(Beyond Pesticides, May 18, 2012) A groundbreaking report documents the potential for antibiotics used in the production of corn-based ethanol to contribute to the emergence of antibiotic-resistant bacteria. The potential for the misuse of antibiotics in industrial agriculture to spawn antibiotic-resistant bacteria has long been recognized, but the new report sheds light on a dimension of the problem that has largely gone unnoticed. Entitled Bugs in the System and published by the Institute for Agriculture and Trade Policy (IATP), the report establishes that antibiotic residues found in the by-products of ethanol production are strong enough to promote resistance in pathogenic bacteria when those by-products are fed to livestock. The report points out that for life-threatening bacterial infections in humans, there are no alternatives to antibiotics and that once resistant bacteria develop from antibiotic misuse, we have forever lost an effective treatment for the illness.
For at least two decades, antibiotics have been an important component of the fermentation process used to make ethanol. Corn ethanol is the product of starches broken down into sugars by yeast. The sugars are then fermented and distilled, all of which happens in tanks full of warm water, a perfect environment not only for yeast but also for growing bacteria. Bacterial contamination is a significant problem for ethanol producers, because the bacteria compete with the yeast for sugar and nutrients and outbreaks can cause significant losses in the yield of the ethanol plant, or even halt the fermentation process. To prevent bacterial outbreaks and limit yield losses, many ethanol producers routinely dose fermentation tanks with antibiotics also important to human medicine, like penicillin, erythromycin and tylosin, and virginiamycin.
Fuel isnâ€™t the only product that leaves an ethanol plant. After the ethanol is distilled, the remaining corn mash and liquid slurry is sold either wet or dry as an animal feed, a product known as distillers grains with solubles (DGS) (the solubles are a nutritious, molasses-like liquid created when some of the slurry water is separated from the mash and condensed; itâ€™s typically added back into the distillers grains to boost nutrition values) In the last decade, accompanying the increase in ethanol production, DGS production and sales have exploded. From 2000 to 2010, DGS production increased 1,264 percent, from 2.5 to 34.1 million metric tons per year. The beef industry uses 41 percent of all DGS, the dairy industry consumes 26 percent, 5 percent are fed to swine and 4 percent to poultry while 22 percent are exported for use by meat producers overseas.
In 2010, the U.S. Food and Drug Administration (FDA) collected and analyzed 46 samples â€”18 import samples and 28 domestic samplesâ€” for residues of 12 antibiotics (ampicillin, penicillin G, chlortetracycline, oxytetracycline, tetracycline, clarithromycin, erythromycin, streptomycin, virginiamycin M1, bacitracin A, chloramphenicol, monensin, and tylosin). FDA found four positive samples, three of which did not select for resistance (i.e., allow the susceptible bacteria to die off and the resistant bacteria to thrive) among Campylobacter bacteria (a major cause of food poisoning) or Enterococcus bacteria (resistant strains of which cause significant problems in hospitals). However, FDA recorded erythromycin in the DGS at a level of 0.58 ppm and subsequent testing confirmed that these residues selected for resistance in Enterococcus bacteria. These results indicate that the residues of antibiotics in DGS â€”the predictable result of adding antibiotics to ethanol fermentation vatsâ€” have the potential to cause increased antibiotic resistance impacting the human population.
IATP also demonstrates in the report that that the risk from residue-contaminated DGS is unnecessary because effective non-antibiotic antimicrobial products are widely available to ethanol producers. In fact, POET, the largest ethanol producer in the world, recently announced that all of its 27 plants are antibiotic-free. A small number of those plants are third-party certified antibiotic-free, a step that allows the company to market antibiotic-free DGS to the layer hen industry, where DGS with antibiotic residues are prohibited.
The USDA organic certification program prohibits feeding DGS to organically raised livestock. The producer of an organic livestock operation must provide livestock with a total feed ration composed of agricultural products, including pasture and forage, that are organically produced and handled by operations certified to the NOP. The only exceptions to these requirements are synthetic feed additives and supplements which have been approved after rigorous scrutiny by the National Organic Standards Board (NOSB). For example, synthetic trace minerals and vitamins are allowed as synthetic feed additives in organically managed livestock. The organic livestock feed standards also prohibit the feeding of mammalian or poultry slaughter by-products to mammals or poultry. Additionally, USDA has implemented the comprehensive NOSB recommendation that requires organically managed ruminants to receive a substantial portion of their feed ration from pasture.
Currently, organic farmers growing apples and pears are allowed to use the antibiotics streptomycin and tetracycline to control a fruit tree disease called fire blight. The National Organic Standards Board, the principle advisory body responsible for advising USDA on its organic certification program, has been increasingly reluctant to extend these allowances due to concerns about accelerated resistance in pathogenic organisms and the availability of effective cultural practices and biological treatments for managing fire blight. The NOSB has recommended phasing out tetracycline and streptomycin to manage fire blight in pear and apple trees in October 2014 with the expectation that alternative production options will be adopted.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.