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Antibiotics with a side of steak

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This post was chosen as an Editor's Selection for ResearchBlogging.orgWe’re in a sad and weird place in biomedical science. In the 1940’s we got penicillin, in the following 30 years another 13 different classes of antibiotic were introduced. Since 1970 the number of new classes of antibiotic have dropped to a worrying 2. Our most productive research is, simply put,  new ways to arrange the deckchairs on our once proud antibiotic ship that is now well and truly sinking.

This is an awful situation as we are fast approaching a world full of antibiotic-resistant bacteria and no drugs to treat them. While problems do exist in the way we diagnose and treat infectious disease, and there remain issues relating to patient compliance, there is one aspect of our antibiotic use has vastly accelerated, the use of antibiotics in agriculture. The rise of the antibiotic use in food production has resulted in the development of the drug resistant herd and the use of antibiotics as a procedural step in food animal production and agriculture generally has become wide spread in some parts of the world and particularly in the United States.

The US Food and Drug Administration (FDA) has just released a new report outlining the sales data of antibiotics for animal agriculture use in the US. Antibiotic use in food production topped out 13.2 MILLION (!!!) kg of antibiotics last year. This number is up on last years report, the only other report performed by the FDA in this regard, despite claims by the industry that less antibiotic is being used per animal every year. In many ways this reflects the global food demands but it also highlights a very important question, should we be pumping our meat full of antibiotics?

High contrast dollar bill

According to Wikipedia "A USD bill of any denomination weighs 1 gram. There are 454 grams in a pound. One million $1 bills would weigh in at 2,204.62 pounds, or just over 1 ton." By that measure 13.2 million tons of US$1 bills would weigh as much as the antibiotics they bought. Photo Credit: MoneyBlogNewz

The use of antibiotics in industrial food production was introduced as a preventative measure to avoid sickness, allowing more animals to grow to weight and then be shipped off to market. But this results in healthy livestock receiving medication and becoming a breeding ground for antibiotic-resistant strains of many bacterial species including E. coli. Many of the antibiotics are not actually prescribed, in fact for some agricultural uses there is no legal requirement for them to be, which is baffling to say the least as we approach a world with fewer and fewer effective antibiotics.

The effects of antibiotic use can be clearly seen when the US sales data is compared to the European data. In some parts of Europe, the use of antibiotics for “growth promotion” is illegal and in fact the European Parliament recently moved to prevent “prophylactic use” which would eliminate the argument of disease prevention as a cue for antibiotic use. In these parts of Europe the amount of antibiotic sold translates to less than 50mg of antibiotic per kilogram of meat. While in the US the quantity is at least six times that according to Dr. Gail Hansen, senior officer and staff veterinarian for Pew Campaign on Human Health and Industrial Farming, who refers to the World Health Organisation data reproduced below. Careful breakdown of the FDA report also echoes these concerns about prescription as there was an overall increase in antibiotic sales noted but a decrease in the sales of aminoglycosides and cephalosporins which are only available by prescription suggesting a further shift toward prescription independent antibiotic use.

 

Caption accompanying graph from WHO presentation - "Data on consumption collated from different sources that use different ways of estimating the data. Data on meat production was acquired from FAO." Data presented by Dr. Danilo Lo Fo Wong on Jan 25th, 2011

Dr. Hansen also points out that research indicates strongly that the way antibiotics are being distributed to livestock is driving up resistance. Routinely antibiotics are delivered via the feed to the animals. Because of this they receive inconsistent and generally lower than prescription dosages of antibiotic, the perfect situation if you are trying to generate resistance. Antibiotic resistance develops when an antibiotic is used on a population of bacteria. Most of the bacterial population will die but any that survive due to random mutations that they harbor will pass them onto their descendants, who will pass them on to theirs, and so on producing antibiotic-resistant strains. Standard administered doses can overwhelm even those mutants who contain the saving mutations and better yet many antibiotics are given in combinations as the likelihood of a single bacterium harbouring saving mutations to multiple antibiotics is very rare, but extended periods of low dosage with single antibiotics provides those capable of surviving with enough of an chance to survive and repopulate, even in the presence of the antibiotic. Worse than this, the presence of a single antibiotic resistant strain can result in the rise of multiple species exhibiting resistance as many bacterial species have the capacity to share genes with each other.

The use of antibiotics in agricultural food production and their effects are not just limited to the agricultural industry. The antibiotics used in food production are in many cases the same or at least very closely related to the drugs  you take when you are sick so the generation of antibiotic-resistant mutants in livestock also reduces the effectiveness of the drugs you take for your illnesses. Antibiotics are a precious and finite resource where every use potentially lowers the effectiveness for everyone in the community.

One of the concerns that is often raised with antibiotic use in agricultural food production is residual antibiotic persisting in the animal throughout the process that converts it into the steak on the shelf. Dr. Hansen suggests this is less of a problem than people portray as so little antibiotic persists and what does is not toxic. Agriculturalists must follow mandatory antibiotic withdrawl times before slaughter which helps, but even still some can remain in products such as milk.

One of Dr Hansen’s main concerns instead is that the vast majority of the antibiotic pass straight through the animal and exits in the feces. The feces then sits in the fields and continues to select for antibiotic resistance in the environment and acts as a pool to re-infect new animals. This cycle makes it even more difficult to reduce the number of antibiotic-resistant organisms in the agricultural process.

So what can we do? Lowering the amount of antibiotics used non-therapeutically in meat production may reduce the number of antibiotic-resistant organisms in the environment, so it seems we must try lower usage. Lowering the number of antibiotic-resistant organisms will have huge flow on effect for human health and may slow the march to our antibiotic-free future. Consumers are key as they drive demand, argues Dr. Hansen. Specific labels exist in the US for meat grown without extraneous use of antibiotics so consumers can be informed about the path their meat took from pasture to plate. Butchers and restaurants should also be aware of the origins of their meat, so ask them. Even Chicago’s public school system has begun purchasing and serving chicken raised without antibiotics to students in 473 schools so there is much that can be done.

Cow

Photo Credit: Simon Aughton

It’s not impossible to turn this around but it does need a swift change in thinking. Many argue that without antibiotics in agricultural food production the industry would fail but we already have the solution to this. Vaccines are very safe and much more effective than antibiotics. They are also significantly cheaper in the long term.  Changes in animal husbandry practices and improved hygiene have also proved to be viable alternatives to antibiotic use. All we need is the political will to tackle this problem and a cohesive message to reach the agricultural industry to ensure the effectiveness of antibiotics for you and me, the cows, pigs and chooks persists into the future.

 

References

Antimicrobials Sold or Distributed for Use in Food-Producing Animals

EU Parliament Votes To Oppose Most Farm Antibiotic Use

Marshall, B., & Levy, S. (2011). Food Animals and Antimicrobials: Impacts on Human Health Clinical Microbiology Reviews, 24 (4), 718-733 DOI: 10.1128/CMR.00002-11

James Byrne About the Author: Dr James Byrne has a PhD in Microbiology and works as a science communicator at the Royal Institution of Australia (RiAus), Australia's unique national science hub, which showcases the importance of science in everyday life. Follow on Twitter @JB_blogs.

The views expressed are those of the author and are not necessarily those of Scientific American.



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  1. 1. S.E. Gould (labrat) 3:48 am 11/17/2011

    Antibiotics in feed being taken in at lower levels than intended means that instead of the evolutionary pressure being “die unless you have a resistance gene” it instead becomes “stay very ill until one of your rare offspring finally gains a useful mutation and takes over” As you can see, this makes resistance much more likely to evolve.

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  2. 2. maysaa 9:48 am 11/18/2011

    There has reports mentioned that antibiotic production is a feature of several kinds of soil bacteria and fungi and may represent a survival mechanism whereby organisms can eliminate competition and colonize a niche (Jensen et al., 1997; Talaro and Talaro, 1996). Although both fungal and bacterial species are known to produce antibiotics, fungi tend to produce mostly broad-spectrum activities but more antibiotics are produced by bacteria (Salyers and Whitt, 2001).
    Oskay et al. (2004) showed that actinomycetes have the capability to synthesize many different biologically active secondary metabolites such as antibiotics, herbicides, pesticides, anti-parasitic, and enzymes like cellulase and xylanase used in waste treatment. Actinomycetes are the most widely distributed groups of microorganisms in nature. They are attractive, bodacious and charming filamentous gram-positive bacteria. They make up in many cases, especially under dry alkaline conditions, a large part of the microbial population of the soil (Athalye et al., 1981; Goodfellow and Williams, 1983; Lacey, 1973 and 1997; Nakayama, 1981; Waksman, 1961). Based on several studies among bacteria, the actinomycetes are noteworthy as antibiotic producers, making three quarters of all known products, the Streptomyces are especially prolific (Lacey, 1973; Lechevalier, 1989; Locci, 1989; Saadoun and Gharaibeh, 2003; Waksman, 1961).
    Actinomycetes can be isolated from soil and marine sediments. The soil actinomycetes have been important sources of antibiotics. For example, about 1% of soil actinomycetes produce streptomycin, first discovered in the 1940s, whereas daptomycin producers were discovered only after screening nearly 107 actinomycetes. Most of the antibiotics in use today are derivatives of natural products of actinomycetes and fungi (Butler and Buss, 2006; Newman and Cragg, 2007). Antibiotics produced by actinomycetes have been evolving for ~1 billion years (Baltz, 2005 and 2006), and fitness has been tested by the ability to penetrate other microbes and inhibit the target enzymes, macromolecules or macromolecular structures (Baltz, 2008).
    The ability of actinomycetes to make secondary metabolites with different useful properties is widely exploited. Two thirds of the antibiotics produced by microorganisms are made by actinomycetes. In particular, genus of Streptomyces is remarkable in this aspect, representing about 80% of the actinomycete antibiotics (Borodina et al., 2005).
    Microbial natural products are the origin of most of the antibiotics. The discovery of penicillin in the 1940s was followed by the discovery of a huge number of antibiotics from microbes, in particular from members of the actinomycetes and fungi. Actinomycetes have traditionally been the most prolific group in antibiotic production. Fungi are another rich source of antibiotics (Peláez, 2006).
    Anupama et al. (2007) reported that actinomycetes have been isolated from different soils, plant materials, water and marine sediments (Mincer et al., 2002). At least 90% of the population among actinomycetes isolated from soils have been reported to be Streptomyces spp. Among microorganisms, actinomycetes are the important source for bioactive metabolites especially antibiotics (Bérdy, 2005).
    If you need to read more read this book

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