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A story in Science Daily today talks about the effect that antibiotics used in animals has had on humans. Or rather, on antibiotic-resistant bacteria which are dangerous to humans.
The increasing production and use of antibiotics, about half of which is used in animal production, is mirrored by the growing number of antibiotic resistance genes, or ARGs, effectively reducing antibiotics’ ability to fend off diseases — in animals and humans.
Now this is hardly news. Concerns over unchecked use of antibiotics in farm animals have been raised for decades. The antibiotics have been working their way through the system and back into the environment where they came back to haunt us. As noted in this story,
Waters polluted by the ordure of pigs, poultry, or cattle represent a reservoir of antibiotic resistance genes, both known and potentially novel. These resistance genes can be spread among different bacterial species by bacteriophage, bacteria-infecting viruses, according to a paper in the October Antimicrobial Agents and Chemotherapy.
“We found great quantities of bacteriophages carrying different antibiotic resistance genes in waters with fecal pollution from pigs, cattle, and poultry,” says Maite Muniesa of the University of Barcelona, Spain, an author on the study. “We demonstrated that the genes carried by the phages were able to generate resistance to a given antibiotic when introduced into other bacteria in laboratory conditions,” says Muniesa.
The Animal Health Institute assures us antibiotics are necessary to keep us safe:
Because antibiotic resistance is a public health concern, several layers of protection have been put in place to ensure that animal antibiotics do not affect public health.
But our concerns isn’t as great here as it is with one of our primary food suppliers: China. As Science Daily reports:
A study in the current issue of the Proceedings of the National Academy of Sciences shows that China — the world’s largest producer and consumer of antibiotics — and many other countries don’t monitor the powerful medicine’s usage or impact on the environment.
On Chinese commercial pig farms, researchers found 149 unique ARGs, some at levels 192 to 28,000 times higher than the control samples…
Pretty scary. Environment Canada has commented on how antibiotics and other drugs fed to animals get into the environment:
The primary contaminants associated with manure include nitrate and ammonia, coliform bacteria, phosphorus, endocrine disrupters and other animal pharmaceuticals. Both the land use and waste management practices commonly employed on farms throughout Canada have impaired the quality of water resources on a regional basis (Rudolph et al. 1998). In a recent survey of farm drinking wells in Ontario, approximately one well in three was found to contain at least one contaminant commonly associated with agricultural activities, including nitrate or bacteria…
The risk is that these antibiotic-resistant microbes spread easily and rapidly, sharing their AR genes with other microbes:
Daily exposure to antibiotics, such as those in animal feed, allows microbes carrying ARGs to thrive. In some cases, these antibiotic resistant genes become highly mobile, meaning they can be transferred to other bacteria that can cause illness in humans. This is a big concern because the infections they cause can’t be treated with antibiotics.
ARGs can reach the general population through food crops, drinking water and interactions with farm workers. Because of this undesirable cycle, ARGs pose a potential global risk to human health and should be classified as pollutants, said Tiedje, an MSU AgBioResearch scientist.
The genes concentrate in sewage treatment plants, which become reservoirs of them, says this story:
Water discharged into lakes and rivers from municipal sewage treatment plants may contain significant concentrations of the genes that make bacteria antibiotic-resistant. That’s the conclusion of a new study on a sewage treatment plant on Lake Superior in the Duluth, Minn., harbor that appears in ACS’ journal Environmental Science & Technology.
Timothy M. LaPara and colleagues explain that antibiotic-resistant bacteria — a major problem in medicine today — are abundant in the sewage that enters municipal wastewater treatment plants. Treatment is intended to kill the bacteria, and it removes many of the bacterial genes that cause antibiotic resistance. However, genes or bacteria may be released in effluent from the plant. In an effort to determine the importance of municipal sewage treatment plants as sources of antibiotic resistance genes, the scientists studied releases of those genes at the Duluth facility.
These genes can be transferred to humans and affect our health. A 2010 story in Science Daily noted one growing impact on human health:
Genes that make bacteria resistant to antibiotics can be transferred between humans and other animals, say researchers writing in this month’s issue of the Journal of Medical Microbiology. The findings will help health experts to assess how using antibiotics in food-producing animals can affect the treatment of common human infections.
Scientists from the Carol Yu Centre for Infection at the University of Hong Kong examined Escherichia coli bacteria responsible for causing human urinary tract infections (UTIs) and bacteria in faecal samples from humans and food-producing animals. They found an identical gene for antibiotic resistance was present in all the samples in similar proportions and locations, suggesting that the gene is likely to be transferred between bacteria residing in different hosts.
The gene, called aacC2, encodes resistance to a commonly-used antibiotic gentamicin and was found in approximately 80% of human and animal samples. What is more, this gene was found on sections of DNA that are known to swap between different bacterial populations. Both these factors, combined with the identical gene sequences led the researchers to suggest that aacC2 can transfer between separate populations of bacteria that colonise different species.
E. coli is responsible for 75-95% of human urinary tract infections. Surveys in recent years have shown that antibiotic resistance in this bacterium is increasing, making infections increasingly difficult to treat.
This seems to be a bigger problem for women than for men, according to this 2010 story:
Chicken sold in supermarkets, restaurants and other outlets may place young women at risk of urinary tract infections (UTI), McGill researcher Amee Manges has discovered. Samples taken in the Montreal area between 2005 and 2007, in collaboration with the Public Health Agency of Canada and the University of Guelph, provide strong new evidence that E. coli (Escherichia coli) bacteria originating from these food sources can cause common urinary tract infections.
As Greatist notes in this piece, the use of antibiotics in livestock is increasing rapidly:
…the use of antibiotics in livestock may be expanding at a greater rate than the meat industry itself. While the American Meat Institute reported a 0.2 percent increase in meat and poultry production in 2011 compared to 2010, antibiotic consumption jumped 2 percent over the same time period — suggesting meat production might be relying more heavily on antibiotics. All told, the livestock industry now uses nearly four-fifths of the antibiotics administered in the U.S.
The graphic reveals that human antibiotic use has leveled off at below eight billion pounds a year. Meanwhile, meat and poultry farms have been using up record numbers of the stuff each year — reaching a new high of almost 29.9 billion pounds in 2011.
About 80% of all the antibiotics produced in the USA are being fed to animals.
The widespread antibiotic use isn’t just harming us. It’s harming our entire environment. Antibiotic-resistant bacteria are showing up in soil, according to this story:
A team of scientists in the United Kingdom and the Netherlands are reporting disturbing evidence that soil microbes have become progressively more resistant to antibiotics over the last 60 years. Surprisingly, this trend continues despite apparent more stringent rules on use of antibiotics in medicine and agriculture, and improved sewage treatment technology that broadly improves water quality in surrounding environments.
There is a lot more to write and research here, but I’ll leave this here for now with this quote from a story in The Guardian last fall:
The overuse of antibiotics in animal agriculture and medicine is putting human lives at unnecessary risk and driving up medical costs, according to a group of group of 150 scientists that includes a former head of the Food and Drug Administration (FDA)… a growing body of research supported the conclusion that overuse of antibiotics in animal agriculture is fueling a health crisis. One statement cited a study which estimated that antibiotic-resistant infections cost $20bn annually to hospitals alone.
So doomsday may yet be waiting in the wings… or in the soil, the water, and on our dinner plates.
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