Antibiotics with a side of steak

We?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 has dropped to a worrying 2. Since then we have found new ways to arrange the deckchairs on our once proud antibiotic ship but we are 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. One aspect of our antibiotic use has vastly accelerated the rise of the antibiotic resistant herd, the use of antibiotics as a procedural step in food animal production and agriculture generally.

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. 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?

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 animals getting sick, allowing more to grow to weight and be shipped off to market. But this resulted in healthy livestock receiving medication and becoming a breeding ground for antibiotic-resistant strains of many bacterial species including E. coli. Many antibiotics are not actually prescribed and in fact do not legally need 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, in the US it 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?referred?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 the way antibiotics are being distributed to livestock is driving resistance. Routinely antibiotics are delivered via the feed to animals. Because of this they receive inconsistent and generally lower than prescription dosages of antibiotic, the perfect situation for the generation of resistance. Antibiotic resistance develops when an antibiotic is used on a population of bacteria. Most of the population will die but any that do survive due to random mutations that they harbor will pass them onto their descendants producing antibiotic-resistant strains. Standard administered doses can overwhelm even those mutants who contain the saving mutations but extended low dosage provides those capable of surviving with enough of an advantage 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 agricultural use of antibiotics 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 are often raised with antibiotic use in agricultural food production is residual antibiotic surviving in the animal throughout the process that turns it into the steak on the shelf. Dr. Hansen suggests this is less of a problem than people portray as so little antibiotic survives and what does is not toxic. Growers must follow mandatory antibiotic withdrawl times before slaughter which helps this but event still some can remain in products such as milk. One of Dr Hansen?s main concerns however is that the vast majority of the antibiotic pass straight through the animals 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 to lower use. Lowering the number of antibiotic-resistant organisms will have huge follow 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.

Photo Credit: Simon Aughton

It?s not impossible to turn this around but it does need a shift in thinking. Many argue that without antibiotics agricultural food production would stop 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 to ensure the?effectiveness?of antibiotics persists into the future.

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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

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