Illinois Correspondent

PEORIA, Ill. — Research into antibiotic resistance by the University of Illinois at Champaign-Urbana has linked the use of the antibiotic tetracycline, widely used in swine production, to the presence of antibiotic resistant genes in groundwater.

Published in the most recent issue of Applied and Environmental Biology, the study revealed the genes “move” through populations of different species of bacteria and sometimes leak from waste lagoons into groundwater. The study was among the first to track antibiotic resistance genes rather than the organisms that host them.

“People are already dying of antibiotic resistant infections. Any factor worsening the epidemic of such infections is of great concern,” stated Dr. David Wallinga, director of the food and health program for the Institute for Agriculture & Trade Policy and a member of the Keep Antibiotics Working Coalition.

“And the science now clearly implicates agricultural overuse of antibiotics, as with the routine addition of antibiotics to hog feed, with worsening resistance.”

UoI researchers determined the resistance genes are transferred “like batons” from one bacterial species to another, a conclusion that could have serious implications for antibiotics used to treat human disease. The research team concluded tetracycline resistance genes could lead to resistance to similar antibiotics important to human medicine. Tetracyclines are used to treat serious human infections such as anthrax, chlamydia and urinary tract infections, along with diseases transmitted by ticks, such as Lyme’s Disease.

Researchers extracted bacterial DNA from lagoons and groundwater wells at two hog farms over a period of three years and screened the samples for seven different tetracycline resistance genes. They discovered fluctuating levels of every one of the seven genes for which they screened. They also found the genes were migrating from the lagoons to some of the groundwater wells.

“If the genes are there, potentially they can get into the right organism at the right time and confer resistance to an antibiotic that’s being used to treat (human) disease,” remarked R.I Mackie, the study’s principal investigator and a professor in the UoI Department of Animal Sciences.

Wallinga said when it comes to resistance, bacteria are indiscriminate. “They easily swap the genes that make them impervious to antibiotics, making the threat very real that eventually bugs causing infections in humans will be the ones resistant to treatment,” he said.

“This study is just the latest of many that have shown that using antibiotics routinely in the feed for healthy livestock can ultimately lead to more dangerous bacterial infections in humans.”

Roughly 238,000 animal feeding operations in the United States generate about 500 million tons of manure per year. Groundwater comprises some 40 percent of the public water supply and more than 97 percent of the drinking water used in rural areas, according to UoI researchers.

“What we’re seeing is that the genes can travel a lot faster than the bacteria,” said Mackie. “It’s a matter of getting the DNA into the right organism. It’s a relay race.”

The study noted many genes that confer antibiotic resistance occur naturally in the environment. Tetracycline is itself a bacterial product, employed by Streptomyces bacteria long before humans discovered its usefulness, researchers said.

A group of U.S. lawmakers has proposed federal legislation, “The Preservation of Antibiotics for Medical Treatment Act,” which would phase out the use of antibiotics important to human medicine as animal feed additives, within two years. According to the Keep Antibiotics Working Coalition, the bill has the support of the American Medical Assoc., Infectious Disease Society of America and the American Academy of Pediatrics, among more than 350 health, agricultural and other groups nationwide.

The coalition is comprised of health, consumer, agricultural, environmental, humane and other advocacy groups dedicated to eliminating what they term inappropriate use of antibiotics in food animals. Active members include the Center for Science in the Public Interest, Environmental Defense, Food Animal Concerns Trust, Institute for Agriculture and Trade Policy and Union of Concerned Scientists. The group claims more than nine million members.

The Applied and Environmental Microbiology article on the study is available at www.aem.asm.org and UoI’s account of the study can be accessed at www.news.uiuc.edu

This farm news was published in the Sept. 26, 2007 issue of Farm World, serving Indiana, Ohio, Illinois, Kentucky, Michigan and Tennessee.