animal feeding operations of a certain size (livestock specific), or with known connections to surface waters or potential to discharge waste, are called CAFOs. There is a growing concern for the environmental impact of CAFOs (US EPA 2003, Gilchrist et al. 2007). CAFOs are relatively large agricultural units that raise animals under high density and often under controlled environmental conditions. CAFOs are defined by the type of animal raised and how the animals are housed, but include commonly raised agricultural animals such as beef cattle, dairy cows, poultry and swine.
Unless you live near a CAFO, it is perhaps difficult to understand how these large feedlots impact the areas next to them. In the Midwest, and areas of the Mid-Atlantic, the Carolinas, and California in the United States, CAFOs containing thousands to hundreds of thousands of beef cattle or dairy cows, swine or poultry are impacting the environment and have the potential to negatively affect human health. As the source of this impact, the animal waste contains natural and synthetic hormones, nutrients such as nitrates and phosphates, metals, antibiotics, antibiotic resistant bacteria, dust and odor (Hamscher et al. 2003; Naylor et al. 2005)
The concentration of animals in a small area increases the likelihood of them developing and transmitting disease. To reduce losses due to disease, farmers often treat livestock with prophylactic antibiotics. Overuse and misuse of these antibiotics has raised concerns for the development of resistant strains of intestinal tract bacteria that could spread into surface and groundwater from leaking animal waste storage pits or from waste applied to the land.
What does it mean?
Sapkota et al. report elevated concentrations of enterococci, E. coli and fecal coliform – all indicators of fecal contamination in the surface and groundwater adjacent to a swine CAFO. Furthermore, the enterococci species generally displayed higher resistance to four antibiotics approved by the FDA for swine production. This study shows that CAFOs do indeed have the potential to not only be a source of nutrients, hormones, dust, and odor, but may lead to the presence of antibiotic resistant bacteria in the surface and groundwater abutting these facilities.
The researchers have demonstrated a probable link from CAFOs to surface and groundwater contamination with antibiotic resistant bacteria, but point out that the study does not prove a linkage to the adjacent swine CAFO. The researchers were not able to confirm the use of the antibiotics used in this study by the owners of the swine CAFO nor were they able to get permission to collect up gradient surface water from the stream that was above the swine CAFO as this was on the farmer’s property and unavailable to the researchers.
This study while imperfect, demonstrates that CAFOs can be sources of antibiotic resistant enteric bacteria that can lead to compromised environmental and potentially human health in ecosystems and populations adjacent to CAFOs.
Resources:
Centers for Disease Control and Prevention. Antibiotic and antimicrobial resistance. http://www.cdc.gov/drugresistance/
Gilchrist M, C Greko, D Wallinga, G Beran, D Riley and P Thorne. 2007. The potential role of concentrated animal feeding operations in infectious disease epidemics and antibiotic resistance. Environmental Health Perspectives 115(2):313-316.
http://www.pubmedcentral.nih.gov/articl ... id=1817683
Hamscher G, HT Pawelzick, S Sczesny, H Nau and J Hartung. 2003. Antibiotics in dust originating from pig-fattening farm: a new source of health hazard for farmers? Environmental Health Perspectives 111(13):1590-1594.
http://www.ehponline.org/docs/2003/6288/abstract.html
Naylor R, H Steinfeld, W Falcon, J Galloway, V Smil, E Bradford, et al. 2005. Losing the links between livestock and land. Science 2005:1621-1622.
http://www.sciencemag.org/cgi/content/s ... /5754/1621
Woodman, R. 1999. Overuse of animal antibiotics threatens human health. British Medical Journal. 319(7209): 536.
http://www.pubmedcentral.nih.gov/articl ... id=1116432
US Environmental Protection Agency. 2003. National pollution discharge elimination system permit regulation and effluent limitation guidelines and standards for concentrated animal feeding operations (CAFOs). Final Rule. Federal Register, February 12, 2003. 68 (29):7175-7274.
http://www.epa.gov/fedrgstr/EPA-WATER/2 ... /w3074.htm
US Food and Drug Administration. Antibiotic resistance.
http://www.fda.gov/oc/opacom/hottopics/anti_resist.html
CAFOs and antibiotic resistance in the news
18 May - CAFOs increase antibiotic resistance in bacteria in downstream waters. Scientists report that bacterial resistance to antibiotics important for fighting human disease is heightened in ground and surface waters downstream of a factory pig farm. Environmental Health News.
http://www.environmentalhealthnews.org/ ... aetal.html
28 December - Big farms have big impacts--and solutions? Farms that raise poultry, swine, and cattle at an industrial scale also have industrial kinds of environmental impacts Environmental Science & Technology.
http://pubs.acs.org/subscribe/journals/ ... cafos.html
24 November - Don't Ease Rules For Factory Farms. When does a lame duck stink? When it's Congress, during the last few days that Republicans can prevail, trying to ram through exemptions for the rank odors and discharges from factory farms. Detroit Free Press, Michigan.
(Please note: unable to locate the original source of this article. EH)
17 November - The potential role of CAFOs in infectious disease epidemics and antibiotic resistance. The industrialization of livestock production and the widespread use of non-therapeutic antimicrobial growth promotants has intensified the risk for the emergence of new, more virulent, or more resistant microorganisms. Environmental Health Perspectives.
http://www.ehponline.org/docs/2006/8837/abstract.html
17 May - Many little piggies, handled with care. Russ Kremer, a fifth-generation pig farmer, had an experience that awoke him to the fact of resistance to antibiotics in livestock and the significant health risk it posed to humans. So he went cold turkey. New York Times.
http://select.nytimes.com/gst/abstract. ... 94DE404482
More news about CAFOs
http://www.environmentalhealthnews.org/ ... ext5;CAFOs
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